LUCENE-9322: Add Lucene90 codec, including VectorFormat

This commit adds support for dense floating point VectorFields.
The new VectorValues class provides access to the indexed vectors.

.dir-locals.el

@@ -0,0 +1,3 @@
+;; set up Lucene style for emacs
+((java-mode . ((c-basic-offset . 2))))
+

.gitignore

@@ -7,7 +7,8 @@ build
 dist
 lib
 test-lib
-/*~
+*~
+.#*
 /build.properties
 /.idea
 lucene/**/*.iml

gradle/documentation/render-javadoc.gradle

@@ -157,7 +157,8 @@ configure(project(":lucene:backward-codecs")) {
         "org.apache.lucene.codecs.lucene60",
         "org.apache.lucene.codecs.lucene80",
         "org.apache.lucene.codecs.lucene84",
-        "org.apache.lucene.codecs.lucene86"
+        "org.apache.lucene.codecs.lucene86",
+        "org.apache.lucene.codecs.lucene87"
     ]
   }
 }

lucene/backward-codecs/src/java/org/apache/lucene/codecs/lucene80/Lucene80Codec.java

@@ -20,6 +20,7 @@ import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.CompoundFormat;
 import org.apache.lucene.codecs.DocValuesFormat;
 import org.apache.lucene.codecs.FieldInfosFormat;
+import org.apache.lucene.codecs.VectorFormat;
 import org.apache.lucene.codecs.LiveDocsFormat;
 import org.apache.lucene.codecs.NormsFormat;
 import org.apache.lucene.codecs.PointsFormat;
@@ -128,4 +129,9 @@ public class Lucene80Codec extends Codec {
   public final NormsFormat normsFormat() {
     return normsFormat;
   }
+
+  @Override
+  public final VectorFormat vectorFormat() {
+    return VectorFormat.EMPTY;
+  }
 }

lucene/backward-codecs/src/java/org/apache/lucene/codecs/lucene84/Lucene84Codec.java

@@ -23,6 +23,7 @@ import org.apache.lucene.codecs.CompoundFormat;
 import org.apache.lucene.codecs.DocValuesFormat;
 import org.apache.lucene.codecs.FieldInfosFormat;
 import org.apache.lucene.codecs.FilterCodec;
+import org.apache.lucene.codecs.VectorFormat;
 import org.apache.lucene.codecs.LiveDocsFormat;
 import org.apache.lucene.codecs.NormsFormat;
 import org.apache.lucene.codecs.PointsFormat;
@@ -136,6 +137,11 @@ public class Lucene84Codec extends Codec {
     return new Lucene60PointsFormat();
   }
 
+  @Override
+  public VectorFormat vectorFormat() {
+    return VectorFormat.EMPTY;
+  }
+
   /** Returns the postings format that should be used for writing
    *  new segments of <code>field</code>.
    *

lucene/backward-codecs/src/java/org/apache/lucene/codecs/lucene86/Lucene86Codec.java

@@ -24,6 +24,7 @@ import org.apache.lucene.codecs.CompoundFormat;
 import org.apache.lucene.codecs.DocValuesFormat;
 import org.apache.lucene.codecs.FieldInfosFormat;
 import org.apache.lucene.codecs.FilterCodec;
+import org.apache.lucene.codecs.VectorFormat;
 import org.apache.lucene.codecs.LiveDocsFormat;
 import org.apache.lucene.codecs.NormsFormat;
 import org.apache.lucene.codecs.PointsFormat;
@@ -136,6 +137,11 @@ public class Lucene86Codec extends Codec {
     return pointsFormat;
   }
 
+  @Override
+  public final VectorFormat vectorFormat() {
+    return VectorFormat.EMPTY;
+  }
+
   /** Returns the postings format that should be used for writing
    *  new segments of <code>field</code>.
    *

lucene/backward-codecs/src/java/org/apache/lucene/codecs/lucene87/Lucene87Codec.java

@@ -31,6 +31,7 @@ import org.apache.lucene.codecs.PostingsFormat;
 import org.apache.lucene.codecs.SegmentInfoFormat;
 import org.apache.lucene.codecs.StoredFieldsFormat;
 import org.apache.lucene.codecs.TermVectorsFormat;
+import org.apache.lucene.codecs.VectorFormat;
 import org.apache.lucene.codecs.lucene50.Lucene50CompoundFormat;
 import org.apache.lucene.codecs.lucene50.Lucene50LiveDocsFormat;
 import org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat;
@@ -137,6 +138,9 @@ public class Lucene87Codec extends Codec {
     return pointsFormat;
   }
 
+  @Override
+  public final VectorFormat vectorFormat() { return VectorFormat.EMPTY; }
+
   /** Returns the postings format that should be used for writing
    *  new segments of <code>field</code>.
    *

lucene/backward-codecs/src/java/org/apache/lucene/codecs/lucene87/package.html

@@ -0,0 +1,42 @@
+<!--
+  Licensed to the Apache Software Foundation (ASF) under one or more
+  contributor license agreements.  See the NOTICE file distributed with
+  this work for additional information regarding copyright ownership.
+  The ASF licenses this file to You under the Apache License, Version 2.0
+  (the "License"); you may not use this file except in compliance with
+  the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+  -->
+
+<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
+<!--
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements.  See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License.  You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+-->
+<html>
+<head>
+   <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
+</head>
+<body>
+Lucene 8.7 file format.
+</body>
+</html>

lucene/backward-codecs/src/resources/META-INF/services/org.apache.lucene.codecs.Codec

@@ -16,3 +16,4 @@
 org.apache.lucene.codecs.lucene80.Lucene80Codec
 org.apache.lucene.codecs.lucene84.Lucene84Codec
 org.apache.lucene.codecs.lucene86.Lucene86Codec
+org.apache.lucene.codecs.lucene87.Lucene87Codec

lucene/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/CreateIndexTask.java

@@ -29,7 +29,7 @@ import org.apache.lucene.benchmark.byTask.PerfRunData;
 import org.apache.lucene.benchmark.byTask.utils.Config;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.PostingsFormat;
-import org.apache.lucene.codecs.lucene87.Lucene87Codec;
+import org.apache.lucene.codecs.lucene90.Lucene90Codec;
 import org.apache.lucene.index.ConcurrentMergeScheduler;
 import org.apache.lucene.index.IndexCommit;
 import org.apache.lucene.index.IndexDeletionPolicy;
@@ -138,7 +138,7 @@ public class CreateIndexTask extends PerfTask {
     if (defaultCodec == null && postingsFormat != null) {
       try {
         final PostingsFormat postingsFormatChosen = PostingsFormat.forName(postingsFormat);
-        iwConf.setCodec(new Lucene87Codec() {
+        iwConf.setCodec(new Lucene90Codec() {
           @Override
           public PostingsFormat getPostingsFormatForField(String field) {
             return postingsFormatChosen;

lucene/codecs/src/java/org/apache/lucene/codecs/simpletext/SimpleTextCodec.java

@@ -21,6 +21,7 @@ import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.CompoundFormat;
 import org.apache.lucene.codecs.DocValuesFormat;
 import org.apache.lucene.codecs.FieldInfosFormat;
+import org.apache.lucene.codecs.VectorFormat;
 import org.apache.lucene.codecs.LiveDocsFormat;
 import org.apache.lucene.codecs.NormsFormat;
 import org.apache.lucene.codecs.PointsFormat;
@@ -46,6 +47,7 @@ public final class SimpleTextCodec extends Codec {
   private final DocValuesFormat dvFormat = new SimpleTextDocValuesFormat();
   private final CompoundFormat compoundFormat = new SimpleTextCompoundFormat();
   private final PointsFormat pointsFormat = new SimpleTextPointsFormat();
+  private final VectorFormat vectorFormat = new SimpleTextVectorFormat();
   
   public SimpleTextCodec() {
     super("SimpleText");
@@ -100,4 +102,9 @@ public final class SimpleTextCodec extends Codec {
   public PointsFormat pointsFormat() {
     return pointsFormat;
   }
+
+  @Override
+  public VectorFormat vectorFormat() {
+    return vectorFormat;
+  }
 }

lucene/codecs/src/java/org/apache/lucene/codecs/simpletext/SimpleTextFieldInfosFormat.java

@@ -30,6 +30,7 @@ import org.apache.lucene.index.FieldInfos;
 import org.apache.lucene.index.IndexFileNames;
 import org.apache.lucene.index.IndexOptions;
 import org.apache.lucene.index.SegmentInfo;
+import org.apache.lucene.index.VectorValues;
 import org.apache.lucene.store.ChecksumIndexInput;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.store.IOContext;
@@ -67,6 +68,8 @@ public class SimpleTextFieldInfosFormat extends FieldInfosFormat {
   static final BytesRef DATA_DIM_COUNT  =  new BytesRef("  data dimensional count ");
   static final BytesRef INDEX_DIM_COUNT =  new BytesRef("  index dimensional count ");
   static final BytesRef DIM_NUM_BYTES   =  new BytesRef("  dimensional num bytes ");
+  static final BytesRef VECTOR_NUM_DIMS =  new BytesRef("  vector number of dimensions ");
+  static final BytesRef VECTOR_SCORE_FUNC = new BytesRef("  vector score function ");
   static final BytesRef SOFT_DELETES    =  new BytesRef("  soft-deletes ");
   
   @Override
@@ -146,13 +149,23 @@ public class SimpleTextFieldInfosFormat extends FieldInfosFormat {
         assert StringHelper.startsWith(scratch.get(), DIM_NUM_BYTES);
         int dimensionalNumBytes = Integer.parseInt(readString(DIM_NUM_BYTES.length, scratch));
 
+        SimpleTextUtil.readLine(input, scratch);
+        assert StringHelper.startsWith(scratch.get(), VECTOR_NUM_DIMS);
+        int vectorNumDimensions = Integer.parseInt(readString(VECTOR_NUM_DIMS.length, scratch));
+
+        SimpleTextUtil.readLine(input, scratch);
+        assert StringHelper.startsWith(scratch.get(), VECTOR_SCORE_FUNC);
+        String scoreFunction = readString(VECTOR_SCORE_FUNC.length, scratch);
+        VectorValues.ScoreFunction vectorDistFunc = distanceFunction(scoreFunction);
+
         SimpleTextUtil.readLine(input, scratch);
         assert StringHelper.startsWith(scratch.get(), SOFT_DELETES);
         boolean isSoftDeletesField = Boolean.parseBoolean(readString(SOFT_DELETES.length, scratch));
 
         infos[i] = new FieldInfo(name, fieldNumber, storeTermVector, 
                                  omitNorms, storePayloads, indexOptions, docValuesType, dvGen, Collections.unmodifiableMap(atts),
-                                 dimensionalCount, indexDimensionalCount, dimensionalNumBytes, isSoftDeletesField);
+                                 dimensionalCount, indexDimensionalCount, dimensionalNumBytes,
+                                 vectorNumDimensions, vectorDistFunc, isSoftDeletesField);
       }
 
       SimpleTextUtil.checkFooter(input);
@@ -172,6 +185,10 @@ public class SimpleTextFieldInfosFormat extends FieldInfosFormat {
   public DocValuesType docValuesType(String dvType) {
     return DocValuesType.valueOf(dvType);
   }
+
+  public VectorValues.ScoreFunction distanceFunction(String scoreFunction) {
+    return VectorValues.ScoreFunction.valueOf(scoreFunction);
+  }
   
   private String readString(int offset, BytesRefBuilder scratch) {
     return new String(scratch.bytes(), offset, scratch.length()-offset, StandardCharsets.UTF_8);
@@ -253,6 +270,14 @@ public class SimpleTextFieldInfosFormat extends FieldInfosFormat {
         SimpleTextUtil.write(out, Integer.toString(fi.getPointNumBytes()), scratch);
         SimpleTextUtil.writeNewline(out);
 
+        SimpleTextUtil.write(out, VECTOR_NUM_DIMS);
+        SimpleTextUtil.write(out, Integer.toString(fi.getVectorDimension()), scratch);
+        SimpleTextUtil.writeNewline(out);
+
+        SimpleTextUtil.write(out, VECTOR_SCORE_FUNC);
+        SimpleTextUtil.write(out, fi.getVectorScoreFunction().name(), scratch);
+        SimpleTextUtil.writeNewline(out);
+
         SimpleTextUtil.write(out, SOFT_DELETES);
         SimpleTextUtil.write(out, Boolean.toString(fi.isSoftDeletesField()), scratch);
         SimpleTextUtil.writeNewline(out);

lucene/codecs/src/java/org/apache/lucene/codecs/simpletext/SimpleTextVectorFormat.java

@@ -0,0 +1,51 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.codecs.simpletext;
+
+
+import java.io.IOException;
+
+import org.apache.lucene.codecs.VectorFormat;
+import org.apache.lucene.codecs.VectorReader;
+import org.apache.lucene.codecs.VectorWriter;
+import org.apache.lucene.index.SegmentReadState;
+import org.apache.lucene.index.SegmentWriteState;
+
+/** For debugging, curiosity, transparency only!!  Do not use this codec in production.
+ *
+ *  <p>This codec stores all data in a single human-readable text file (_N.vec).  You can view this in
+ *  any text editor, and even edit it to alter your index.
+ *
+ *  @lucene.experimental */
+public final class SimpleTextVectorFormat extends VectorFormat {
+  
+  @Override
+  public VectorWriter fieldsWriter(SegmentWriteState state) throws IOException {
+    return new SimpleTextVectorWriter(state);
+  }
+
+  @Override
+  public VectorReader fieldsReader(SegmentReadState state) throws IOException {
+    return new SimpleTextVectorReader(state);
+  }
+
+  /** Extension of points data file */
+  static final String VECTOR_EXTENSION = "vec";
+
+  /** Extension of points index file */
+  static final String META_EXTENSION = "gri";
+}

lucene/codecs/src/java/org/apache/lucene/codecs/simpletext/SimpleTextVectorReader.java

@@ -0,0 +1,304 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.codecs.simpletext;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.charset.StandardCharsets;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.apache.lucene.codecs.VectorReader;
+import org.apache.lucene.index.CorruptIndexException;
+import org.apache.lucene.index.FieldInfo;
+import org.apache.lucene.index.IndexFileNames;
+import org.apache.lucene.index.SegmentReadState;
+import org.apache.lucene.index.VectorValues;
+import org.apache.lucene.search.TopDocs;
+import org.apache.lucene.store.BufferedChecksumIndexInput;
+import org.apache.lucene.store.ChecksumIndexInput;
+import org.apache.lucene.store.IOContext;
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.BytesRefBuilder;
+import org.apache.lucene.util.StringHelper;
+
+import static org.apache.lucene.codecs.simpletext.SimpleTextVectorWriter.*;
+
+/**
+ * Reads vector values from a simple text format. All vectors are read up front and cached in RAM in order to support
+ * random access.
+ * <b>FOR RECREATIONAL USE ONLY</b>
+ * @lucene.experimental
+ */
+public class SimpleTextVectorReader extends VectorReader {
+
+  private static final BytesRef EMPTY = new BytesRef("");
+
+  private final SegmentReadState readState;
+  private final IndexInput dataIn;
+  private final BytesRefBuilder scratch = new BytesRefBuilder();
+  private final Map<String, FieldEntry> fieldEntries = new HashMap<>();
+
+  SimpleTextVectorReader(SegmentReadState readState) throws IOException {
+    this.readState = readState;
+    String metaFileName = IndexFileNames.segmentFileName(readState.segmentInfo.name, readState.segmentSuffix, SimpleTextVectorFormat.META_EXTENSION);
+    try (ChecksumIndexInput in = readState.directory.openChecksumInput(metaFileName, IOContext.DEFAULT)) {
+      int fieldNumber = readInt(in, FIELD_NUMBER);
+      while (fieldNumber != -1) {
+        String fieldName = readString(in, FIELD_NAME);
+        String scoreFunctionName = readString(in, SCORE_FUNCTION);
+        VectorValues.ScoreFunction scoreFunction = VectorValues.ScoreFunction.valueOf(scoreFunctionName);
+        long vectorDataOffset = readLong(in, VECTOR_DATA_OFFSET);
+        long vectorDataLength = readLong(in, VECTOR_DATA_LENGTH);
+        int dimension = readInt(in, VECTOR_DIMENSION);
+        int size = readInt(in, SIZE);
+        int[] docIds = new int[size];
+        for (int i = 0; i < size; i++) {
+          docIds[i] = readInt(in, EMPTY);
+        }
+        assert fieldEntries.containsKey(fieldName) == false;
+        fieldEntries.put(fieldName, new FieldEntry(dimension, scoreFunction, vectorDataOffset, vectorDataLength, docIds));
+        fieldNumber = readInt(in, FIELD_NUMBER);
+      }
+      SimpleTextUtil.checkFooter(in);
+    }
+
+    String vectorFileName = IndexFileNames.segmentFileName(readState.segmentInfo.name, readState.segmentSuffix, SimpleTextVectorFormat.VECTOR_EXTENSION);
+    dataIn = readState.directory.openInput(vectorFileName, IOContext.DEFAULT);
+  }
+
+  @Override
+  public VectorValues getVectorValues(String field) throws IOException {
+    FieldInfo info = readState.fieldInfos.fieldInfo(field);
+    if (info == null) {
+      throw new IllegalStateException("No vectors indexed for field=\"" + field + "\"");
+    }
+    int dimension = info.getVectorDimension();
+    if (dimension == 0) {
+      return VectorValues.EMPTY;
+    }
+    FieldEntry fieldEntry = fieldEntries.get(field);
+    if (fieldEntry == null) {
+      throw new IllegalStateException("No entry found for vector field=\"" + field + "\"");
+    }
+    if (dimension != fieldEntry.dimension) {
+      throw new IllegalStateException("Inconsistent vector dimension for field=\"" + field + "\"; " + dimension + " != " + fieldEntry.dimension);
+    }
+    IndexInput bytesSlice = dataIn.slice("vector-data", fieldEntry.vectorDataOffset, fieldEntry.vectorDataLength);
+    return new SimpleTextVectorValues(fieldEntry, bytesSlice);
+  }
+
+  @Override
+  public void checkIntegrity() throws IOException {
+    IndexInput clone = dataIn.clone();
+    clone.seek(0);
+
+    // checksum is fixed-width encoded with 20 bytes, plus 1 byte for newline (the space is included in SimpleTextUtil.CHECKSUM):
+    long footerStartPos = dataIn.length() - (SimpleTextUtil.CHECKSUM.length + 21);
+    ChecksumIndexInput input = new BufferedChecksumIndexInput(clone);
+    while (true) {
+      SimpleTextUtil.readLine(input, scratch);
+      if (input.getFilePointer() >= footerStartPos) {
+        // Make sure we landed at precisely the right location:
+        if (input.getFilePointer() != footerStartPos) {
+          throw new CorruptIndexException("SimpleText failure: footer does not start at expected position current=" + input.getFilePointer() + " vs expected=" + footerStartPos, input);
+        }
+        SimpleTextUtil.checkFooter(input);
+        break;
+      }
+    }
+  }
+
+  @Override
+  public long ramBytesUsed() {
+    return 0;
+  }
+
+  @Override
+  public void close() throws IOException {
+    dataIn.close();
+  }
+
+  private static class FieldEntry {
+
+    final int dimension;
+    final VectorValues.ScoreFunction scoreFunction;
+
+    final long vectorDataOffset;
+    final long vectorDataLength;
+    final int[] ordToDoc;
+
+    FieldEntry(int dimension, VectorValues.ScoreFunction scoreFunction,
+               long vectorDataOffset, long vectorDataLength, int[] ordToDoc) {
+      this.dimension = dimension;
+      this.scoreFunction = scoreFunction;
+      this.vectorDataOffset = vectorDataOffset;
+      this.vectorDataLength = vectorDataLength;
+      this.ordToDoc = ordToDoc;
+    }
+
+    int size() {
+      return ordToDoc.length;
+    }
+  }
+
+  private static class SimpleTextVectorValues extends VectorValues implements VectorValues.RandomAccess {
+
+    private final BytesRefBuilder scratch = new BytesRefBuilder();
+    private final FieldEntry entry;
+    private final IndexInput in;
+    private final BytesRef binaryValue;
+    private final float[][] values;
+
+    int curOrd;
+
+    SimpleTextVectorValues(FieldEntry entry, IndexInput in) throws IOException {
+      this.entry = entry;
+      this.in = in;
+      values = new float[entry.size()][entry.dimension];
+      binaryValue = new BytesRef(entry.dimension * Float.BYTES);
+      binaryValue.length = binaryValue.bytes.length;
+      curOrd = -1;
+      readAllVectors();
+    }
+
+    @Override
+    public int dimension() {
+      return entry.dimension;
+    }
+
+    @Override
+    public int size() {
+      return entry.size();
+    }
+
+    @Override
+    public ScoreFunction scoreFunction() {
+      return entry.scoreFunction;
+    }
+
+    @Override
+    public float[] vectorValue() {
+      return values[curOrd];
+    }
+
+    @Override
+    public BytesRef binaryValue() {
+      ByteBuffer.wrap(binaryValue.bytes).asFloatBuffer().get(values[curOrd]);
+      return binaryValue;
+    }
+
+    @Override
+    public RandomAccess randomAccess() {
+      return this;
+    }
+
+    @Override
+    public int docID() {
+      if (curOrd == -1) {
+        return -1;
+      }
+      return entry.ordToDoc[curOrd];
+    }
+
+    @Override
+    public int nextDoc() throws IOException {
+      if (++curOrd < entry.size()) {
+        return docID();
+      }
+      return NO_MORE_DOCS;
+    }
+
+    @Override
+    public int advance(int target) throws IOException {
+      return slowAdvance(target);
+    }
+
+    @Override
+    public long cost() {
+      return size();
+    }
+
+    private void readAllVectors() throws IOException {
+      for (int i = 0; i < values.length; i++) {
+        readVector(values[i]);
+      }
+    }
+
+    private void readVector(float[] value) throws IOException {
+      SimpleTextUtil.readLine(in, scratch);
+      // skip leading " [" and strip trailing "]"
+      String s = new BytesRef(scratch.bytes(), 2, scratch.length() - 3).utf8ToString();
+      String[] floatStrings = s.split(",");
+      assert floatStrings.length == value.length : " read " + s + " when expecting " + value.length + " floats";
+      for (int i = 0; i < floatStrings.length; i++) {
+        value[i] = Float.parseFloat(floatStrings[i]);
+      }
+    }
+
+    @Override
+    public float[] vectorValue(int targetOrd) throws IOException {
+      return values[targetOrd];
+    }
+
+    @Override
+    public BytesRef binaryValue(int targetOrd) throws IOException {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public TopDocs search(float[] target, int k, int fanout) throws IOException {
+      throw new UnsupportedOperationException();
+    }
+  }
+
+  private int readInt(IndexInput in, BytesRef field) throws IOException {
+    SimpleTextUtil.readLine(in, scratch);
+    return parseInt(field);
+  }
+
+  private long readLong(IndexInput in, BytesRef field) throws IOException {
+    SimpleTextUtil.readLine(in, scratch);
+    return parseLong(field);
+  }
+
+  private String readString(IndexInput in, BytesRef field) throws IOException {
+    SimpleTextUtil.readLine(in, scratch);
+    return stripPrefix(field);
+  }
+
+  private boolean startsWith(BytesRef prefix) {
+    return StringHelper.startsWith(scratch.get(), prefix);
+  }
+
+  private int parseInt(BytesRef prefix) {
+    assert startsWith(prefix);
+    return Integer.parseInt(stripPrefix(prefix));
+  }
+
+  private long parseLong(BytesRef prefix) {
+    assert startsWith(prefix);
+    return Long.parseLong(stripPrefix(prefix));
+  }
+
+  private String stripPrefix(BytesRef prefix) {
+    int prefixLen = prefix.length;
+    return new String(scratch.bytes(), prefixLen, scratch.length() - prefixLen, StandardCharsets.UTF_8);
+  }
+}

lucene/codecs/src/java/org/apache/lucene/codecs/simpletext/SimpleTextVectorWriter.java

@@ -0,0 +1,148 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.codecs.simpletext;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.apache.lucene.codecs.VectorWriter;
+import org.apache.lucene.index.FieldInfo;
+import org.apache.lucene.index.IndexFileNames;
+import org.apache.lucene.index.SegmentWriteState;
+import org.apache.lucene.index.VectorValues;
+import org.apache.lucene.store.IndexOutput;
+import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.BytesRefBuilder;
+import org.apache.lucene.util.IOUtils;
+
+import static org.apache.lucene.search.DocIdSetIterator.NO_MORE_DOCS;
+
+/**
+ * Writes vector-valued fields in a plain text format
+ */
+public class SimpleTextVectorWriter extends VectorWriter {
+
+  static final BytesRef FIELD_NUMBER = new BytesRef("field-number ");
+  static final BytesRef FIELD_NAME = new BytesRef("field-name ");
+  static final BytesRef SCORE_FUNCTION = new BytesRef("score-function ");
+  static final BytesRef VECTOR_DATA_OFFSET = new BytesRef("vector-data-offset ");
+  static final BytesRef VECTOR_DATA_LENGTH = new BytesRef("vector-data-length ");
+  static final BytesRef VECTOR_DIMENSION = new BytesRef("vector-dimension ");
+  static final BytesRef SIZE = new BytesRef("size ");
+
+  private final IndexOutput meta, vectorData;
+  private final BytesRefBuilder scratch = new BytesRefBuilder();
+
+  SimpleTextVectorWriter(SegmentWriteState state) throws IOException {
+    assert state.fieldInfos.hasVectorValues();
+
+    String metaFileName = IndexFileNames.segmentFileName(state.segmentInfo.name, state.segmentSuffix, SimpleTextVectorFormat.META_EXTENSION);
+    meta = state.directory.createOutput(metaFileName, state.context);
+
+    String vectorDataFileName = IndexFileNames.segmentFileName(state.segmentInfo.name, state.segmentSuffix, SimpleTextVectorFormat.VECTOR_EXTENSION);
+    vectorData = state.directory.createOutput(vectorDataFileName, state.context);
+  }
+
+  @Override
+  public void writeField(FieldInfo fieldInfo, VectorValues vectors) throws IOException {
+    long vectorDataOffset = vectorData.getFilePointer();
+    List<Integer> docIds = new ArrayList<>();
+    int docV, ord = 0;
+    for (docV = vectors.nextDoc(); docV != NO_MORE_DOCS; docV = vectors.nextDoc(), ord++) {
+      writeVectorValue(vectors);
+      docIds.add(docV);
+    }
+    long vectorDataLength = vectorData.getFilePointer() - vectorDataOffset;
+    writeMeta(fieldInfo, vectorDataOffset, vectorDataLength, docIds);
+  }
+
+  private void writeVectorValue(VectorValues vectors) throws IOException {
+    // write vector value
+    float[] value = vectors.vectorValue();
+    assert value.length == vectors.dimension();
+    write(vectorData, Arrays.toString(value));
+    newline(vectorData);
+  }
+
+  private void writeMeta(FieldInfo field, long vectorDataOffset, long vectorDataLength, List<Integer> docIds) throws IOException {
+    writeField(meta, FIELD_NUMBER, field.number);
+    writeField(meta, FIELD_NAME, field.name);
+    writeField(meta, SCORE_FUNCTION, field.getVectorScoreFunction().name());
+    writeField(meta, VECTOR_DATA_OFFSET, vectorDataOffset);
+    writeField(meta, VECTOR_DATA_LENGTH, vectorDataLength);
+    writeField(meta, VECTOR_DIMENSION, field.getVectorDimension());
+    writeField(meta, SIZE, docIds.size());
+    for (Integer docId : docIds) {
+      writeInt(meta, docId);
+      newline(meta);
+    }
+    writeField(meta, FIELD_NUMBER, -1);
+  }
+
+  @Override
+  public void finish() throws IOException {
+    SimpleTextUtil.writeChecksum(meta, scratch);
+    SimpleTextUtil.writeChecksum(vectorData, scratch);
+  }
+
+  @Override
+  public void close() throws IOException {
+    IOUtils.close(vectorData, meta);
+  }
+
+  private void writeField(IndexOutput out, BytesRef fieldName, int value) throws IOException {
+    write(out, fieldName);
+    writeInt(out, value);
+    newline(out);
+  }
+
+  private void writeField(IndexOutput out, BytesRef fieldName, long value) throws IOException {
+    write(out, fieldName);
+    writeLong(out, value);
+    newline(out);
+  }
+
+  private void writeField(IndexOutput out, BytesRef fieldName, String value) throws IOException {
+    write(out, fieldName);
+    write(out, value);
+    newline(out);
+  }
+
+  private void write(IndexOutput out, String s) throws IOException {
+    SimpleTextUtil.write(out, s, scratch);
+  }
+
+  private void writeInt(IndexOutput out, int x) throws IOException {
+    SimpleTextUtil.write(out, Integer.toString(x), scratch);
+  }
+
+  private void writeLong(IndexOutput out, long x) throws IOException {
+    SimpleTextUtil.write(out, Long.toString(x), scratch);
+  }
+
+  private void write(IndexOutput out, BytesRef b) throws IOException {
+    SimpleTextUtil.write(out, b);
+  }
+
+  private void newline(IndexOutput out) throws IOException {
+    SimpleTextUtil.writeNewline(out);
+  }
+
+}

lucene/codecs/src/test/org/apache/lucene/codecs/uniformsplit/TestBlockWriter.java

@@ -24,6 +24,7 @@ import org.apache.lucene.codecs.lucene84.MockTermStateFactory;
 import org.apache.lucene.index.DocValuesType;
 import org.apache.lucene.index.FieldInfo;
 import org.apache.lucene.index.IndexOptions;
+import org.apache.lucene.index.VectorValues;
 import org.apache.lucene.store.ByteBuffersDataOutput;
 import org.apache.lucene.store.ByteBuffersIndexOutput;
 import org.apache.lucene.util.BytesRef;
@@ -120,6 +121,8 @@ public class TestBlockWriter extends LuceneTestCase {
         0,
         0,
         0,
+        0,
+        VectorValues.ScoreFunction.NONE,
         true
     );
   }

lucene/codecs/src/test/org/apache/lucene/codecs/uniformsplit/sharedterms/TestSTBlockReader.java

@@ -42,6 +42,7 @@ import org.apache.lucene.index.ImpactsEnum;
 import org.apache.lucene.index.IndexOptions;
 import org.apache.lucene.index.PostingsEnum;
 import org.apache.lucene.index.SegmentReadState;
+import org.apache.lucene.index.VectorValues;
 import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.DataInput;
 import org.apache.lucene.store.Directory;
@@ -203,6 +204,8 @@ public class TestSTBlockReader extends LuceneTestCase {
         0,
         0,
         0,
+        0,
+        VectorValues.ScoreFunction.NONE,
         false
     );
   }

lucene/core/src/java/org/apache/lucene/codecs/Codec.java

@@ -56,8 +56,7 @@ public abstract class Codec implements NamedSPILoader.NamedSPI {
       return LOADER;
     }
     
-    // TODO: should we use this, or maybe a system property is better?
-    static Codec defaultCodec = LOADER.lookup("Lucene87");
+    static Codec defaultCodec = LOADER.lookup("Lucene90");
   }
 
   private final String name;
@@ -110,6 +109,9 @@ public abstract class Codec implements NamedSPILoader.NamedSPI {
 
   /** Encodes/decodes points index */
   public abstract PointsFormat pointsFormat();
+
+  /** Encodes/decodes numeric vector fields */
+  public abstract VectorFormat vectorFormat();
   
   /** looks up a codec by name */
   public static Codec forName(String name) {

lucene/core/src/java/org/apache/lucene/codecs/FilterCodec.java

@@ -108,4 +108,9 @@ public abstract class FilterCodec extends Codec {
   public PointsFormat pointsFormat() {
     return delegate.pointsFormat();
   }
+
+  @Override
+  public VectorFormat vectorFormat() {
+    return delegate.vectorFormat();
+  }
 }

lucene/core/src/java/org/apache/lucene/codecs/VectorFormat.java

@@ -0,0 +1,76 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.codecs;
+
+import java.io.IOException;
+
+import org.apache.lucene.index.SegmentReadState;
+import org.apache.lucene.index.SegmentWriteState;
+import org.apache.lucene.index.VectorValues;
+
+/**
+ * Encodes/decodes per-document vector and any associated indexing structures required to support nearest-neighbor search
+ */
+public abstract class VectorFormat {
+
+  /** Sole constructor */
+  protected VectorFormat() {}
+
+  /**
+   * Returns a {@link VectorWriter} to write the vectors to the index.
+   */
+  public abstract VectorWriter fieldsWriter(SegmentWriteState state) throws IOException;
+
+  /**
+   * Returns a {@link VectorReader} to read the vectors from the index.
+   */
+  public abstract VectorReader fieldsReader(SegmentReadState state) throws IOException;
+
+  /**
+   * EMPTY throws an exception when written. It acts as a sentinel indicating a Codec that does not support vectors.
+   */
+  public static final VectorFormat EMPTY = new VectorFormat() {
+    @Override
+    public VectorWriter fieldsWriter(SegmentWriteState state) {
+      throw new UnsupportedOperationException("Attempt to write EMPTY VectorValues: maybe you forgot to use codec=Lucene90");
+    }
+
+    @Override
+    public VectorReader fieldsReader(SegmentReadState state) {
+      return new VectorReader() {
+        @Override
+        public void checkIntegrity() {
+        }
+
+        @Override
+        public VectorValues getVectorValues(String field)  {
+          return VectorValues.EMPTY;
+        }
+
+        @Override
+        public void close() throws IOException {
+        }
+
+        @Override
+        public long ramBytesUsed() {
+          return 0;
+        }
+      };
+    }
+  };
+}

lucene/core/src/java/org/apache/lucene/codecs/VectorReader.java

@@ -0,0 +1,55 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.codecs;
+
+import java.io.Closeable;
+import java.io.IOException;
+
+import org.apache.lucene.index.VectorValues;
+import org.apache.lucene.util.Accountable;
+
+/**
+ * Reads vectors from an index.
+ */
+public abstract class VectorReader implements Closeable, Accountable {
+
+  /** Sole constructor */
+  protected VectorReader() {}
+
+  /**
+   * Checks consistency of this reader.
+   * <p>
+   * Note that this may be costly in terms of I/O, e.g.
+   * may involve computing a checksum value against large data files.
+   * @lucene.internal
+   */
+  public abstract void checkIntegrity() throws IOException;
+
+  /** Returns the {@link VectorValues} for the given {@code field} */
+  public abstract VectorValues getVectorValues(String field) throws IOException;
+
+  /**
+   * Returns an instance optimized for merging. This instance may only be
+   * consumed in the thread that called {@link #getMergeInstance()}.
+   * <p>
+   * The default implementation returns {@code this} */
+  public VectorReader getMergeInstance() {
+    return this;
+  }
+
+}

lucene/core/src/java/org/apache/lucene/codecs/VectorWriter.java

@@ -0,0 +1,283 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.codecs;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.apache.lucene.index.DocIDMerger;
+import org.apache.lucene.index.FieldInfo;
+import org.apache.lucene.index.MergeState;
+import org.apache.lucene.index.VectorValues;
+import org.apache.lucene.search.TopDocs;
+import org.apache.lucene.util.BytesRef;
+
+import static org.apache.lucene.search.DocIdSetIterator.NO_MORE_DOCS;
+
+/**
+ * Writes vectors to an index.
+ */
+public abstract class VectorWriter implements Closeable {
+
+  /** Sole constructor */
+  protected VectorWriter() {}
+
+  /** Write all values contained in the provided reader */
+  public abstract void writeField(FieldInfo fieldInfo, VectorValues values) throws IOException;
+
+  /** Called once at the end before close */
+  public abstract void finish() throws IOException;
+
+  /** Merge the vector values from multiple segments, for all fields */
+  public void merge(MergeState mergeState) throws IOException {
+    for (int i = 0; i < mergeState.fieldInfos.length; i++) {
+      VectorReader reader = mergeState.vectorReaders[i];
+      assert reader != null || mergeState.fieldInfos[i].hasVectorValues() == false;
+      if (reader != null) {
+        reader.checkIntegrity();
+      }
+    }
+    for (FieldInfo fieldInfo : mergeState.mergeFieldInfos) {
+      if (fieldInfo.hasVectorValues()) {
+        mergeVectors(fieldInfo, mergeState);
+      }
+    }
+    finish();
+  }
+
+  private void mergeVectors(FieldInfo mergeFieldInfo, final MergeState mergeState) throws IOException {
+    if (mergeState.infoStream.isEnabled("VV")) {
+      mergeState.infoStream.message("VV", "merging " + mergeState.segmentInfo);
+    }
+    List<VectorValuesSub> subs = new ArrayList<>();
+    int dimension = -1;
+    VectorValues.ScoreFunction scoreFunction = null;
+    int nonEmptySegmentIndex = 0;
+    for (int i = 0; i < mergeState.vectorReaders.length; i++) {
+      VectorReader vectorReader = mergeState.vectorReaders[i];
+      if (vectorReader != null) {
+        if (mergeFieldInfo != null && mergeFieldInfo.hasVectorValues()) {
+          int segmentDimension = mergeFieldInfo.getVectorDimension();
+          VectorValues.ScoreFunction segmentScoreFunction = mergeFieldInfo.getVectorScoreFunction();
+          if (dimension == -1) {
+            dimension = segmentDimension;
+            scoreFunction = mergeFieldInfo.getVectorScoreFunction();
+          } else if (dimension != segmentDimension) {
+            throw new IllegalStateException("Varying dimensions for vector-valued field " + mergeFieldInfo.name
+                + ": " + dimension + "!=" + segmentDimension);
+          } else if (scoreFunction != segmentScoreFunction) {
+            throw new IllegalStateException("Varying score functions for vector-valued field " + mergeFieldInfo.name
+                + ": " + scoreFunction + "!=" + segmentScoreFunction);
+          }
+          VectorValues values = vectorReader.getVectorValues(mergeFieldInfo.name);
+          if (values != null) {
+            subs.add(new VectorValuesSub(nonEmptySegmentIndex++, mergeState.docMaps[i], values));
+          }
+        }
+      }
+    }
+    // Create a new VectorValues by iterating over the sub vectors, mapping the resulting
+    // docids using docMaps in the mergeState.
+    if (subs.size() > 0) {
+      writeField(mergeFieldInfo, new VectorValuesMerger(subs, mergeState));
+    }
+    if (mergeState.infoStream.isEnabled("VV")) {
+      mergeState.infoStream.message("VV", "merge done " + mergeState.segmentInfo);
+    }
+  }
+
+  /** Tracks state of one sub-reader that we are merging */
+  private static class VectorValuesSub extends DocIDMerger.Sub {
+
+    final MergeState.DocMap docMap;
+    final VectorValues values;
+    final int segmentIndex;
+    int count;
+
+    VectorValuesSub(int segmentIndex, MergeState.DocMap docMap, VectorValues values) {
+      super(docMap);
+      this.values = values;
+      this.segmentIndex = segmentIndex;
+      this.docMap = docMap;
+      assert values.docID() == -1;
+    }
+
+    @Override
+    public int nextDoc() throws IOException {
+      int docId = values.nextDoc();
+      if (docId != NO_MORE_DOCS) {
+        // Note: this does count deleted docs since they are present in the to-be-merged segment
+        ++count;
+      }
+      return docId;
+    }
+  }
+
+  /**
+   * View over multiple VectorValues supporting iterator-style access via DocIdMerger. Maintains a reverse ordinal
+   * mapping for documents having values in order to support random access by dense ordinal.
+   */
+  private static class VectorValuesMerger extends VectorValues {
+    private final List<VectorValuesSub> subs;
+    private final DocIDMerger<VectorValuesSub> docIdMerger;
+    private final int[] ordBase;
+    private final int cost;
+    private final int size;
+
+    private int docId;
+    private VectorValuesSub current;
+    // For each doc with a vector, record its ord in the segments being merged. This enables random access into the
+    // unmerged segments using the ords from the merged segment.
+    private int[] ordMap;
+    private int ord;
+
+    VectorValuesMerger(List<VectorValuesSub> subs, MergeState mergeState) throws IOException {
+      this.subs = subs;
+      docIdMerger = DocIDMerger.of(subs, mergeState.needsIndexSort);
+      int totalCost = 0, totalSize = 0;
+      for (VectorValuesSub sub : subs) {
+        totalCost += sub.values.cost();
+        totalSize += sub.values.size();
+      }
+      cost = totalCost;
+      size = totalSize;
+      ordMap = new int[size];
+      ordBase = new int[subs.size()];
+      int lastBase = 0;
+      for (int k = 0; k < subs.size(); k++) {
+        int size = subs.get(k).values.size();
+        ordBase[k] = lastBase;
+        lastBase += size;
+      }
+      docId = -1;
+    }
+
+    @Override
+    public int docID() {
+      return docId;
+    }
+
+    @Override
+    public int nextDoc() throws IOException {
+      current = docIdMerger.next();
+      if (current == null) {
+        docId = NO_MORE_DOCS;
+      } else {
+        docId = current.mappedDocID;
+        ordMap[ord++] = ordBase[current.segmentIndex] + current.count - 1;
+      }
+      return docId;
+    }
+
+    @Override
+    public float[] vectorValue() throws IOException {
+      return current.values.vectorValue();
+    }
+
+    @Override
+    public BytesRef binaryValue() throws IOException {
+      return current.values.binaryValue();
+    }
+
+    @Override
+    public RandomAccess randomAccess() {
+      return new MergerRandomAccess();
+    }
+
+    @Override
+    public int advance(int target) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public int size() {
+      return size;
+    }
+
+    @Override
+    public long cost() {
+      return cost;
+    }
+
+    @Override
+    public int dimension() {
+      return subs.get(0).values.dimension();
+    }
+
+    @Override
+    public VectorValues.ScoreFunction scoreFunction() {
+      return subs.get(0).values.scoreFunction();
+    }
+
+    class MergerRandomAccess implements VectorValues.RandomAccess {
+
+      private final List<RandomAccess> raSubs;
+
+      MergerRandomAccess() {
+        raSubs = new ArrayList<>(subs.size());
+        for (VectorValuesSub sub : subs) {
+          raSubs.add(sub.values.randomAccess());
+        }
+      }
+
+      @Override
+      public int size() {
+        return size;
+      }
+
+      @Override
+      public int dimension() {
+        return VectorValuesMerger.this.dimension();
+      }
+
+      @Override
+      public ScoreFunction scoreFunction() {
+        return VectorValuesMerger.this.scoreFunction();
+      }
+
+      @Override
+      public float[] vectorValue(int target) throws IOException {
+        int unmappedOrd = ordMap[target];
+        int segmentOrd = Arrays.binarySearch(ordBase, unmappedOrd);
+        if (segmentOrd < 0) {
+          // get the index of the greatest lower bound
+          segmentOrd = -2 - segmentOrd;
+        }
+        while(segmentOrd < ordBase.length - 1 && ordBase[segmentOrd + 1] == ordBase[segmentOrd]) {
+          // forward over empty segments which will share the same ordBase
+          segmentOrd++;
+        }
+        return raSubs.get(segmentOrd).vectorValue(unmappedOrd - ordBase[segmentOrd]);
+      }
+
+      @Override
+      public BytesRef binaryValue(int targetOrd) throws IOException {
+        throw new UnsupportedOperationException();
+      }
+
+      @Override
+      public TopDocs search(float[] target, int k, int fanout) throws IOException {
+        throw new UnsupportedOperationException();
+      }
+
+    }
+  }
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene50/Lucene50FieldInfosFormat.java

@@ -31,6 +31,7 @@ import org.apache.lucene.index.FieldInfos;
 import org.apache.lucene.index.IndexFileNames;
 import org.apache.lucene.index.IndexOptions;
 import org.apache.lucene.index.SegmentInfo;
+import org.apache.lucene.index.VectorValues;
 import org.apache.lucene.store.ChecksumIndexInput;
 import org.apache.lucene.store.DataOutput;
 import org.apache.lucene.store.Directory;
@@ -148,7 +149,8 @@ public final class Lucene50FieldInfosFormat extends FieldInfosFormat {
           lastAttributes = attributes;
           try {
             infos[i] = new FieldInfo(name, fieldNumber, storeTermVector, omitNorms, storePayloads, 
-                                     indexOptions, docValuesType, dvGen, attributes, 0, 0, 0, false);
+                                     indexOptions, docValuesType, dvGen, attributes, 0, 0, 0,
+                                     0, VectorValues.ScoreFunction.NONE, false);
           } catch (IllegalStateException e) {
             throw new CorruptIndexException("invalid fieldinfo for field: " + name + ", fieldNumber=" + fieldNumber, input, e);
           }

lucene/core/src/java/org/apache/lucene/codecs/lucene50/package-info.java

@@ -17,7 +17,7 @@
 
 /**
  * Components from the Lucene 5.0 index format
- * See {@link org.apache.lucene.codecs.lucene80} for an overview
+ * See {@link org.apache.lucene.codecs.lucene90} for an overview
  * of the index format.
  */
 package org.apache.lucene.codecs.lucene50;

lucene/core/src/java/org/apache/lucene/codecs/lucene60/Lucene60FieldInfosFormat.java

@@ -31,6 +31,7 @@ import org.apache.lucene.index.FieldInfos;
 import org.apache.lucene.index.IndexFileNames;
 import org.apache.lucene.index.IndexOptions;
 import org.apache.lucene.index.SegmentInfo;
+import org.apache.lucene.index.VectorValues;
 import org.apache.lucene.store.ChecksumIndexInput;
 import org.apache.lucene.store.DataOutput;
 import org.apache.lucene.store.Directory;
@@ -164,7 +165,8 @@ public final class Lucene60FieldInfosFormat extends FieldInfosFormat {
           try {
             infos[i] = new FieldInfo(name, fieldNumber, storeTermVector, omitNorms, storePayloads, 
                                      indexOptions, docValuesType, dvGen, attributes,
-                                     pointDataDimensionCount, pointIndexDimensionCount, pointNumBytes, isSoftDeletesField);
+                                     pointDataDimensionCount, pointIndexDimensionCount, pointNumBytes,
+                                     0, VectorValues.ScoreFunction.NONE, isSoftDeletesField);
           } catch (IllegalStateException e) {
             throw new CorruptIndexException("invalid fieldinfo for field: " + name + ", fieldNumber=" + fieldNumber, input, e);
           }

lucene/core/src/java/org/apache/lucene/codecs/lucene60/package-info.java

@@ -16,7 +16,7 @@
  */
 
 /**
- * Components from the Lucene 6.0 index format.  See {@link org.apache.lucene.codecs.lucene86}
+ * Components from the Lucene 6.0 index format.  See {@link org.apache.lucene.codecs.lucene90}
  * for an overview of the current index format.
  */
 package org.apache.lucene.codecs.lucene60;

lucene/core/src/java/org/apache/lucene/codecs/lucene80/package-info.java

@@ -17,7 +17,7 @@
 
 /**
  * Components from the Lucene 8.0 index format
- * See {@link org.apache.lucene.codecs.lucene84} for an overview
+ * See {@link org.apache.lucene.codecs.lucene90} for an overview
  * of the index format.
  */
 package org.apache.lucene.codecs.lucene80;

lucene/core/src/java/org/apache/lucene/codecs/lucene84/package-info.java

@@ -16,7 +16,7 @@
  */
 
 /**
- * Components from the Lucene 8.4 index format.  See {@link org.apache.lucene.codecs.lucene86}
+ * Components from the Lucene 8.4 index format.  See {@link org.apache.lucene.codecs.lucene90}
  * for an overview of the current index format.
  */
 package org.apache.lucene.codecs.lucene84;

lucene/core/src/java/org/apache/lucene/codecs/lucene86/package-info.java

@@ -16,401 +16,7 @@
  */
 
 /**
- * Lucene 8.6 file format.
- *
- * <h2>Apache Lucene - Index File Formats</h2>
- * <div>
- * <ul>
- * <li><a href="#Introduction">Introduction</a></li>
- * <li><a href="#Definitions">Definitions</a>
- *   <ul>
- *   <li><a href="#Inverted_Indexing">Inverted Indexing</a></li>
- *   <li><a href="#Types_of_Fields">Types of Fields</a></li>
- *   <li><a href="#Segments">Segments</a></li>
- *   <li><a href="#Document_Numbers">Document Numbers</a></li>
- *   </ul>
- * </li>
- * <li><a href="#Overview">Index Structure Overview</a></li>
- * <li><a href="#File_Naming">File Naming</a></li>
- * <li><a href="#file-names">Summary of File Extensions</a>
- *   <ul>
- *   <li><a href="#Lock_File">Lock File</a></li>
- *   <li><a href="#History">History</a></li>
- *   <li><a href="#Limitations">Limitations</a></li>
- *   </ul>
- * </li>
- * </ul>
- * </div>
- * <a id="Introduction"></a>
- * <h3>Introduction</h3>
- * <div>
- * <p>This document defines the index file formats used in this version of Lucene.
- * If you are using a different version of Lucene, please consult the copy of
- * <code>docs/</code> that was distributed with
- * the version you are using.</p>
- * <p>This document attempts to provide a high-level definition of the Apache
- * Lucene file formats.</p>
- * </div>
- * <a id="Definitions"></a>
- * <h3>Definitions</h3>
- * <div>
- * <p>The fundamental concepts in Lucene are index, document, field and term.</p>
- * <p>An index contains a sequence of documents.</p>
- * <ul>
- * <li>A document is a sequence of fields.</li>
- * <li>A field is a named sequence of terms.</li>
- * <li>A term is a sequence of bytes.</li>
- * </ul>
- * <p>The same sequence of bytes in two different fields is considered a different
- * term. Thus terms are represented as a pair: the string naming the field, and the
- * bytes within the field.</p>
- * <a id="Inverted_Indexing"></a>
- * <h4>Inverted Indexing</h4>
- * <p>The index stores statistics about terms in order to make term-based search
- * more efficient. Lucene's index falls into the family of indexes known as an
- * <i>inverted index.</i> This is because it can list, for a term, the documents
- * that contain it. This is the inverse of the natural relationship, in which
- * documents list terms.</p>
- * <a id="Types_of_Fields"></a>
- * <h4>Types of Fields</h4>
- * <p>In Lucene, fields may be <i>stored</i>, in which case their text is stored
- * in the index literally, in a non-inverted manner. Fields that are inverted are
- * called <i>indexed</i>. A field may be both stored and indexed.</p>
- * <p>The text of a field may be <i>tokenized</i> into terms to be indexed, or the
- * text of a field may be used literally as a term to be indexed. Most fields are
- * tokenized, but sometimes it is useful for certain identifier fields to be
- * indexed literally.</p>
- * <p>See the {@link org.apache.lucene.document.Field Field}
- * java docs for more information on Fields.</p>
- * <a id="Segments"></a>
- * <h4>Segments</h4>
- * <p>Lucene indexes may be composed of multiple sub-indexes, or <i>segments</i>.
- * Each segment is a fully independent index, which could be searched separately.
- * Indexes evolve by:</p>
- * <ol>
- * <li>Creating new segments for newly added documents.</li>
- * <li>Merging existing segments.</li>
- * </ol>
- * <p>Searches may involve multiple segments and/or multiple indexes, each index
- * potentially composed of a set of segments.</p>
- * <a id="Document_Numbers"></a>
- * <h4>Document Numbers</h4>
- * <p>Internally, Lucene refers to documents by an integer <i>document number</i>.
- * The first document added to an index is numbered zero, and each subsequent
- * document added gets a number one greater than the previous.</p>
- * <p>Note that a document's number may change, so caution should be taken when
- * storing these numbers outside of Lucene. In particular, numbers may change in
- * the following situations:</p>
- * <ul>
- * <li>
- * <p>The numbers stored in each segment are unique only within the segment, and
- * must be converted before they can be used in a larger context. The standard
- * technique is to allocate each segment a range of values, based on the range of
- * numbers used in that segment. To convert a document number from a segment to an
- * external value, the segment's <i>base</i> document number is added. To convert
- * an external value back to a segment-specific value, the segment is identified
- * by the range that the external value is in, and the segment's base value is
- * subtracted. For example two five document segments might be combined, so that
- * the first segment has a base value of zero, and the second of five. Document
- * three from the second segment would have an external value of eight.</p>
- * </li>
- * <li>
- * <p>When documents are deleted, gaps are created in the numbering. These are
- * eventually removed as the index evolves through merging. Deleted documents are
- * dropped when segments are merged. A freshly-merged segment thus has no gaps in
- * its numbering.</p>
- * </li>
- * </ul>
- * </div>
- * <a id="Overview"></a>
- * <h3>Index Structure Overview</h3>
- * <div>
- * <p>Each segment index maintains the following:</p>
- * <ul>
- * <li>
- * {@link org.apache.lucene.codecs.lucene86.Lucene86SegmentInfoFormat Segment info}.
- *    This contains metadata about a segment, such as the number of documents,
- *    what files it uses, and information about how the segment is sorted
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene60.Lucene60FieldInfosFormat Field names}.
- *    This contains the set of field names used in the index.
- * </li>
- * <li>
- * Stored Field values.
- * This contains, for each document, a list of attribute-value pairs, where the attributes
- * are field names. These are used to store auxiliary information about the document, such as
- * its title, url, or an identifier to access a database. The set of stored fields are what is
- * returned for each hit when searching. This is keyed by document number.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term dictionary}.
- * A dictionary containing all of the terms used in all of the
- * indexed fields of all of the documents. The dictionary also contains the number
- * of documents which contain the term, and pointers to the term's frequency and
- * proximity data.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term Frequency data}.
- * For each term in the dictionary, the numbers of all the
- * documents that contain that term, and the frequency of the term in that
- * document, unless frequencies are omitted ({@link org.apache.lucene.index.IndexOptions#DOCS IndexOptions.DOCS})
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term Proximity data}.
- * For each term in the dictionary, the positions that the
- * term occurs in each document. Note that this will not exist if all fields in
- * all documents omit position data.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene80.Lucene80NormsFormat Normalization factors}.
- * For each field in each document, a value is stored
- * that is multiplied into the score for hits on that field.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat Term Vectors}.
- * For each field in each document, the term vector (sometimes
- * called document vector) may be stored. A term vector consists of term text and
- * term frequency. To add Term Vectors to your index see the
- * {@link org.apache.lucene.document.Field Field} constructors
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat Per-document values}.
- * Like stored values, these are also keyed by document
- * number, but are generally intended to be loaded into main memory for fast
- * access. Whereas stored values are generally intended for summary results from
- * searches, per-document values are useful for things like scoring factors.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene50.Lucene50LiveDocsFormat Live documents}.
- * An optional file indicating which documents are live.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene86.Lucene86PointsFormat Point values}.
- * Optional pair of files, recording dimensionally indexed fields, to enable fast
- * numeric range filtering and large numeric values like BigInteger and BigDecimal (1D)
- * and geographic shape intersection (2D, 3D).
- * </li>
- * </ul>
- * <p>Details on each of these are provided in their linked pages.</p>
- * </div>
- * <a id="File_Naming"></a>
- * <h3>File Naming</h3>
- * <div>
- * <p>All files belonging to a segment have the same name with varying extensions.
- * The extensions correspond to the different file formats described below. When
- * using the Compound File format (default for small segments) these files (except
- * for the Segment info file, the Lock file, and Deleted documents file) are collapsed
- * into a single .cfs file (see below for details)</p>
- * <p>Typically, all segments in an index are stored in a single directory,
- * although this is not required.</p>
- * <p>File names are never re-used. That is, when any file is saved
- * to the Directory it is given a never before used filename. This is achieved
- * using a simple generations approach. For example, the first segments file is
- * segments_1, then segments_2, etc. The generation is a sequential long integer
- * represented in alpha-numeric (base 36) form.</p>
- * </div>
- * <a id="file-names"></a>
- * <h3>Summary of File Extensions</h3>
- * <div>
- * <p>The following table summarizes the names and extensions of the files in
- * Lucene:</p>
- * <table class="padding4" style="border-spacing: 1px; border-collapse: separate">
- * <caption>lucene filenames by extension</caption>
- * <tr>
- * <th>Name</th>
- * <th>Extension</th>
- * <th>Brief Description</th>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.index.SegmentInfos Segments File}</td>
- * <td>segments_N</td>
- * <td>Stores information about a commit point</td>
- * </tr>
- * <tr>
- * <td><a href="#Lock_File">Lock File</a></td>
- * <td>write.lock</td>
- * <td>The Write lock prevents multiple IndexWriters from writing to the same
- * file.</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene86.Lucene86SegmentInfoFormat Segment Info}</td>
- * <td>.si</td>
- * <td>Stores metadata about a segment</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50CompoundFormat Compound File}</td>
- * <td>.cfs, .cfe</td>
- * <td>An optional "virtual" file consisting of all the other index files for
- * systems that frequently run out of file handles.</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene60.Lucene60FieldInfosFormat Fields}</td>
- * <td>.fnm</td>
- * <td>Stores information about the fields</td>
- * </tr>
- * <tr>
- * <td>Field Index</td>
- * <td>.fdx</td>
- * <td>Contains pointers to field data</td>
- * </tr>
- * <tr>
- * <td>Field Data</td>
- * <td>.fdt</td>
- * <td>The stored fields for documents</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term Dictionary}</td>
- * <td>.tim</td>
- * <td>The term dictionary, stores term info</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term Index}</td>
- * <td>.tip</td>
- * <td>The index into the Term Dictionary</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Frequencies}</td>
- * <td>.doc</td>
- * <td>Contains the list of docs which contain each term along with frequency</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Positions}</td>
- * <td>.pos</td>
- * <td>Stores position information about where a term occurs in the index</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Payloads}</td>
- * <td>.pay</td>
- * <td>Stores additional per-position metadata information such as character offsets and user payloads</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene80.Lucene80NormsFormat Norms}</td>
- * <td>.nvd, .nvm</td>
- * <td>Encodes length and boost factors for docs and fields</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat Per-Document Values}</td>
- * <td>.dvd, .dvm</td>
- * <td>Encodes additional scoring factors or other per-document information.</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat Term Vector Index}</td>
- * <td>.tvx</td>
- * <td>Stores offset into the document data file</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat Term Vector Data}</td>
- * <td>.tvd</td>
- * <td>Contains term vector data.</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50LiveDocsFormat Live Documents}</td>
- * <td>.liv</td>
- * <td>Info about what documents are live</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene86.Lucene86PointsFormat Point values}</td>
- * <td>.dii, .dim</td>
- * <td>Holds indexed points, if any</td>
- * </tr>
- * </table>
- * </div>
- * <a id="Lock_File"></a>
- * <h3>Lock File</h3>
- * The write lock, which is stored in the index directory by default, is named
- * "write.lock". If the lock directory is different from the index directory then
- * the write lock will be named "XXXX-write.lock" where XXXX is a unique prefix
- * derived from the full path to the index directory. When this file is present, a
- * writer is currently modifying the index (adding or removing documents). This
- * lock file ensures that only one writer is modifying the index at a time.
- * <a id="History"></a>
- * <h3>History</h3>
- * <p>Compatibility notes are provided in this document, describing how file
- * formats have changed from prior versions:</p>
- * <ul>
- * <li>In version 2.1, the file format was changed to allow lock-less commits (ie,
- * no more commit lock). The change is fully backwards compatible: you can open a
- * pre-2.1 index for searching or adding/deleting of docs. When the new segments
- * file is saved (committed), it will be written in the new file format (meaning
- * no specific "upgrade" process is needed). But note that once a commit has
- * occurred, pre-2.1 Lucene will not be able to read the index.</li>
- * <li>In version 2.3, the file format was changed to allow segments to share a
- * single set of doc store (vectors &amp; stored fields) files. This allows for
- * faster indexing in certain cases. The change is fully backwards compatible (in
- * the same way as the lock-less commits change in 2.1).</li>
- * <li>In version 2.4, Strings are now written as true UTF-8 byte sequence, not
- * Java's modified UTF-8. See <a href="http://issues.apache.org/jira/browse/LUCENE-510">
- * LUCENE-510</a> for details.</li>
- * <li>In version 2.9, an optional opaque Map&lt;String,String&gt; CommitUserData
- * may be passed to IndexWriter's commit methods (and later retrieved), which is
- * recorded in the segments_N file. See <a href="http://issues.apache.org/jira/browse/LUCENE-1382">
- * LUCENE-1382</a> for details. Also,
- * diagnostics were added to each segment written recording details about why it
- * was written (due to flush, merge; which OS/JRE was used; etc.). See issue
- * <a href="http://issues.apache.org/jira/browse/LUCENE-1654">LUCENE-1654</a> for details.</li>
- * <li>In version 3.0, compressed fields are no longer written to the index (they
- * can still be read, but on merge the new segment will write them, uncompressed).
- * See issue <a href="http://issues.apache.org/jira/browse/LUCENE-1960">LUCENE-1960</a>
- * for details.</li>
- * <li>In version 3.1, segments records the code version that created them. See
- * <a href="http://issues.apache.org/jira/browse/LUCENE-2720">LUCENE-2720</a> for details.
- * Additionally segments track explicitly whether or not they have term vectors.
- * See <a href="http://issues.apache.org/jira/browse/LUCENE-2811">LUCENE-2811</a>
- * for details.</li>
- * <li>In version 3.2, numeric fields are written as natively to stored fields
- * file, previously they were stored in text format only.</li>
- * <li>In version 3.4, fields can omit position data while still indexing term
- * frequencies.</li>
- * <li>In version 4.0, the format of the inverted index became extensible via
- * the {@link org.apache.lucene.codecs.Codec Codec} api. Fast per-document storage
- * ({@code DocValues}) was introduced. Normalization factors need no longer be a
- * single byte, they can be any {@link org.apache.lucene.index.NumericDocValues NumericDocValues}.
- * Terms need not be unicode strings, they can be any byte sequence. Term offsets
- * can optionally be indexed into the postings lists. Payloads can be stored in the
- * term vectors.</li>
- * <li>In version 4.1, the format of the postings list changed to use either
- * of FOR compression or variable-byte encoding, depending upon the frequency
- * of the term. Terms appearing only once were changed to inline directly into
- * the term dictionary. Stored fields are compressed by default. </li>
- * <li>In version 4.2, term vectors are compressed by default. DocValues has
- * a new multi-valued type (SortedSet), that can be used for faceting/grouping/joining
- * on multi-valued fields.</li>
- * <li>In version 4.5, DocValues were extended to explicitly represent missing values.</li>
- * <li>In version 4.6, FieldInfos were extended to support per-field DocValues generation, to
- * allow updating NumericDocValues fields.</li>
- * <li>In version 4.8, checksum footers were added to the end of each index file
- * for improved data integrity. Specifically, the last 8 bytes of every index file
- * contain the zlib-crc32 checksum of the file.</li>
- * <li>In version 4.9, DocValues has a new multi-valued numeric type (SortedNumeric)
- * that is suitable for faceting/sorting/analytics.
- * <li>In version 5.4, DocValues have been improved to store more information on disk:
- * addresses for binary fields and ord indexes for multi-valued fields.
- * <li>In version 6.0, Points were added, for multi-dimensional range/distance search.
- * <li>In version 6.2, new Segment info format that reads/writes the index sort, to support index sorting.
- * <li>In version 7.0, DocValues have been improved to better support sparse doc values
- * thanks to an iterator API.</li>
- * <li>In version 8.0, postings have been enhanced to record, for each block of
- * doc ids, the (term freq, normalization factor) pairs that may trigger the
- * maximum score of the block. This information is recorded alongside skip data
- * in order to be able to skip blocks of doc ids if they may not produce high
- * enough scores.
- * Additionally doc values and norms has been extended with jump-tables to make access O(1)
- * instead of O(n), where n is the number of elements to skip when advancing in the data.</li>
- * <li>In version 8.4, postings, positions, offsets and payload lengths have move to a more
- * performant encoding that is vectorized.</li>
- * <li>In version 8.6, index sort serialization is delegated to the sorts themselves, to
- * allow user-defined sorts to be used</li>
- * </ul>
- * <a id="Limitations"></a>
- * <h3>Limitations</h3>
- * <div>
- * <p>Lucene uses a Java <code>int</code> to refer to
- * document numbers, and the index file format uses an <code>Int32</code>
- * on-disk to store document numbers. This is a limitation
- * of both the index file format and the current implementation. Eventually these
- * should be replaced with either <code>UInt64</code> values, or
- * better yet, {@link org.apache.lucene.store.DataOutput#writeVInt VInt} values which have no limit.</p>
- * </div>
+ * Components from the Lucene 8.6 index format.  See {@link org.apache.lucene.codecs.lucene90}
+ * for an overview of the current index format.
  */
 package org.apache.lucene.codecs.lucene86;

lucene/core/src/java/org/apache/lucene/codecs/lucene87/package-info.java

@@ -16,401 +16,7 @@
  */
 
 /**
- * Lucene 8.7 file format.
- *
- * <h2>Apache Lucene - Index File Formats</h2>
- * <div>
- * <ul>
- * <li><a href="#Introduction">Introduction</a></li>
- * <li><a href="#Definitions">Definitions</a>
- *   <ul>
- *   <li><a href="#Inverted_Indexing">Inverted Indexing</a></li>
- *   <li><a href="#Types_of_Fields">Types of Fields</a></li>
- *   <li><a href="#Segments">Segments</a></li>
- *   <li><a href="#Document_Numbers">Document Numbers</a></li>
- *   </ul>
- * </li>
- * <li><a href="#Overview">Index Structure Overview</a></li>
- * <li><a href="#File_Naming">File Naming</a></li>
- * <li><a href="#file-names">Summary of File Extensions</a>
- *   <ul>
- *   <li><a href="#Lock_File">Lock File</a></li>
- *   <li><a href="#History">History</a></li>
- *   <li><a href="#Limitations">Limitations</a></li>
- *   </ul>
- * </li>
- * </ul>
- * </div>
- * <a id="Introduction"></a>
- * <h3>Introduction</h3>
- * <div>
- * <p>This document defines the index file formats used in this version of Lucene.
- * If you are using a different version of Lucene, please consult the copy of
- * <code>docs/</code> that was distributed with
- * the version you are using.</p>
- * <p>This document attempts to provide a high-level definition of the Apache
- * Lucene file formats.</p>
- * </div>
- * <a id="Definitions"></a>
- * <h3>Definitions</h3>
- * <div>
- * <p>The fundamental concepts in Lucene are index, document, field and term.</p>
- * <p>An index contains a sequence of documents.</p>
- * <ul>
- * <li>A document is a sequence of fields.</li>
- * <li>A field is a named sequence of terms.</li>
- * <li>A term is a sequence of bytes.</li>
- * </ul>
- * <p>The same sequence of bytes in two different fields is considered a different
- * term. Thus terms are represented as a pair: the string naming the field, and the
- * bytes within the field.</p>
- * <a id="Inverted_Indexing"></a>
- * <h4>Inverted Indexing</h4>
- * <p>The index stores statistics about terms in order to make term-based search
- * more efficient. Lucene's index falls into the family of indexes known as an
- * <i>inverted index.</i> This is because it can list, for a term, the documents
- * that contain it. This is the inverse of the natural relationship, in which
- * documents list terms.</p>
- * <a id="Types_of_Fields"></a>
- * <h4>Types of Fields</h4>
- * <p>In Lucene, fields may be <i>stored</i>, in which case their text is stored
- * in the index literally, in a non-inverted manner. Fields that are inverted are
- * called <i>indexed</i>. A field may be both stored and indexed.</p>
- * <p>The text of a field may be <i>tokenized</i> into terms to be indexed, or the
- * text of a field may be used literally as a term to be indexed. Most fields are
- * tokenized, but sometimes it is useful for certain identifier fields to be
- * indexed literally.</p>
- * <p>See the {@link org.apache.lucene.document.Field Field}
- * java docs for more information on Fields.</p>
- * <a id="Segments"></a>
- * <h4>Segments</h4>
- * <p>Lucene indexes may be composed of multiple sub-indexes, or <i>segments</i>.
- * Each segment is a fully independent index, which could be searched separately.
- * Indexes evolve by:</p>
- * <ol>
- * <li>Creating new segments for newly added documents.</li>
- * <li>Merging existing segments.</li>
- * </ol>
- * <p>Searches may involve multiple segments and/or multiple indexes, each index
- * potentially composed of a set of segments.</p>
- * <a id="Document_Numbers"></a>
- * <h4>Document Numbers</h4>
- * <p>Internally, Lucene refers to documents by an integer <i>document number</i>.
- * The first document added to an index is numbered zero, and each subsequent
- * document added gets a number one greater than the previous.</p>
- * <p>Note that a document's number may change, so caution should be taken when
- * storing these numbers outside of Lucene. In particular, numbers may change in
- * the following situations:</p>
- * <ul>
- * <li>
- * <p>The numbers stored in each segment are unique only within the segment, and
- * must be converted before they can be used in a larger context. The standard
- * technique is to allocate each segment a range of values, based on the range of
- * numbers used in that segment. To convert a document number from a segment to an
- * external value, the segment's <i>base</i> document number is added. To convert
- * an external value back to a segment-specific value, the segment is identified
- * by the range that the external value is in, and the segment's base value is
- * subtracted. For example two five document segments might be combined, so that
- * the first segment has a base value of zero, and the second of five. Document
- * three from the second segment would have an external value of eight.</p>
- * </li>
- * <li>
- * <p>When documents are deleted, gaps are created in the numbering. These are
- * eventually removed as the index evolves through merging. Deleted documents are
- * dropped when segments are merged. A freshly-merged segment thus has no gaps in
- * its numbering.</p>
- * </li>
- * </ul>
- * </div>
- * <a id="Overview"></a>
- * <h3>Index Structure Overview</h3>
- * <div>
- * <p>Each segment index maintains the following:</p>
- * <ul>
- * <li>
- * {@link org.apache.lucene.codecs.lucene86.Lucene86SegmentInfoFormat Segment info}.
- *    This contains metadata about a segment, such as the number of documents,
- *    what files it uses, and information about how the segment is sorted
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene60.Lucene60FieldInfosFormat Field names}.
- *    This contains the set of field names used in the index.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat Stored Field values}.
- * This contains, for each document, a list of attribute-value pairs, where the attributes
- * are field names. These are used to store auxiliary information about the document, such as
- * its title, url, or an identifier to access a database. The set of stored fields are what is
- * returned for each hit when searching. This is keyed by document number.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term dictionary}.
- * A dictionary containing all of the terms used in all of the
- * indexed fields of all of the documents. The dictionary also contains the number
- * of documents which contain the term, and pointers to the term's frequency and
- * proximity data.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term Frequency data}.
- * For each term in the dictionary, the numbers of all the
- * documents that contain that term, and the frequency of the term in that
- * document, unless frequencies are omitted ({@link org.apache.lucene.index.IndexOptions#DOCS IndexOptions.DOCS})
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term Proximity data}.
- * For each term in the dictionary, the positions that the
- * term occurs in each document. Note that this will not exist if all fields in
- * all documents omit position data.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene80.Lucene80NormsFormat Normalization factors}.
- * For each field in each document, a value is stored
- * that is multiplied into the score for hits on that field.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat Term Vectors}.
- * For each field in each document, the term vector (sometimes
- * called document vector) may be stored. A term vector consists of term text and
- * term frequency. To add Term Vectors to your index see the
- * {@link org.apache.lucene.document.Field Field} constructors
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat Per-document values}.
- * Like stored values, these are also keyed by document
- * number, but are generally intended to be loaded into main memory for fast
- * access. Whereas stored values are generally intended for summary results from
- * searches, per-document values are useful for things like scoring factors.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene50.Lucene50LiveDocsFormat Live documents}.
- * An optional file indicating which documents are live.
- * </li>
- * <li>
- * {@link org.apache.lucene.codecs.lucene86.Lucene86PointsFormat Point values}.
- * Optional pair of files, recording dimensionally indexed fields, to enable fast
- * numeric range filtering and large numeric values like BigInteger and BigDecimal (1D)
- * and geographic shape intersection (2D, 3D).
- * </li>
- * </ul>
- * <p>Details on each of these are provided in their linked pages.</p>
- * </div>
- * <a id="File_Naming"></a>
- * <h3>File Naming</h3>
- * <div>
- * <p>All files belonging to a segment have the same name with varying extensions.
- * The extensions correspond to the different file formats described below. When
- * using the Compound File format (default for small segments) these files (except
- * for the Segment info file, the Lock file, and Deleted documents file) are collapsed
- * into a single .cfs file (see below for details)</p>
- * <p>Typically, all segments in an index are stored in a single directory,
- * although this is not required.</p>
- * <p>File names are never re-used. That is, when any file is saved
- * to the Directory it is given a never before used filename. This is achieved
- * using a simple generations approach. For example, the first segments file is
- * segments_1, then segments_2, etc. The generation is a sequential long integer
- * represented in alpha-numeric (base 36) form.</p>
- * </div>
- * <a id="file-names"></a>
- * <h3>Summary of File Extensions</h3>
- * <div>
- * <p>The following table summarizes the names and extensions of the files in
- * Lucene:</p>
- * <table class="padding4" style="border-spacing: 1px; border-collapse: separate">
- * <caption>lucene filenames by extension</caption>
- * <tr>
- * <th>Name</th>
- * <th>Extension</th>
- * <th>Brief Description</th>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.index.SegmentInfos Segments File}</td>
- * <td>segments_N</td>
- * <td>Stores information about a commit point</td>
- * </tr>
- * <tr>
- * <td><a href="#Lock_File">Lock File</a></td>
- * <td>write.lock</td>
- * <td>The Write lock prevents multiple IndexWriters from writing to the same
- * file.</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene86.Lucene86SegmentInfoFormat Segment Info}</td>
- * <td>.si</td>
- * <td>Stores metadata about a segment</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50CompoundFormat Compound File}</td>
- * <td>.cfs, .cfe</td>
- * <td>An optional "virtual" file consisting of all the other index files for
- * systems that frequently run out of file handles.</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene60.Lucene60FieldInfosFormat Fields}</td>
- * <td>.fnm</td>
- * <td>Stores information about the fields</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat Field Index}</td>
- * <td>.fdx</td>
- * <td>Contains pointers to field data</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat Field Data}</td>
- * <td>.fdt</td>
- * <td>The stored fields for documents</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term Dictionary}</td>
- * <td>.tim</td>
- * <td>The term dictionary, stores term info</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term Index}</td>
- * <td>.tip</td>
- * <td>The index into the Term Dictionary</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Frequencies}</td>
- * <td>.doc</td>
- * <td>Contains the list of docs which contain each term along with frequency</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Positions}</td>
- * <td>.pos</td>
- * <td>Stores position information about where a term occurs in the index</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Payloads}</td>
- * <td>.pay</td>
- * <td>Stores additional per-position metadata information such as character offsets and user payloads</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene80.Lucene80NormsFormat Norms}</td>
- * <td>.nvd, .nvm</td>
- * <td>Encodes length and boost factors for docs and fields</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat Per-Document Values}</td>
- * <td>.dvd, .dvm</td>
- * <td>Encodes additional scoring factors or other per-document information.</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat Term Vector Index}</td>
- * <td>.tvx</td>
- * <td>Stores offset into the document data file</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat Term Vector Data}</td>
- * <td>.tvd</td>
- * <td>Contains term vector data.</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50LiveDocsFormat Live Documents}</td>
- * <td>.liv</td>
- * <td>Info about what documents are live</td>
- * </tr>
- * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene86.Lucene86PointsFormat Point values}</td>
- * <td>.dii, .dim</td>
- * <td>Holds indexed points, if any</td>
- * </tr>
- * </table>
- * </div>
- * <a id="Lock_File"></a>
- * <h3>Lock File</h3>
- * The write lock, which is stored in the index directory by default, is named
- * "write.lock". If the lock directory is different from the index directory then
- * the write lock will be named "XXXX-write.lock" where XXXX is a unique prefix
- * derived from the full path to the index directory. When this file is present, a
- * writer is currently modifying the index (adding or removing documents). This
- * lock file ensures that only one writer is modifying the index at a time.
- * <a id="History"></a>
- * <h3>History</h3>
- * <p>Compatibility notes are provided in this document, describing how file
- * formats have changed from prior versions:</p>
- * <ul>
- * <li>In version 2.1, the file format was changed to allow lock-less commits (ie,
- * no more commit lock). The change is fully backwards compatible: you can open a
- * pre-2.1 index for searching or adding/deleting of docs. When the new segments
- * file is saved (committed), it will be written in the new file format (meaning
- * no specific "upgrade" process is needed). But note that once a commit has
- * occurred, pre-2.1 Lucene will not be able to read the index.</li>
- * <li>In version 2.3, the file format was changed to allow segments to share a
- * single set of doc store (vectors &amp; stored fields) files. This allows for
- * faster indexing in certain cases. The change is fully backwards compatible (in
- * the same way as the lock-less commits change in 2.1).</li>
- * <li>In version 2.4, Strings are now written as true UTF-8 byte sequence, not
- * Java's modified UTF-8. See <a href="http://issues.apache.org/jira/browse/LUCENE-510">
- * LUCENE-510</a> for details.</li>
- * <li>In version 2.9, an optional opaque Map&lt;String,String&gt; CommitUserData
- * may be passed to IndexWriter's commit methods (and later retrieved), which is
- * recorded in the segments_N file. See <a href="http://issues.apache.org/jira/browse/LUCENE-1382">
- * LUCENE-1382</a> for details. Also,
- * diagnostics were added to each segment written recording details about why it
- * was written (due to flush, merge; which OS/JRE was used; etc.). See issue
- * <a href="http://issues.apache.org/jira/browse/LUCENE-1654">LUCENE-1654</a> for details.</li>
- * <li>In version 3.0, compressed fields are no longer written to the index (they
- * can still be read, but on merge the new segment will write them, uncompressed).
- * See issue <a href="http://issues.apache.org/jira/browse/LUCENE-1960">LUCENE-1960</a>
- * for details.</li>
- * <li>In version 3.1, segments records the code version that created them. See
- * <a href="http://issues.apache.org/jira/browse/LUCENE-2720">LUCENE-2720</a> for details.
- * Additionally segments track explicitly whether or not they have term vectors.
- * See <a href="http://issues.apache.org/jira/browse/LUCENE-2811">LUCENE-2811</a>
- * for details.</li>
- * <li>In version 3.2, numeric fields are written as natively to stored fields
- * file, previously they were stored in text format only.</li>
- * <li>In version 3.4, fields can omit position data while still indexing term
- * frequencies.</li>
- * <li>In version 4.0, the format of the inverted index became extensible via
- * the {@link org.apache.lucene.codecs.Codec Codec} api. Fast per-document storage
- * ({@code DocValues}) was introduced. Normalization factors need no longer be a
- * single byte, they can be any {@link org.apache.lucene.index.NumericDocValues NumericDocValues}.
- * Terms need not be unicode strings, they can be any byte sequence. Term offsets
- * can optionally be indexed into the postings lists. Payloads can be stored in the
- * term vectors.</li>
- * <li>In version 4.1, the format of the postings list changed to use either
- * of FOR compression or variable-byte encoding, depending upon the frequency
- * of the term. Terms appearing only once were changed to inline directly into
- * the term dictionary. Stored fields are compressed by default. </li>
- * <li>In version 4.2, term vectors are compressed by default. DocValues has
- * a new multi-valued type (SortedSet), that can be used for faceting/grouping/joining
- * on multi-valued fields.</li>
- * <li>In version 4.5, DocValues were extended to explicitly represent missing values.</li>
- * <li>In version 4.6, FieldInfos were extended to support per-field DocValues generation, to
- * allow updating NumericDocValues fields.</li>
- * <li>In version 4.8, checksum footers were added to the end of each index file
- * for improved data integrity. Specifically, the last 8 bytes of every index file
- * contain the zlib-crc32 checksum of the file.</li>
- * <li>In version 4.9, DocValues has a new multi-valued numeric type (SortedNumeric)
- * that is suitable for faceting/sorting/analytics.
- * <li>In version 5.4, DocValues have been improved to store more information on disk:
- * addresses for binary fields and ord indexes for multi-valued fields.
- * <li>In version 6.0, Points were added, for multi-dimensional range/distance search.
- * <li>In version 6.2, new Segment info format that reads/writes the index sort, to support index sorting.
- * <li>In version 7.0, DocValues have been improved to better support sparse doc values
- * thanks to an iterator API.</li>
- * <li>In version 8.0, postings have been enhanced to record, for each block of
- * doc ids, the (term freq, normalization factor) pairs that may trigger the
- * maximum score of the block. This information is recorded alongside skip data
- * in order to be able to skip blocks of doc ids if they may not produce high
- * enough scores.
- * Additionally doc values and norms has been extended with jump-tables to make access O(1)
- * instead of O(n), where n is the number of elements to skip when advancing in the data.</li>
- * <li>In version 8.4, postings, positions, offsets and payload lengths have move to a more
- * performant encoding that is vectorized.</li>
- * <li>In version 8.6, index sort serialization is delegated to the sorts themselves, to
- * allow user-defined sorts to be used</li>
- * </ul>
- * <a id="Limitations"></a>
- * <h3>Limitations</h3>
- * <div>
- * <p>Lucene uses a Java <code>int</code> to refer to
- * document numbers, and the index file format uses an <code>Int32</code>
- * on-disk to store document numbers. This is a limitation
- * of both the index file format and the current implementation. Eventually these
- * should be replaced with either <code>UInt64</code> values, or
- * better yet, {@link org.apache.lucene.store.DataOutput#writeVInt VInt} values which have no limit.</p>
- * </div>
+ * Components from the Lucene 8.7 index format.  See {@link org.apache.lucene.codecs.lucene90}
+ * for an overview of the current index format.
  */
 package org.apache.lucene.codecs.lucene87;

lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90Codec.java

@@ -0,0 +1,183 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.codecs.lucene90;
+
+import java.util.Objects;
+
+import org.apache.lucene.codecs.Codec;
+import org.apache.lucene.codecs.CompoundFormat;
+import org.apache.lucene.codecs.DocValuesFormat;
+import org.apache.lucene.codecs.FieldInfosFormat;
+import org.apache.lucene.codecs.FilterCodec;
+import org.apache.lucene.codecs.VectorFormat;
+import org.apache.lucene.codecs.LiveDocsFormat;
+import org.apache.lucene.codecs.NormsFormat;
+import org.apache.lucene.codecs.PointsFormat;
+import org.apache.lucene.codecs.PostingsFormat;
+import org.apache.lucene.codecs.SegmentInfoFormat;
+import org.apache.lucene.codecs.StoredFieldsFormat;
+import org.apache.lucene.codecs.TermVectorsFormat;
+import org.apache.lucene.codecs.lucene50.Lucene50CompoundFormat;
+import org.apache.lucene.codecs.lucene50.Lucene50LiveDocsFormat;
+import org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat;
+import org.apache.lucene.codecs.lucene80.Lucene80NormsFormat;
+import org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat;
+import org.apache.lucene.codecs.lucene86.Lucene86PointsFormat;
+import org.apache.lucene.codecs.lucene86.Lucene86SegmentInfoFormat;
+import org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat;
+import org.apache.lucene.codecs.perfield.PerFieldDocValuesFormat;
+import org.apache.lucene.codecs.perfield.PerFieldPostingsFormat;
+
+/**
+ * Implements the Lucene 9.0 index format
+ * <p>
+ * If you want to reuse functionality of this codec in another codec, extend
+ * {@link FilterCodec}.
+ *
+ * @see org.apache.lucene.codecs.lucene90 package documentation for file format details.
+ *
+ * @lucene.experimental
+ */
+public class Lucene90Codec extends Codec {
+  private final TermVectorsFormat vectorsFormat = new Lucene50TermVectorsFormat();
+  private final FieldInfosFormat fieldInfosFormat = new Lucene90FieldInfosFormat();
+  private final SegmentInfoFormat segmentInfosFormat = new Lucene86SegmentInfoFormat();
+  private final LiveDocsFormat liveDocsFormat = new Lucene50LiveDocsFormat();
+  private final CompoundFormat compoundFormat = new Lucene50CompoundFormat();
+  private final PostingsFormat defaultFormat;
+
+  private final PostingsFormat postingsFormat = new PerFieldPostingsFormat() {
+    @Override
+    public PostingsFormat getPostingsFormatForField(String field) {
+      return Lucene90Codec.this.getPostingsFormatForField(field);
+    }
+  };
+
+  private final DocValuesFormat docValuesFormat = new PerFieldDocValuesFormat() {
+    @Override
+    public DocValuesFormat getDocValuesFormatForField(String field) {
+      return Lucene90Codec.this.getDocValuesFormatForField(field);
+    }
+  };
+
+  private final VectorFormat vectorFormat = new Lucene90VectorFormat();
+
+  private final StoredFieldsFormat storedFieldsFormat;
+
+  /**
+   * Instantiates a new codec.
+   */
+  public Lucene90Codec() {
+    this(Lucene87StoredFieldsFormat.Mode.BEST_SPEED);
+  }
+
+  /**
+   * Instantiates a new codec, specifying the stored fields compression
+   * mode to use.
+   * @param mode stored fields compression mode to use for newly
+   *             flushed/merged segments.
+   */
+  public Lucene90Codec(Lucene87StoredFieldsFormat.Mode mode) {
+    super("Lucene90");
+    this.storedFieldsFormat = new Lucene87StoredFieldsFormat(Objects.requireNonNull(mode));
+    this.defaultFormat = new Lucene84PostingsFormat();
+  }
+
+  @Override
+  public final StoredFieldsFormat storedFieldsFormat() {
+    return storedFieldsFormat;
+  }
+
+  @Override
+  public final TermVectorsFormat termVectorsFormat() {
+    return vectorsFormat;
+  }
+
+  @Override
+  public final PostingsFormat postingsFormat() {
+    return postingsFormat;
+  }
+  @Override
+  public final FieldInfosFormat fieldInfosFormat() {
+    return fieldInfosFormat;
+  }
+
+  @Override
+  public final SegmentInfoFormat segmentInfoFormat() {
+    return segmentInfosFormat;
+  }
+
+  @Override
+  public final LiveDocsFormat liveDocsFormat() {
+    return liveDocsFormat;
+  }
+
+  @Override
+  public final CompoundFormat compoundFormat() {
+    return compoundFormat;
+  }
+
+  @Override
+  public final PointsFormat pointsFormat() {
+    return new Lucene86PointsFormat();
+  }
+
+  @Override
+  public final VectorFormat vectorFormat() {
+    return vectorFormat;
+  }
+
+  /** Returns the postings format that should be used for writing
+   *  new segments of <code>field</code>.
+   *
+   *  The default implementation always returns "Lucene84".
+   *  <p>
+   *  <b>WARNING:</b> if you subclass, you are responsible for index
+   *  backwards compatibility: future version of Lucene are only
+   *  guaranteed to be able to read the default implementation,
+   */
+  public PostingsFormat getPostingsFormatForField(String field) {
+    return defaultFormat;
+  }
+
+  /** Returns the docvalues format that should be used for writing
+   *  new segments of <code>field</code>.
+   *
+   *  The default implementation always returns "Lucene80".
+   *  <p>
+   *  <b>WARNING:</b> if you subclass, you are responsible for index
+   *  backwards compatibility: future version of Lucene are only
+   *  guaranteed to be able to read the default implementation.
+   */
+  public DocValuesFormat getDocValuesFormatForField(String field) {
+    return defaultDVFormat;
+  }
+
+  @Override
+  public final DocValuesFormat docValuesFormat() {
+    return docValuesFormat;
+  }
+
+  private final DocValuesFormat defaultDVFormat = DocValuesFormat.forName("Lucene80");
+
+  private final NormsFormat normsFormat = new Lucene80NormsFormat();
+
+  @Override
+  public final NormsFormat normsFormat() {
+    return normsFormat;
+  }
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90FieldInfosFormat.java

@@ -0,0 +1,339 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.codecs.lucene90;
+
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.Map;
+
+import org.apache.lucene.codecs.CodecUtil;
+import org.apache.lucene.codecs.DocValuesFormat;
+import org.apache.lucene.codecs.FieldInfosFormat;
+import org.apache.lucene.index.CorruptIndexException;
+import org.apache.lucene.index.DocValuesType;
+import org.apache.lucene.index.FieldInfo;
+import org.apache.lucene.index.FieldInfos;
+import org.apache.lucene.index.IndexFileNames;
+import org.apache.lucene.index.IndexOptions;
+import org.apache.lucene.index.SegmentInfo;
+import org.apache.lucene.index.VectorValues;
+import org.apache.lucene.store.ChecksumIndexInput;
+import org.apache.lucene.store.DataOutput;
+import org.apache.lucene.store.Directory;
+import org.apache.lucene.store.IOContext;
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.store.IndexOutput;
+
+/**
+ * Lucene 9.0 Field Infos format.
+ * <p>Field names are stored in the field info file, with suffix <code>.fnm</code>.
+ * <p>FieldInfos (.fnm) --&gt; Header,FieldsCount, &lt;FieldName,FieldNumber,
+ * FieldBits,DocValuesBits,DocValuesGen,Attributes,DimensionCount,DimensionNumBytes&gt; <sup>FieldsCount</sup>,Footer
+ * <p>Data types:
+ * <ul>
+ *   <li>Header --&gt; {@link CodecUtil#checkIndexHeader IndexHeader}</li>
+ *   <li>FieldsCount --&gt; {@link DataOutput#writeVInt VInt}</li>
+ *   <li>FieldName --&gt; {@link DataOutput#writeString String}</li>
+ *   <li>FieldBits, IndexOptions, DocValuesBits --&gt; {@link DataOutput#writeByte Byte}</li>
+ *   <li>FieldNumber, DimensionCount, DimensionNumBytes --&gt; {@link DataOutput#writeInt VInt}</li>
+ *   <li>Attributes --&gt; {@link DataOutput#writeMapOfStrings Map&lt;String,String&gt;}</li>
+ *   <li>DocValuesGen --&gt; {@link DataOutput#writeLong(long) Int64}</li>
+ *   <li>Footer --&gt; {@link CodecUtil#writeFooter CodecFooter}</li>
+ * </ul>
+ * Field Descriptions:
+ * <ul>
+ *   <li>FieldsCount: the number of fields in this file.</li>
+ *   <li>FieldName: name of the field as a UTF-8 String.</li>
+ *   <li>FieldNumber: the field's number. Note that unlike previous versions of
+ *       Lucene, the fields are not numbered implicitly by their order in the
+ *       file, instead explicitly.</li>
+ *   <li>FieldBits: a byte containing field options.
+ *     <ul>
+ *       <li>The low order bit (0x1) is one for fields that have term vectors
+ *           stored, and zero for fields without term vectors.</li>
+ *       <li>If the second lowest order-bit is set (0x2), norms are omitted for the
+ *           indexed field.</li>
+ *       <li>If the third lowest-order bit is set (0x4), payloads are stored for the
+ *           indexed field.</li>
+ *     </ul>
+ *   </li>
+ *   <li>IndexOptions: a byte containing index options.
+ *     <ul>
+ *       <li>0: not indexed</li>
+ *       <li>1: indexed as DOCS_ONLY</li>
+ *       <li>2: indexed as DOCS_AND_FREQS</li>
+ *       <li>3: indexed as DOCS_AND_FREQS_AND_POSITIONS</li>
+ *       <li>4: indexed as DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS</li>
+ *     </ul>
+ *   </li>
+ *   <li>DocValuesBits: a byte containing per-document value types. The type
+ *       recorded as two four-bit integers, with the high-order bits representing
+ *       <code>norms</code> options, and the low-order bits representing 
+ *       {@code DocValues} options. Each four-bit integer can be decoded as such:
+ *     <ul>
+ *       <li>0: no DocValues for this field.</li>
+ *       <li>1: NumericDocValues. ({@link DocValuesType#NUMERIC})</li>
+ *       <li>2: BinaryDocValues. ({@code DocValuesType#BINARY})</li>
+ *       <li>3: SortedDocValues. ({@code DocValuesType#SORTED})</li>
+ *      </ul>
+ *   </li>
+ *   <li>DocValuesGen is the generation count of the field's DocValues. If this is -1,
+ *       there are no DocValues updates to that field. Anything above zero means there 
+ *       are updates stored by {@link DocValuesFormat}.</li>
+ *   <li>Attributes: a key-value map of codec-private attributes.</li>
+ *   <li>PointDimensionCount, PointNumBytes: these are non-zero only if the field is
+ *       indexed as points, e.g. using {@link org.apache.lucene.document.LongPoint}</li>
+ *   <li>VectorDimension: it is non-zero if the field is indexed as vectors.</li>
+ *   <li>VectorDistFunction: a byte containing distance function used for similarity calculation.
+ *     <ul>
+ *       <li>0: no distance function is defined for this field.</li>
+ *       <li>1: EUCLIDEAN distance. ({@link org.apache.lucene.index.VectorValues.ScoreFunction#EUCLIDEAN})</li>
+ *       <li>2: DOT_PRODUCT score. ({@link org.apache.lucene.index.VectorValues.ScoreFunction#DOT_PRODUCT})</li>
+ *     </ul>
+ *   </li>
+ * </ul>
+ *
+ * @lucene.experimental
+ */
+public final class Lucene90FieldInfosFormat extends FieldInfosFormat {
+
+  /** Sole constructor. */
+  public Lucene90FieldInfosFormat() {
+  }
+  
+  @Override
+  public FieldInfos read(Directory directory, SegmentInfo segmentInfo, String segmentSuffix, IOContext context) throws IOException {
+    final String fileName = IndexFileNames.segmentFileName(segmentInfo.name, segmentSuffix, EXTENSION);
+    try (ChecksumIndexInput input = directory.openChecksumInput(fileName, context)) {
+      Throwable priorE = null;
+      FieldInfo infos[] = null;
+      try {
+        int version = CodecUtil.checkIndexHeader(input,
+                                   Lucene90FieldInfosFormat.CODEC_NAME,
+                                   Lucene90FieldInfosFormat.FORMAT_START,
+                                   Lucene90FieldInfosFormat.FORMAT_CURRENT,
+                                   segmentInfo.getId(), segmentSuffix);
+        
+        final int size = input.readVInt(); //read in the size
+        infos = new FieldInfo[size];
+        
+        // previous field's attribute map, we share when possible:
+        Map<String,String> lastAttributes = Collections.emptyMap();
+        
+        for (int i = 0; i < size; i++) {
+          String name = input.readString();
+          final int fieldNumber = input.readVInt();
+          if (fieldNumber < 0) {
+            throw new CorruptIndexException("invalid field number for field: " + name + ", fieldNumber=" + fieldNumber, input);
+          }
+          byte bits = input.readByte();
+          boolean storeTermVector = (bits & STORE_TERMVECTOR) != 0;
+          boolean omitNorms = (bits & OMIT_NORMS) != 0;
+          boolean storePayloads = (bits & STORE_PAYLOADS) != 0;
+          boolean isSoftDeletesField = (bits & SOFT_DELETES_FIELD) != 0;
+
+          final IndexOptions indexOptions = getIndexOptions(input, input.readByte());
+          
+          // DV Types are packed in one byte
+          final DocValuesType docValuesType = getDocValuesType(input, input.readByte());
+          final long dvGen = input.readLong();
+          Map<String,String> attributes = input.readMapOfStrings();
+          // just use the last field's map if its the same
+          if (attributes.equals(lastAttributes)) {
+            attributes = lastAttributes;
+          }
+          lastAttributes = attributes;
+          int pointDataDimensionCount = input.readVInt();
+          int pointNumBytes;
+          int pointIndexDimensionCount = pointDataDimensionCount;
+          if (pointDataDimensionCount != 0) {
+            if (version >= Lucene90FieldInfosFormat.FORMAT_SELECTIVE_INDEXING) {
+              pointIndexDimensionCount = input.readVInt();
+            }
+            pointNumBytes = input.readVInt();
+          } else {
+            pointNumBytes = 0;
+          }
+          final int vectorDimension = input.readVInt();
+          final VectorValues.ScoreFunction vectorDistFunc = getDistFunc(input, input.readByte());
+
+          try {
+            infos[i] = new FieldInfo(name, fieldNumber, storeTermVector, omitNorms, storePayloads, 
+                                     indexOptions, docValuesType, dvGen, attributes,
+                                     pointDataDimensionCount, pointIndexDimensionCount, pointNumBytes, vectorDimension, vectorDistFunc, isSoftDeletesField);
+            infos[i].checkConsistency();
+          } catch (IllegalStateException e) {
+            throw new CorruptIndexException("invalid fieldinfo for field: " + name + ", fieldNumber=" + fieldNumber, input, e);
+          }
+        }
+      } catch (Throwable exception) {
+        priorE = exception;
+      } finally {
+        CodecUtil.checkFooter(input, priorE);
+      }
+      return new FieldInfos(infos);
+    }
+  }
+  
+  static {
+    // We "mirror" DocValues enum values with the constants below; let's try to ensure if we add a new DocValuesType while this format is
+    // still used for writing, we remember to fix this encoding:
+    assert DocValuesType.values().length == 6;
+  }
+
+  private static byte docValuesByte(DocValuesType type) {
+    switch(type) {
+    case NONE:
+      return 0;
+    case NUMERIC:
+      return 1;
+    case BINARY:
+      return 2;
+    case SORTED:
+      return 3;
+    case SORTED_SET:
+      return 4;
+    case SORTED_NUMERIC:
+      return 5;
+    default:
+      // BUG
+      throw new AssertionError("unhandled DocValuesType: " + type);
+    }
+  }
+
+  private static DocValuesType getDocValuesType(IndexInput input, byte b) throws IOException {
+    switch(b) {
+    case 0:
+      return DocValuesType.NONE;
+    case 1:
+      return DocValuesType.NUMERIC;
+    case 2:
+      return DocValuesType.BINARY;
+    case 3:
+      return DocValuesType.SORTED;
+    case 4:
+      return DocValuesType.SORTED_SET;
+    case 5:
+      return DocValuesType.SORTED_NUMERIC;
+    default:
+      throw new CorruptIndexException("invalid docvalues byte: " + b, input);
+    }
+  }
+
+  private static VectorValues.ScoreFunction getDistFunc(IndexInput input, byte b) throws IOException {
+    if (b < 0 || b >= VectorValues.ScoreFunction.values().length) {
+      throw new CorruptIndexException("invalid distance function: " + b, input);
+    }
+    return VectorValues.ScoreFunction.values()[b];
+  }
+
+  static {
+    // We "mirror" IndexOptions enum values with the constants below; let's try to ensure if we add a new IndexOption while this format is
+    // still used for writing, we remember to fix this encoding:
+    assert IndexOptions.values().length == 5;
+  }
+
+  private static byte indexOptionsByte(IndexOptions indexOptions) {
+    switch (indexOptions) {
+    case NONE:
+      return 0;
+    case DOCS:
+      return 1;
+    case DOCS_AND_FREQS:
+      return 2;
+    case DOCS_AND_FREQS_AND_POSITIONS:
+      return 3;
+    case DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS:
+      return 4;
+    default:
+      // BUG:
+      throw new AssertionError("unhandled IndexOptions: " + indexOptions);
+    }
+  }
+  
+  private static IndexOptions getIndexOptions(IndexInput input, byte b) throws IOException {
+    switch (b) {
+    case 0:
+      return IndexOptions.NONE;
+    case 1:
+      return IndexOptions.DOCS;
+    case 2:
+      return IndexOptions.DOCS_AND_FREQS;
+    case 3:
+      return IndexOptions.DOCS_AND_FREQS_AND_POSITIONS;
+    case 4:
+      return IndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS;
+    default:
+      // BUG
+      throw new CorruptIndexException("invalid IndexOptions byte: " + b, input);
+    }
+  }
+
+  @Override
+  public void write(Directory directory, SegmentInfo segmentInfo, String segmentSuffix, FieldInfos infos, IOContext context) throws IOException {
+    final String fileName = IndexFileNames.segmentFileName(segmentInfo.name, segmentSuffix, EXTENSION);
+    try (IndexOutput output = directory.createOutput(fileName, context)) {
+      CodecUtil.writeIndexHeader(output, Lucene90FieldInfosFormat.CODEC_NAME, Lucene90FieldInfosFormat.FORMAT_CURRENT, segmentInfo.getId(), segmentSuffix);
+      output.writeVInt(infos.size());
+      for (FieldInfo fi : infos) {
+        fi.checkConsistency();
+
+        output.writeString(fi.name);
+        output.writeVInt(fi.number);
+
+        byte bits = 0x0;
+        if (fi.hasVectors()) bits |= STORE_TERMVECTOR;
+        if (fi.omitsNorms()) bits |= OMIT_NORMS;
+        if (fi.hasPayloads()) bits |= STORE_PAYLOADS;
+        if (fi.isSoftDeletesField()) bits |= SOFT_DELETES_FIELD;
+        output.writeByte(bits);
+
+        output.writeByte(indexOptionsByte(fi.getIndexOptions()));
+
+        // pack the DV type and hasNorms in one byte
+        output.writeByte(docValuesByte(fi.getDocValuesType()));
+        output.writeLong(fi.getDocValuesGen());
+        output.writeMapOfStrings(fi.attributes());
+        output.writeVInt(fi.getPointDimensionCount());
+        if (fi.getPointDimensionCount() != 0) {
+          output.writeVInt(fi.getPointIndexDimensionCount());
+          output.writeVInt(fi.getPointNumBytes());
+        }
+        output.writeVInt(fi.getVectorDimension());
+        output.writeByte((byte) fi.getVectorScoreFunction().ordinal());
+      }
+      CodecUtil.writeFooter(output);
+    }
+  }
+  
+  /** Extension of field infos */
+  static final String EXTENSION = "fnm";
+  
+  // Codec header
+  static final String CODEC_NAME = "Lucene90FieldInfos";
+  static final int FORMAT_START = 0;
+  static final int FORMAT_SOFT_DELETES = 1;
+  static final int FORMAT_SELECTIVE_INDEXING = 2;
+  static final int FORMAT_CURRENT = FORMAT_SELECTIVE_INDEXING;
+  
+  // Field flags
+  static final byte STORE_TERMVECTOR = 0x1;
+  static final byte OMIT_NORMS = 0x2;
+  static final byte STORE_PAYLOADS = 0x4;
+  static final byte SOFT_DELETES_FIELD = 0x8;
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90VectorFormat.java

@@ -0,0 +1,57 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.codecs.lucene90;
+
+import java.io.IOException;
+
+import org.apache.lucene.codecs.VectorFormat;
+import org.apache.lucene.codecs.VectorReader;
+import org.apache.lucene.codecs.VectorWriter;
+import org.apache.lucene.index.SegmentReadState;
+import org.apache.lucene.index.SegmentWriteState;
+
+/**
+ * Lucene 9.0 vector format, which encodes dense numeric vector values.
+ * TODO: add support for approximate KNN search.
+ */
+public final class Lucene90VectorFormat extends VectorFormat {
+
+  static final String META_CODEC_NAME = "Lucene90VectorFormatMeta";
+  static final String VECTOR_DATA_CODEC_NAME = "Lucene90VectorFormatData";
+
+  static final String META_EXTENSION = "vem";
+  static final String VECTOR_DATA_EXTENSION = "vec";
+
+  static final int VERSION_START = 0;
+  static final int VERSION_CURRENT = VERSION_START;
+
+  /** Sole constructor */
+  public Lucene90VectorFormat() {
+  }
+
+  @Override
+  public VectorWriter fieldsWriter(SegmentWriteState state) throws IOException {
+    return new Lucene90VectorWriter(state);
+  }
+
+  @Override
+  public VectorReader fieldsReader(SegmentReadState state) throws IOException {
+    return new Lucene90VectorReader(state);
+  }
+
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90VectorReader.java

@@ -0,0 +1,345 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.codecs.lucene90;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.FloatBuffer;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.apache.lucene.codecs.CodecUtil;
+import org.apache.lucene.codecs.VectorReader;
+import org.apache.lucene.index.CorruptIndexException;
+import org.apache.lucene.index.FieldInfo;
+import org.apache.lucene.index.FieldInfos;
+import org.apache.lucene.index.IndexFileNames;
+import org.apache.lucene.index.SegmentReadState;
+import org.apache.lucene.index.VectorValues;
+import org.apache.lucene.search.TopDocs;
+import org.apache.lucene.store.ChecksumIndexInput;
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.IOUtils;
+import org.apache.lucene.util.RamUsageEstimator;
+
+/**
+ * Reads vectors from the index segments.
+ * @lucene.experimental
+ */
+public final class Lucene90VectorReader extends VectorReader {
+
+  private final FieldInfos fieldInfos;
+  private final Map<String, FieldEntry> fields = new HashMap<>();
+  private final IndexInput vectorData;
+  private final int maxDoc;
+
+  Lucene90VectorReader(SegmentReadState state) throws IOException {
+    this.fieldInfos = state.fieldInfos;
+    this.maxDoc = state.segmentInfo.maxDoc();
+
+    String metaFileName = IndexFileNames.segmentFileName(state.segmentInfo.name, state.segmentSuffix, Lucene90VectorFormat.META_EXTENSION);
+    int versionMeta = -1;
+    try (ChecksumIndexInput meta = state.directory.openChecksumInput(metaFileName, state.context)) {
+      Throwable priorE = null;
+      try {
+        versionMeta = CodecUtil.checkIndexHeader(meta,
+            Lucene90VectorFormat.META_CODEC_NAME,
+            Lucene90VectorFormat.VERSION_START,
+            Lucene90VectorFormat.VERSION_CURRENT,
+            state.segmentInfo.getId(),
+            state.segmentSuffix);
+        readFields(meta, state.fieldInfos);
+      } catch (Throwable exception) {
+        priorE = exception;
+      } finally {
+        CodecUtil.checkFooter(meta, priorE);
+      }
+    }
+
+    boolean success = false;
+
+    String vectorDataFileName = IndexFileNames.segmentFileName(state.segmentInfo.name, state.segmentSuffix, Lucene90VectorFormat.VECTOR_DATA_EXTENSION);
+    this.vectorData = state.directory.openInput(vectorDataFileName, state.context);
+    try {
+      int versionVectorData = CodecUtil.checkIndexHeader(vectorData,
+          Lucene90VectorFormat.VECTOR_DATA_CODEC_NAME,
+          Lucene90VectorFormat.VERSION_START,
+          Lucene90VectorFormat.VERSION_CURRENT,
+          state.segmentInfo.getId(),
+          state.segmentSuffix);
+      if (versionMeta != versionVectorData) {
+        throw new CorruptIndexException("Format versions mismatch: meta=" + versionMeta + ", vector data=" + versionVectorData, vectorData);
+      }
+      CodecUtil.retrieveChecksum(vectorData);
+
+      success = true;
+    } finally {
+      if (!success) {
+        IOUtils.closeWhileHandlingException(this.vectorData);
+      }
+    }
+  }
+
+  private void readFields(ChecksumIndexInput meta, FieldInfos infos) throws IOException {
+    for (int fieldNumber = meta.readInt(); fieldNumber != -1; fieldNumber = meta.readInt()) {
+      FieldInfo info = infos.fieldInfo(fieldNumber);
+      if (info == null) {
+        throw new CorruptIndexException("Invalid field number: " + fieldNumber, meta);
+      }
+      int scoreFunctionId = meta.readInt();
+      if (scoreFunctionId < 0 || scoreFunctionId >= VectorValues.ScoreFunction.values().length) {
+        throw new CorruptIndexException("Invalid score function id: " + scoreFunctionId, meta);
+      }
+      VectorValues.ScoreFunction scoreFunction = VectorValues.ScoreFunction.values()[scoreFunctionId];
+      long vectorDataOffset = meta.readVLong();
+      long vectorDataLength = meta.readVLong();
+      int dimension = meta.readInt();
+      int size = meta.readInt();
+      int[] ordToDoc = new int[size];
+      for (int i = 0; i < size; i++) {
+        int doc = meta.readVInt();
+        ordToDoc[i] = doc;
+      }
+      FieldEntry fieldEntry = new FieldEntry(dimension, scoreFunction, maxDoc, vectorDataOffset, vectorDataLength,
+                                              ordToDoc);
+      fields.put(info.name, fieldEntry);
+    }
+  }
+
+  @Override
+  public long ramBytesUsed() {
+    long totalBytes = RamUsageEstimator.shallowSizeOfInstance(Lucene90VectorReader.class);
+    totalBytes += RamUsageEstimator.sizeOfMap(fields, RamUsageEstimator.shallowSizeOfInstance(FieldEntry.class));
+    for (FieldEntry entry : fields.values()) {
+      totalBytes += RamUsageEstimator.sizeOf(entry.ordToDoc);
+    }
+    return totalBytes;
+  }
+
+  @Override
+  public void checkIntegrity() throws IOException {
+    CodecUtil.checksumEntireFile(vectorData);
+  }
+
+  @Override
+  public VectorValues getVectorValues(String field) throws IOException {
+    FieldInfo info = fieldInfos.fieldInfo(field);
+    if (info == null) {
+      return null;
+    }
+    int dimension = info.getVectorDimension();
+    if (dimension == 0) {
+      return VectorValues.EMPTY;
+    }
+    FieldEntry fieldEntry = fields.get(field);
+    if (fieldEntry == null) {
+      // There is a FieldInfo, but no vectors. Should we have deleted the FieldInfo?
+      return null;
+    }
+    if (dimension != fieldEntry.dimension) {
+      throw new IllegalStateException("Inconsistent vector dimension for field=\"" + field + "\"; " + dimension + " != " + fieldEntry.dimension);
+    }
+    long numBytes = (long) fieldEntry.size() * dimension * Float.BYTES;
+    if (numBytes != fieldEntry.vectorDataLength) {
+      throw new IllegalStateException("Vector data length " + fieldEntry.vectorDataLength +
+          " not matching size=" + fieldEntry.size() + " * dim=" + dimension + " * 4 = " +
+          numBytes);
+    }
+    IndexInput bytesSlice = vectorData.slice("vector-data", fieldEntry.vectorDataOffset, fieldEntry.vectorDataLength);
+    return new OffHeapVectorValues(fieldEntry, bytesSlice);
+  }
+
+  @Override
+  public void close() throws IOException {
+    vectorData.close();
+  }
+
+  private static class FieldEntry {
+
+    final int dimension;
+    final VectorValues.ScoreFunction scoreFunction;
+    final int maxDoc;
+
+    final long vectorDataOffset;
+    final long vectorDataLength;
+    final int[] ordToDoc;
+
+    FieldEntry(int dimension, VectorValues.ScoreFunction scoreFunction, int maxDoc,
+               long vectorDataOffset, long vectorDataLength, int[] ordToDoc) {
+      this.dimension = dimension;
+      this.scoreFunction = scoreFunction;
+      this.maxDoc = maxDoc;
+      this.vectorDataOffset = vectorDataOffset;
+      this.vectorDataLength = vectorDataLength;
+      this.ordToDoc = ordToDoc;
+    }
+
+    int size() {
+      return ordToDoc.length;
+    }
+  }
+
+  /** Read the vector values from the index input. This supports both iterated and random access. */
+  private final static class OffHeapVectorValues extends VectorValues {
+
+    final FieldEntry fieldEntry;
+    final IndexInput dataIn;
+
+    final BytesRef binaryValue;
+    final ByteBuffer byteBuffer;
+    final FloatBuffer floatBuffer;
+    final int byteSize;
+    final float[] value;
+
+    int ord = -1;
+    int doc = -1;
+
+    OffHeapVectorValues(FieldEntry fieldEntry, IndexInput dataIn) {
+      this.fieldEntry = fieldEntry;
+      this.dataIn = dataIn;
+      byteSize = Float.BYTES * fieldEntry.dimension;
+      byteBuffer = ByteBuffer.allocate(byteSize);
+      floatBuffer = byteBuffer.asFloatBuffer();
+      value = new float[fieldEntry.dimension];
+      binaryValue = new BytesRef(byteBuffer.array(), byteBuffer.arrayOffset(), byteSize);
+    }
+
+    @Override
+    public int dimension() {
+      return fieldEntry.dimension;
+    }
+
+    @Override
+    public int size() {
+      return fieldEntry.size();
+    }
+
+    @Override
+    public ScoreFunction scoreFunction() {
+      return fieldEntry.scoreFunction;
+    }
+
+    @Override
+    public float[] vectorValue() throws IOException {
+      binaryValue();
+      floatBuffer.position(0);
+      floatBuffer.get(value, 0, fieldEntry.dimension);
+      return value;
+    }
+
+    @Override
+    public BytesRef binaryValue() throws IOException {
+      dataIn.seek(ord * byteSize);
+      dataIn.readBytes(byteBuffer.array(), byteBuffer.arrayOffset(), byteSize);
+      return binaryValue;
+    }
+
+    @Override
+    public int docID() {
+      return doc;
+    }
+
+    @Override
+    public int nextDoc() {
+      if (++ord >= size()) {
+        doc = NO_MORE_DOCS;
+      } else {
+        doc = fieldEntry.ordToDoc[ord];
+      }
+      return doc;
+    }
+
+    @Override
+    public int advance(int target) throws IOException {
+      // We could do better by log-binary search in ordToDoc, but this is never used
+      return slowAdvance(target);
+    }
+
+    @Override
+    public long cost() {
+      return fieldEntry.size();
+    }
+
+    @Override
+    public RandomAccess randomAccess() {
+      return new OffHeapRandomAccess(dataIn.clone());
+    }
+
+
+    class OffHeapRandomAccess implements VectorValues.RandomAccess {
+
+      final IndexInput dataIn;
+
+      final BytesRef binaryValue;
+      final ByteBuffer byteBuffer;
+      final FloatBuffer floatBuffer;
+      final int byteSize;
+      final float[] value;
+
+      OffHeapRandomAccess(IndexInput dataIn) {
+        this.dataIn = dataIn;
+        byteSize = Float.BYTES * dimension();
+        byteBuffer = ByteBuffer.allocate(byteSize);
+        floatBuffer = byteBuffer.asFloatBuffer();
+        value = new float[dimension()];
+        binaryValue = new BytesRef(byteBuffer.array(), byteBuffer.arrayOffset(), byteSize);
+      }
+
+      @Override
+      public int size() {
+        return fieldEntry.size();
+      }
+
+      @Override
+      public int dimension() {
+        return fieldEntry.dimension;
+      }
+
+      @Override
+      public VectorValues.ScoreFunction scoreFunction() {
+        return fieldEntry.scoreFunction;
+      }
+
+      @Override
+      public float[] vectorValue(int targetOrd) throws IOException {
+        readValue(targetOrd);
+        floatBuffer.position(0);
+        floatBuffer.get(value);
+        return value;
+      }
+
+      @Override
+      public BytesRef binaryValue(int targetOrd) throws IOException {
+        readValue(targetOrd);
+        return binaryValue;
+      }
+
+      private void readValue(int targetOrd) throws IOException {
+        long offset = targetOrd * byteSize;
+        dataIn.seek(offset);
+        dataIn.readBytes(byteBuffer.array(), byteBuffer.arrayOffset(), byteSize);
+      }
+
+      @Override
+      public TopDocs search(float[] vector, int topK, int fanout) throws IOException {
+        throw new UnsupportedOperationException();
+      }
+    }
+  }
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90VectorWriter.java

@@ -0,0 +1,127 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.codecs.lucene90;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.lucene.codecs.CodecUtil;
+import org.apache.lucene.codecs.VectorWriter;
+import org.apache.lucene.index.FieldInfo;
+import org.apache.lucene.index.IndexFileNames;
+import org.apache.lucene.index.SegmentWriteState;
+import org.apache.lucene.index.VectorValues;
+import org.apache.lucene.store.IndexOutput;
+import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.IOUtils;
+
+import static org.apache.lucene.search.DocIdSetIterator.NO_MORE_DOCS;
+
+/**
+ * Writes vector values and knn graphs to index segments.
+ * @lucene.experimental
+ */
+public final class Lucene90VectorWriter extends VectorWriter {
+
+  private final IndexOutput meta, vectorData;
+
+  private boolean finished;
+
+  Lucene90VectorWriter(SegmentWriteState state) throws IOException {
+    assert state.fieldInfos.hasVectorValues();
+
+    String metaFileName = IndexFileNames.segmentFileName(state.segmentInfo.name, state.segmentSuffix, Lucene90VectorFormat.META_EXTENSION);
+    meta = state.directory.createOutput(metaFileName, state.context);
+
+    String vectorDataFileName = IndexFileNames.segmentFileName(state.segmentInfo.name, state.segmentSuffix, Lucene90VectorFormat.VECTOR_DATA_EXTENSION);
+    vectorData = state.directory.createOutput(vectorDataFileName, state.context);
+
+    try {
+      CodecUtil.writeIndexHeader(meta,
+          Lucene90VectorFormat.META_CODEC_NAME,
+          Lucene90VectorFormat.VERSION_CURRENT,
+          state.segmentInfo.getId(), state.segmentSuffix);
+      CodecUtil.writeIndexHeader(vectorData,
+          Lucene90VectorFormat.VECTOR_DATA_CODEC_NAME,
+          Lucene90VectorFormat.VERSION_CURRENT,
+          state.segmentInfo.getId(), state.segmentSuffix);
+    } catch (IOException e) {
+      IOUtils.closeWhileHandlingException(this);
+    }
+  }
+
+  @Override
+  public void writeField(FieldInfo fieldInfo, VectorValues vectors) throws IOException {
+    long vectorDataOffset = vectorData.getFilePointer();
+    // TODO - use a better data structure; a bitset? DocsWithFieldSet is p.p. in o.a.l.index
+    List<Integer> docIds = new ArrayList<>();
+    int docV, ord = 0;
+    for (docV = vectors.nextDoc(); docV != NO_MORE_DOCS; docV = vectors.nextDoc(), ord++) {
+      writeVectorValue(vectors);
+      docIds.add(docV);
+      // TODO: write knn graph value
+    }
+    long vectorDataLength = vectorData.getFilePointer() - vectorDataOffset;
+    if (vectorDataLength > 0) {
+      writeMeta(fieldInfo, vectorDataOffset, vectorDataLength, docIds);
+    }
+  }
+
+  private void writeVectorValue(VectorValues vectors) throws IOException {
+    // write vector value
+    BytesRef binaryValue = vectors.binaryValue();
+    assert binaryValue.length == vectors.dimension() * Float.BYTES;
+    vectorData.writeBytes(binaryValue.bytes, binaryValue.offset, binaryValue.length);
+  }
+
+  private void writeMeta(FieldInfo field, long vectorDataOffset, long vectorDataLength, List<Integer> docIds) throws IOException {
+    meta.writeInt(field.number);
+    meta.writeInt(field.getVectorScoreFunction().ordinal());
+    meta.writeVLong(vectorDataOffset);
+    meta.writeVLong(vectorDataLength);
+    meta.writeInt(field.getVectorDimension());
+    meta.writeInt(docIds.size());
+    for (Integer docId : docIds) {
+      // TODO: delta-encode, or write as bitset
+      meta.writeVInt(docId);
+    }
+  }
+
+  @Override
+  public void finish() throws IOException {
+    if (finished) {
+      throw new IllegalStateException("already finished");
+    }
+    finished = true;
+
+    if (meta != null) {
+      // write end of fields marker
+      meta.writeInt(-1);
+      CodecUtil.writeFooter(meta);
+    }
+    if (vectorData != null) {
+      CodecUtil.writeFooter(vectorData);
+    }
+  }
+
+  @Override
+  public void close() throws IOException {
+    IOUtils.close(meta, vectorData);
+  }
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene90/package-info.java

@@ -0,0 +1,429 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Lucene 9.0 file format.
+ *
+ * <h2>Apache Lucene - Index File Formats</h2>
+ * <div>
+ * <ul>
+ * <li><a href="#Introduction">Introduction</a></li>
+ * <li><a href="#Definitions">Definitions</a>
+ *   <ul>
+ *   <li><a href="#Inverted_Indexing">Inverted Indexing</a></li>
+ *   <li><a href="#Types_of_Fields">Types of Fields</a></li>
+ *   <li><a href="#Segments">Segments</a></li>
+ *   <li><a href="#Document_Numbers">Document Numbers</a></li>
+ *   </ul>
+ * </li>
+ * <li><a href="#Overview">Index Structure Overview</a></li>
+ * <li><a href="#File_Naming">File Naming</a></li>
+ * <li><a href="#file-names">Summary of File Extensions</a>
+ *   <ul>
+ *   <li><a href="#Lock_File">Lock File</a></li>
+ *   <li><a href="#History">History</a></li>
+ *   <li><a href="#Limitations">Limitations</a></li>
+ *   </ul>
+ * </li>
+ * </ul>
+ * </div>
+ * <a id="Introduction"></a>
+ * <h3>Introduction</h3>
+ * <div>
+ * <p>This document defines the index file formats used in this version of Lucene.
+ * If you are using a different version of Lucene, please consult the copy of
+ * <code>docs/</code> that was distributed with
+ * the version you are using.</p>
+ * <p>This document attempts to provide a high-level definition of the Apache
+ * Lucene file formats.</p>
+ * </div>
+ * <a id="Definitions"></a>
+ * <h3>Definitions</h3>
+ * <div>
+ * <p>The fundamental concepts in Lucene are index, document, field and term.</p>
+ * <p>An index contains a sequence of documents.</p>
+ * <ul>
+ * <li>A document is a sequence of fields.</li>
+ * <li>A field is a named sequence of terms.</li>
+ * <li>A term is a sequence of bytes.</li>
+ * </ul>
+ * <p>The same sequence of bytes in two different fields is considered a different
+ * term. Thus terms are represented as a pair: the string naming the field, and the
+ * bytes within the field.</p>
+ * <a id="Inverted_Indexing"></a>
+ * <h4>Inverted Indexing</h4>
+ * <p>Lucene's index stores terms and statistics about those terms in order to make
+ * term-based search more efficient. Lucene's terms index falls into the family of indexes known as
+ * an <i>inverted index.</i> This is because it can list, for a term, the documents that contain
+ * it. This is the inverse of the natural relationship, in which documents list terms.</p>
+ * <a id="Types_of_Fields"></a>
+ * <h4>Types of Fields</h4>
+ * <p>In Lucene, fields may be <i>stored</i>, in which case their text is stored
+ * in the index literally, in a non-inverted manner. Fields that are inverted are
+ * called <i>indexed</i>. A field may be both stored and indexed.</p>
+ * <p>The text of a field may be <i>tokenized</i> into terms to be indexed, or the
+ * text of a field may be used literally as a term to be indexed. Most fields are
+ * tokenized, but sometimes it is useful for certain identifier fields to be
+ * indexed literally.</p>
+ * <p>See the {@link org.apache.lucene.document.Field Field}
+ * java docs for more information on Fields.</p>
+ * <a id="Segments"></a>
+ * <h4>Segments</h4>
+ * <p>Lucene indexes may be composed of multiple sub-indexes, or <i>segments</i>.
+ * Each segment is a fully independent index, which could be searched separately.
+ * Indexes evolve by:</p>
+ * <ol>
+ * <li>Creating new segments for newly added documents.</li>
+ * <li>Merging existing segments.</li>
+ * </ol>
+ * <p>Searches may involve multiple segments and/or multiple indexes, each index
+ * potentially composed of a set of segments.</p>
+ * <a id="Document_Numbers"></a>
+ * <h4>Document Numbers</h4>
+ * <p>Internally, Lucene refers to documents by an integer <i>document number</i>.
+ * The first document added to an index is numbered zero, and each subsequent
+ * document added gets a number one greater than the previous.</p>
+ * <p>Note that a document's number may change, so caution should be taken when
+ * storing these numbers outside of Lucene. In particular, numbers may change in
+ * the following situations:</p>
+ * <ul>
+ * <li>
+ * <p>The numbers stored in each segment are unique only within the segment, and
+ * must be converted before they can be used in a larger context. The standard
+ * technique is to allocate each segment a range of values, based on the range of
+ * numbers used in that segment. To convert a document number from a segment to an
+ * external value, the segment's <i>base</i> document number is added. To convert
+ * an external value back to a segment-specific value, the segment is identified
+ * by the range that the external value is in, and the segment's base value is
+ * subtracted. For example two five document segments might be combined, so that
+ * the first segment has a base value of zero, and the second of five. Document
+ * three from the second segment would have an external value of eight.</p>
+ * </li>
+ * <li>
+ * <p>When documents are deleted, gaps are created in the numbering. These are
+ * eventually removed as the index evolves through merging. Deleted documents are
+ * dropped when segments are merged. A freshly-merged segment thus has no gaps in
+ * its numbering.</p>
+ * </li>
+ * </ul>
+ * </div>
+ * <a id="Overview"></a>
+ * <h3>Index Structure Overview</h3>
+ * <div>
+ * <p>Each segment index maintains the following:</p>
+ * <ul>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene86.Lucene86SegmentInfoFormat Segment info}.
+ *    This contains metadata about a segment, such as the number of documents,
+ *    what files it uses, and information about how the segment is sorted
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene90.Lucene90FieldInfosFormat Field names}.
+ *    This contains metadata about the set of named fields used in the index.
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat Stored Field values}.
+ * This contains, for each document, a list of attribute-value pairs, where the attributes
+ * are field names. These are used to store auxiliary information about the document, such as
+ * its title, url, or an identifier to access a database. The set of stored fields are what is
+ * returned for each hit when searching. This is keyed by document number.
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term dictionary}.
+ * A dictionary containing all of the terms used in all of the
+ * indexed fields of all of the documents. The dictionary also contains the number
+ * of documents which contain the term, and pointers to the term's frequency and
+ * proximity data.
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term Frequency data}.
+ * For each term in the dictionary, the numbers of all the
+ * documents that contain that term, and the frequency of the term in that
+ * document, unless frequencies are omitted ({@link org.apache.lucene.index.IndexOptions#DOCS IndexOptions.DOCS})
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term Proximity data}.
+ * For each term in the dictionary, the positions that the
+ * term occurs in each document. Note that this will not exist if all fields in
+ * all documents omit position data.
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene80.Lucene80NormsFormat Normalization factors}.
+ * For each field in each document, a value is stored
+ * that is multiplied into the score for hits on that field.
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat Term Vectors}.
+ * For each field in each document, the term vector (sometimes
+ * called document vector) may be stored. A term vector consists of term text and
+ * term frequency. To add Term Vectors to your index see the
+ * {@link org.apache.lucene.document.Field Field} constructors
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat Per-document values}.
+ * Like stored values, these are also keyed by document
+ * number, but are generally intended to be loaded into main memory for fast
+ * access. Whereas stored values are generally intended for summary results from
+ * searches, per-document values are useful for things like scoring factors.
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene50.Lucene50LiveDocsFormat Live documents}.
+ * An optional file indicating which documents are live.
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene86.Lucene86PointsFormat Point values}.
+ * Optional pair of files, recording dimensionally indexed fields, to enable fast
+ * numeric range filtering and large numeric values like BigInteger and BigDecimal (1D)
+ * and geographic shape intersection (2D, 3D).
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene90.Lucene90VectorFormat Vector values}.
+ * The vector format stores numeric vectors in a format optimized for random access and computation,
+ * supporting high-dimensional nearest-neighbor search.
+ * </li>
+ * </ul>
+ * <p>Details on each of these are provided in their linked pages.</p>
+ * </div>
+ * <a id="File_Naming"></a>
+ * <h3>File Naming</h3>
+ * <div>
+ * <p>All files belonging to a segment have the same name with varying extensions.
+ * The extensions correspond to the different file formats described below. When
+ * using the Compound File format (default for small segments) these files (except
+ * for the Segment info file, the Lock file, and Deleted documents file) are collapsed
+ * into a single .cfs file (see below for details)</p>
+ * <p>Typically, all segments in an index are stored in a single directory,
+ * although this is not required.</p>
+ * <p>File names are never re-used. That is, when any file is saved
+ * to the Directory it is given a never before used filename. This is achieved
+ * using a simple generations approach. For example, the first segments file is
+ * segments_1, then segments_2, etc. The generation is a sequential long integer
+ * represented in alpha-numeric (base 36) form.</p>
+ * </div>
+ * <a id="file-names"></a>
+ * <h3>Summary of File Extensions</h3>
+ * <div>
+ * <p>The following table summarizes the names and extensions of the files in
+ * Lucene:</p>
+ * <table class="padding4" style="border-spacing: 1px; border-collapse: separate">
+ * <caption>lucene filenames by extension</caption>
+ * <tr>
+ * <th>Name</th>
+ * <th>Extension</th>
+ * <th>Brief Description</th>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.index.SegmentInfos Segments File}</td>
+ * <td>segments_N</td>
+ * <td>Stores information about a commit point</td>
+ * </tr>
+ * <tr>
+ * <td><a href="#Lock_File">Lock File</a></td>
+ * <td>write.lock</td>
+ * <td>The Write lock prevents multiple IndexWriters from writing to the same
+ * file.</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene86.Lucene86SegmentInfoFormat Segment Info}</td>
+ * <td>.si</td>
+ * <td>Stores metadata about a segment</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50CompoundFormat Compound File}</td>
+ * <td>.cfs, .cfe</td>
+ * <td>An optional "virtual" file consisting of all the other index files for
+ * systems that frequently run out of file handles.</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene60.Lucene60FieldInfosFormat Fields}</td>
+ * <td>.fnm</td>
+ * <td>Stores information about the fields</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat Field Index}</td>
+ * <td>.fdx</td>
+ * <td>Contains pointers to field data</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat Field Data}</td>
+ * <td>.fdt</td>
+ * <td>The stored fields for documents</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term Dictionary}</td>
+ * <td>.tim</td>
+ * <td>The term dictionary, stores term info</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Term Index}</td>
+ * <td>.tip</td>
+ * <td>The index into the Term Dictionary</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Frequencies}</td>
+ * <td>.doc</td>
+ * <td>Contains the list of docs which contain each term along with frequency</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Positions}</td>
+ * <td>.pos</td>
+ * <td>Stores position information about where a term occurs in the index</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat Payloads}</td>
+ * <td>.pay</td>
+ * <td>Stores additional per-position metadata information such as character offsets and user payloads</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene80.Lucene80NormsFormat Norms}</td>
+ * <td>.nvd, .nvm</td>
+ * <td>Encodes length and boost factors for docs and fields</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat Per-Document Values}</td>
+ * <td>.dvd, .dvm</td>
+ * <td>Encodes additional scoring factors or other per-document information.</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat Term Vector Index}</td>
+ * <td>.tvx</td>
+ * <td>Stores offset into the document data file</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat Term Vector Data}</td>
+ * <td>.tvd</td>
+ * <td>Contains term vector data.</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50LiveDocsFormat Live Documents}</td>
+ * <td>.liv</td>
+ * <td>Info about what documents are live</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene86.Lucene86PointsFormat Point values}</td>
+ * <td>.dii, .dim</td>
+ * <td>Holds indexed points</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene90.Lucene90VectorFormat Vector values}</td>
+ * <td>.vec, .vem</td>
+ * <td>Holds indexed vectors; <code>.vec</code> files contain the raw vector data, and
+ * <code>.vem</code> the vector metadata</td>
+ * </tr>
+ * </table>
+ * </div>
+ * <a id="Lock_File"></a>
+ * <h3>Lock File</h3>
+ * The write lock, which is stored in the index directory by default, is named
+ * "write.lock". If the lock directory is different from the index directory then
+ * the write lock will be named "XXXX-write.lock" where XXXX is a unique prefix
+ * derived from the full path to the index directory. When this file is present, a
+ * writer is currently modifying the index (adding or removing documents). This
+ * lock file ensures that only one writer is modifying the index at a time.
+ * <a id="History"></a>
+ * <h3>History</h3>
+ * <p>Compatibility notes are provided in this document, describing how file
+ * formats have changed from prior versions:</p>
+ * <ul>
+ * <li>In version 2.1, the file format was changed to allow lock-less commits (ie,
+ * no more commit lock). The change is fully backwards compatible: you can open a
+ * pre-2.1 index for searching or adding/deleting of docs. When the new segments
+ * file is saved (committed), it will be written in the new file format (meaning
+ * no specific "upgrade" process is needed). But note that once a commit has
+ * occurred, pre-2.1 Lucene will not be able to read the index.</li>
+ * <li>In version 2.3, the file format was changed to allow segments to share a
+ * single set of doc store (vectors &amp; stored fields) files. This allows for
+ * faster indexing in certain cases. The change is fully backwards compatible (in
+ * the same way as the lock-less commits change in 2.1).</li>
+ * <li>In version 2.4, Strings are now written as true UTF-8 byte sequence, not
+ * Java's modified UTF-8. See <a href="http://issues.apache.org/jira/browse/LUCENE-510">
+ * LUCENE-510</a> for details.</li>
+ * <li>In version 2.9, an optional opaque Map&lt;String,String&gt; CommitUserData
+ * may be passed to IndexWriter's commit methods (and later retrieved), which is
+ * recorded in the segments_N file. See <a href="http://issues.apache.org/jira/browse/LUCENE-1382">
+ * LUCENE-1382</a> for details. Also,
+ * diagnostics were added to each segment written recording details about why it
+ * was written (due to flush, merge; which OS/JRE was used; etc.). See issue
+ * <a href="http://issues.apache.org/jira/browse/LUCENE-1654">LUCENE-1654</a> for details.</li>
+ * <li>In version 3.0, compressed fields are no longer written to the index (they
+ * can still be read, but on merge the new segment will write them, uncompressed).
+ * See issue <a href="http://issues.apache.org/jira/browse/LUCENE-1960">LUCENE-1960</a>
+ * for details.</li>
+ * <li>In version 3.1, segments records the code version that created them. See
+ * <a href="http://issues.apache.org/jira/browse/LUCENE-2720">LUCENE-2720</a> for details.
+ * Additionally segments track explicitly whether or not they have term vectors.
+ * See <a href="http://issues.apache.org/jira/browse/LUCENE-2811">LUCENE-2811</a>
+ * for details.</li>
+ * <li>In version 3.2, numeric fields are written as natively to stored fields
+ * file, previously they were stored in text format only.</li>
+ * <li>In version 3.4, fields can omit position data while still indexing term
+ * frequencies.</li>
+ * <li>In version 4.0, the format of the inverted index became extensible via
+ * the {@link org.apache.lucene.codecs.Codec Codec} api. Fast per-document storage
+ * ({@code DocValues}) was introduced. Normalization factors need no longer be a
+ * single byte, they can be any {@link org.apache.lucene.index.NumericDocValues NumericDocValues}.
+ * Terms need not be unicode strings, they can be any byte sequence. Term offsets
+ * can optionally be indexed into the postings lists. Payloads can be stored in the
+ * term vectors.</li>
+ * <li>In version 4.1, the format of the postings list changed to use either
+ * of FOR compression or variable-byte encoding, depending upon the frequency
+ * of the term. Terms appearing only once were changed to inline directly into
+ * the term dictionary. Stored fields are compressed by default. </li>
+ * <li>In version 4.2, term vectors are compressed by default. DocValues has
+ * a new multi-valued type (SortedSet), that can be used for faceting/grouping/joining
+ * on multi-valued fields.</li>
+ * <li>In version 4.5, DocValues were extended to explicitly represent missing values.</li>
+ * <li>In version 4.6, FieldInfos were extended to support per-field DocValues generation, to
+ * allow updating NumericDocValues fields.</li>
+ * <li>In version 4.8, checksum footers were added to the end of each index file
+ * for improved data integrity. Specifically, the last 8 bytes of every index file
+ * contain the zlib-crc32 checksum of the file.</li>
+ * <li>In version 4.9, DocValues has a new multi-valued numeric type (SortedNumeric)
+ * that is suitable for faceting/sorting/analytics.</li>
+ * <li>In version 5.4, DocValues have been improved to store more information on disk:
+ * addresses for binary fields and ord indexes for multi-valued fields.</li>
+ * <li>In version 6.0, Points were added, for multi-dimensional range/distance search.</li>
+ * <li>In version 6.2, new Segment info format that reads/writes the index sort, to support index sorting.
+ * <li>In version 7.0, DocValues have been improved to better support sparse doc values
+ * thanks to an iterator API.</li>
+ * <li>In version 8.0, postings have been enhanced to record, for each block of
+ * doc ids, the (term freq, normalization factor) pairs that may trigger the
+ * maximum score of the block. This information is recorded alongside skip data
+ * in order to be able to skip blocks of doc ids if they may not produce high
+ * enough scores.
+ * Additionally doc values and norms has been extended with jump-tables to make access O(1)
+ * instead of O(n), where n is the number of elements to skip when advancing in the data.</li>
+ * <li>In version 8.4, postings, positions, offsets and payload lengths have move to a more
+ * performant encoding that is vectorized.</li>
+ * <li>In version 8.6, index sort serialization is delegated to the sorts themselves, to
+ * allow user-defined sorts to be used</li>
+ * <li>In version 8.7, stored fields compression became adaptive to better handle documents with
+ * smaller stored fields.</li>
+ * <li>In version 9.0, vector-valued fields were added.</li>
+ * </ul>
+ * <a id="Limitations"></a>
+ * <h3>Limitations</h3>
+ * <div>
+ * <p>Lucene uses a Java <code>int</code> to refer to
+ * document numbers, and the index file format uses an <code>Int32</code>
+ * on-disk to store document numbers. This is a limitation
+ * of both the index file format and the current implementation. Eventually these
+ * should be replaced with either <code>UInt64</code> values, or
+ * better yet, {@link org.apache.lucene.store.DataOutput#writeVInt VInt} values which have no limit.</p>
+ * </div>
+ */
+package org.apache.lucene.codecs.lucene90;

lucene/core/src/java/org/apache/lucene/document/FieldType.java

@@ -25,6 +25,7 @@ import org.apache.lucene.index.DocValuesType;
 import org.apache.lucene.index.IndexOptions;
 import org.apache.lucene.index.IndexableFieldType;
 import org.apache.lucene.index.PointValues;
+import org.apache.lucene.index.VectorValues;
 
 /**
  * Describes the properties of a field.
@@ -44,6 +45,8 @@ public class FieldType implements IndexableFieldType  {
   private int dimensionCount;
   private int indexDimensionCount;
   private int dimensionNumBytes;
+  private int vectorDimension;
+  private VectorValues.ScoreFunction vectorScoreFunction = VectorValues.ScoreFunction.NONE;
   private Map<String, String> attributes;
 
   /**
@@ -62,6 +65,8 @@ public class FieldType implements IndexableFieldType  {
     this.dimensionCount = ref.pointDimensionCount();
     this.indexDimensionCount = ref.pointIndexDimensionCount();
     this.dimensionNumBytes = ref.pointNumBytes();
+    this.vectorDimension = ref.vectorDimension();
+    this.vectorScoreFunction = ref.vectorScoreFunction();
     if (ref.getAttributes() != null) {
       this.attributes = new HashMap<>(ref.getAttributes());
     }
@@ -295,6 +300,7 @@ public class FieldType implements IndexableFieldType  {
    * Enables points indexing with selectable dimension indexing.
    */
   public void setDimensions(int dimensionCount, int indexDimensionCount, int dimensionNumBytes) {
+    checkIfFrozen();
     if (dimensionCount < 0) {
       throw new IllegalArgumentException("dimensionCount must be >= 0; got " + dimensionCount);
     }
@@ -351,6 +357,28 @@ public class FieldType implements IndexableFieldType  {
     return dimensionNumBytes;
   }
 
+  void setVectorDimensionsAndScoreFunction(int numDimensions, VectorValues.ScoreFunction distFunc) {
+    checkIfFrozen();
+    if (numDimensions <= 0) {
+      throw new IllegalArgumentException("vector numDimensions must be > 0; got " + numDimensions);
+    }
+    if (numDimensions > VectorValues.MAX_DIMENSIONS) {
+      throw new IllegalArgumentException("vector numDimensions must be <= VectorValues.MAX_DIMENSIONS (=" + VectorValues.MAX_DIMENSIONS + "); got " + numDimensions);
+    }
+    this.vectorDimension = numDimensions;
+    this.vectorScoreFunction = distFunc;
+  }
+
+  @Override
+  public int vectorDimension() {
+    return vectorDimension;
+  }
+
+  @Override
+  public VectorValues.ScoreFunction vectorScoreFunction() {
+    return vectorScoreFunction;
+  }
+
   /**
    * Puts an attribute value.
    * <p>

lucene/core/src/java/org/apache/lucene/document/VectorField.java

@@ -0,0 +1,99 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.document;
+
+import org.apache.lucene.index.VectorValues;
+
+/** A field that contains a single floating-point numeric vector (or none) for each document.
+ * Vectors are dense - that is, every dimension of a vector contains an explicit value, stored
+ * packed into an array (of type float[]) whose length is the vector dimension. Values can be
+ * retrieved using {@link VectorValues}, which is a forward-only docID-based iterator and also
+ * offers random-access by dense ordinal (not docId). VectorValues.ScoreFunctions may be
+ * used to compare vectors at query time (for example as part of result ranking). A VectorField may
+ * be associated with a score function that defines the metric used for nearest-neighbor search
+ * among vectors of that field, but at the moment this association is purely nominal: it is intended
+ * for future use by the to-be-implemented nearest neighbors search.
+ */
+public class VectorField extends Field {
+
+  private static FieldType getType(float[] v, VectorValues.ScoreFunction scoreFunction) {
+    if (v == null) {
+      throw new IllegalArgumentException("vector value must not be null");
+    }
+    int dimension = v.length;
+    if (dimension == 0) {
+      throw new IllegalArgumentException("cannot index an empty vector");
+    }
+    if (dimension > VectorValues.MAX_DIMENSIONS) {
+      throw new IllegalArgumentException("cannot index vectors with dimension greater than " + VectorValues.MAX_DIMENSIONS);
+    }
+    if (scoreFunction == null) {
+      throw new IllegalArgumentException("score function must not be null");
+    }
+    FieldType type = new FieldType();
+    type.setVectorDimensionsAndScoreFunction(dimension, scoreFunction);
+    type.freeze();
+    return type;
+  }
+
+  /** Creates a numeric vector field. Fields are single-valued: each document has either one value
+   * or no value. Vectors of a single field share the same dimension and score function.
+   *
+   *  @param name field name
+   *  @param vector value
+   *  @param scoreFunction a function defining vector proximity.
+   *  @throws IllegalArgumentException if any parameter is null, or the vector is empty or has dimension > 1024.
+   */
+  public VectorField(String name, float[] vector, VectorValues.ScoreFunction scoreFunction) {
+    super(name, getType(vector, scoreFunction));
+    fieldsData = vector;
+  }
+
+  /** Creates a numeric vector field with the default EUCLIDEAN (L2) score function. Fields are
+   * single-valued: each document has either one value or no value. Vectors of a single field share
+   * the same dimension and score function.
+   *
+   *  @param name field name
+   *  @param vector value
+   *  @throws IllegalArgumentException if any parameter is null, or the vector is empty or has dimension > 1024.
+   */
+  public VectorField(String name, float[] vector) {
+    this(name, vector, VectorValues.ScoreFunction.EUCLIDEAN);
+  }
+
+  /**
+   * Return the vector value of this field
+   */
+  public float[] vectorValue() {
+    return (float[]) fieldsData;
+  }
+
+  /**
+   * Set the vector value of this field
+   * @param value the value to set; must not be null, and length must match the field type
+   */
+  public void setVectorValue(float[] value) {
+    if (value == null) {
+      throw new IllegalArgumentException("value must not be null");
+    }
+    if (value.length != type.vectorDimension()) {
+      throw new IllegalArgumentException("value length " + value.length + " must match field dimension " + type.vectorDimension());
+    }
+    fieldsData = value;
+  }
+}

lucene/core/src/java/org/apache/lucene/index/CheckIndex.java

@@ -220,6 +220,9 @@ public final class CheckIndex implements Closeable {
 
       /** Status of index sort */
       public IndexSortStatus indexSortStatus;
+
+      /** Status of vectors */
+      public VectorValuesStatus vectorValuesStatus;
     }
     
     /**
@@ -374,7 +377,25 @@ public final class CheckIndex implements Closeable {
       /** Total number of fields with points. */
       public int totalValueFields;
       
-      /** Exception thrown during doc values test (null on success) */
+      /** Exception thrown during point values test (null on success) */
+      public Throwable error = null;
+    }
+
+    /**
+     * Status from testing VectorValues
+     */
+    public static final class VectorValuesStatus {
+
+      VectorValuesStatus() {
+      }
+
+      /** Total number of vector values tested. */
+      public long totalVectorValues;
+
+      /** Total number of fields with vectors. */
+      public int totalVectorFields;
+
+      /** Exception thrown during vector values test (null on success) */
       public Throwable error = null;
     }
 
@@ -731,6 +752,9 @@ public final class CheckIndex implements Closeable {
           // Test PointValues
           segInfoStat.pointsStatus = testPoints(reader, infoStream, failFast);
 
+          // Test VectorValues
+          segInfoStat.vectorValuesStatus = testVectors(reader, infoStream, failFast);
+
           // Test index sort
           segInfoStat.indexSortStatus = testSort(reader, indexSort, infoStream, failFast);
 
@@ -1955,6 +1979,65 @@ public final class CheckIndex implements Closeable {
     return status;
   }
 
+  /**
+   * Test the vectors index
+   * @lucene.experimental
+   */
+  public static Status.VectorValuesStatus testVectors(CodecReader reader, PrintStream infoStream, boolean failFast) throws IOException {
+    if (infoStream != null) {
+      infoStream.print("    test: vectors..............");
+    }
+    long startNS = System.nanoTime();
+    FieldInfos fieldInfos = reader.getFieldInfos();
+    Status.VectorValuesStatus status = new Status.VectorValuesStatus();
+    try {
+
+      if (fieldInfos.hasVectorValues()) {
+        for (FieldInfo fieldInfo : fieldInfos) {
+          if (fieldInfo.hasVectorValues()) {
+            int dimension = fieldInfo.getVectorDimension();
+            if (dimension <= 0) {
+              throw new RuntimeException("Field \"" + fieldInfo.name + "\" has vector values but dimension is " + dimension);
+            }
+            VectorValues values = reader.getVectorValues(fieldInfo.name);
+            if (values == null) {
+              continue;
+            }
+
+            status.totalVectorFields++;
+
+            int docCount = 0;
+            while (values.nextDoc() != NO_MORE_DOCS) {
+              int valueLength = values.vectorValue().length;
+              if (valueLength != dimension) {
+                throw new RuntimeException("Field \"" + fieldInfo.name + "\" has a value whose dimension=" + valueLength + " not matching the field's dimension=" + dimension);
+              }
+              ++docCount;
+            }
+            if (docCount != values.size()) {
+              throw new RuntimeException("Field \"" + fieldInfo.name + "\" has size=" + values.size() + " but when iterated, returns " + docCount + " docs with values");
+            }
+            status.totalVectorValues += docCount;
+          }
+        }
+      }
+
+      msg(infoStream, String.format(Locale.ROOT, "OK [%d fields, %d vectors] [took %.3f sec]", status.totalVectorFields, status.totalVectorValues, nsToSec(System.nanoTime()-startNS)));
+
+    } catch (Throwable e) {
+      if (failFast) {
+        throw IOUtils.rethrowAlways(e);
+      }
+      msg(infoStream, "ERROR: " + e);
+      status.error = e;
+      if (infoStream != null) {
+        e.printStackTrace(infoStream);
+      }
+    }
+
+    return status;
+  }
+
   /** Walks the entire N-dimensional points space, verifying that all points fall within the last cell's boundaries.
    *
    * @lucene.internal */

lucene/core/src/java/org/apache/lucene/index/CodecReader.java

@@ -26,6 +26,7 @@ import java.util.Objects;
 
 import org.apache.lucene.codecs.DocValuesProducer;
 import org.apache.lucene.codecs.FieldsProducer;
+import org.apache.lucene.codecs.VectorReader;
 import org.apache.lucene.codecs.NormsProducer;
 import org.apache.lucene.codecs.PointsReader;
 import org.apache.lucene.codecs.StoredFieldsReader;
@@ -77,6 +78,12 @@ public abstract class CodecReader extends LeafReader implements Accountable {
    * @lucene.internal
    */
   public abstract PointsReader getPointsReader();
+
+  /**
+   * Expert: retrieve underlying VectorReader
+   * @lucene.internal
+   */
+  public abstract VectorReader getVectorReader();
   
   @Override
   public final void document(int docID, StoredFieldVisitor visitor) throws IOException {
@@ -202,6 +209,18 @@ public abstract class CodecReader extends LeafReader implements Accountable {
     return getPointsReader().getValues(field);
   }
 
+  @Override
+  public final VectorValues getVectorValues(String field) throws IOException {
+    ensureOpen();
+    FieldInfo fi = getFieldInfos().fieldInfo(field);
+    if (fi == null || fi.getVectorDimension() == 0) {
+      // Field does not exist or does not index vectors
+      return null;
+    }
+
+    return getVectorReader().getVectorValues(field);
+  }
+
   @Override
   protected void doClose() throws IOException {
   }

lucene/core/src/java/org/apache/lucene/index/DocValuesLeafReader.java

@@ -47,6 +47,11 @@ abstract class DocValuesLeafReader extends LeafReader {
     throw new UnsupportedOperationException();
   }
 
+  @Override
+  public final VectorValues getVectorValues(String field) throws IOException {
+    throw new UnsupportedOperationException();
+  }
+
   @Override
   public final void checkIntegrity() throws IOException {
     throw new UnsupportedOperationException();

lucene/core/src/java/org/apache/lucene/index/FieldInfo.java

@@ -54,6 +54,9 @@ public final class FieldInfo {
   private int pointIndexDimensionCount;
   private int pointNumBytes;
 
+  private int vectorDimension;  // if it is a positive value, it means this field indexes vectors
+  private VectorValues.ScoreFunction vectorScoreFunction = VectorValues.ScoreFunction.NONE;
+
   // whether this field is used as the soft-deletes field
   private final boolean softDeletesField;
 
@@ -64,7 +67,8 @@ public final class FieldInfo {
    */
   public FieldInfo(String name, int number, boolean storeTermVector, boolean omitNorms, boolean storePayloads,
                    IndexOptions indexOptions, DocValuesType docValues, long dvGen, Map<String,String> attributes,
-                   int pointDimensionCount, int pointIndexDimensionCount, int pointNumBytes, boolean softDeletesField) {
+                   int pointDimensionCount, int pointIndexDimensionCount, int pointNumBytes,
+                   int vectorDimension, VectorValues.ScoreFunction vectorScoreFunction, boolean softDeletesField) {
     this.name = Objects.requireNonNull(name);
     this.number = number;
     this.docValuesType = Objects.requireNonNull(docValues, "DocValuesType must not be null (field: \"" + name + "\")");
@@ -83,6 +87,8 @@ public final class FieldInfo {
     this.pointDimensionCount = pointDimensionCount;
     this.pointIndexDimensionCount = pointIndexDimensionCount;
     this.pointNumBytes = pointNumBytes;
+    this.vectorDimension = vectorDimension;
+    this.vectorScoreFunction = vectorScoreFunction;
     this.softDeletesField = softDeletesField;
     this.checkConsistency();
   }
@@ -137,6 +143,14 @@ public final class FieldInfo {
       throw new IllegalStateException("field '" + name + "' cannot have a docvalues update generation without having docvalues");
     }
 
+    if (vectorDimension < 0) {
+      throw new IllegalStateException("vectorDimension must be >=0; got " + vectorDimension);
+    }
+
+    if (vectorDimension == 0 && vectorScoreFunction != VectorValues.ScoreFunction.NONE) {
+      throw new IllegalStateException("vector score function must be NONE when dimension = 0; got " + vectorScoreFunction);
+    }
+
     return true;
   }
 
@@ -232,6 +246,40 @@ public final class FieldInfo {
     return pointNumBytes;
   }
 
+  /** Record that this field is indexed with vectors, with the specified num of dimensions and distance function */
+  public void setVectorDimensionAndScoreFunction(int dimension, VectorValues.ScoreFunction scoreFunction) {
+    if (dimension < 0) {
+      throw new IllegalArgumentException("vector dimension must be >= 0; got " + dimension);
+    }
+    if (dimension > VectorValues.MAX_DIMENSIONS) {
+      throw new IllegalArgumentException("vector dimension must be <= VectorValues.MAX_DIMENSIONS (=" + VectorValues.MAX_DIMENSIONS + "); got " + dimension);
+    }
+    if (dimension == 0 && scoreFunction != VectorValues.ScoreFunction.NONE) {
+      throw new IllegalArgumentException("vector score function must be NONE when the vector dimension = 0; got " + scoreFunction);
+    }
+    if (vectorDimension != 0 && vectorDimension != dimension) {
+      throw new IllegalArgumentException("cannot change vector dimension from " + vectorDimension + " to " + dimension + " for field=\"" + name + "\"");
+    }
+    if (vectorScoreFunction != VectorValues.ScoreFunction.NONE && vectorScoreFunction != scoreFunction) {
+      throw new IllegalArgumentException("cannot change vector score function from " + vectorScoreFunction + " to " + scoreFunction + " for field=\"" + name + "\"");
+    }
+
+    this.vectorDimension = dimension;
+    this.vectorScoreFunction = scoreFunction;
+
+    assert checkConsistency();
+  }
+
+  /** Returns the number of dimensions of the vector value */
+  public int getVectorDimension() {
+    return vectorDimension;
+  }
+
+  /** Returns {@link org.apache.lucene.index.VectorValues.ScoreFunction} for the field */
+  public VectorValues.ScoreFunction getVectorScoreFunction() {
+    return vectorScoreFunction;
+  }
+
   /** Record that this field is indexed with docvalues, with the specified type */
   public void setDocValuesType(DocValuesType type) {
     if (type == null) {
@@ -336,6 +384,13 @@ public final class FieldInfo {
   public boolean hasVectors() {
     return storeTermVector;
   }
+
+  /**
+   * Returns whether any (numeric) vector values exist for this field
+   */
+  public boolean hasVectorValues() {
+    return vectorDimension > 0;
+  }
   
   /**
    * Get a codec attribute value, or null if it does not exist

lucene/core/src/java/org/apache/lucene/index/FieldInfos.java

@@ -48,6 +48,7 @@ public class FieldInfos implements Iterable<FieldInfo> {
   private final boolean hasNorms;
   private final boolean hasDocValues;
   private final boolean hasPointValues;
+  private final boolean hasVectorValues;
   private final String softDeletesField;
   
   // used only by fieldInfo(int)
@@ -68,6 +69,7 @@ public class FieldInfos implements Iterable<FieldInfo> {
     boolean hasNorms = false;
     boolean hasDocValues = false;
     boolean hasPointValues = false;
+    boolean hasVectorValues = false;
     String softDeletesField = null;
 
     int size = 0; // number of elements in byNumberTemp, number of used array slots
@@ -99,6 +101,7 @@ public class FieldInfos implements Iterable<FieldInfo> {
       hasDocValues |= info.getDocValuesType() != DocValuesType.NONE;
       hasPayloads |= info.hasPayloads();
       hasPointValues |= (info.getPointDimensionCount() != 0);
+      hasVectorValues |= (info.getVectorDimension() != 0);
       if (info.isSoftDeletesField()) {
         if (softDeletesField != null && softDeletesField.equals(info.name) == false) {
           throw new IllegalArgumentException("multiple soft-deletes fields [" + info.name + ", " + softDeletesField + "]");
@@ -115,6 +118,7 @@ public class FieldInfos implements Iterable<FieldInfo> {
     this.hasNorms = hasNorms;
     this.hasDocValues = hasDocValues;
     this.hasPointValues = hasPointValues;
+    this.hasVectorValues = hasVectorValues;
     this.softDeletesField = softDeletesField;
 
     List<FieldInfo> valuesTemp = new ArrayList<>();
@@ -204,6 +208,11 @@ public class FieldInfos implements Iterable<FieldInfo> {
     return hasPointValues;
   }
 
+  /** Returns true if any fields have VectorValues */
+  public boolean hasVectorValues() {
+    return hasVectorValues;
+  }
+
   /** Returns the soft-deletes field name if exists; otherwise returns null */
   public String getSoftDeletesField() {
     return softDeletesField;
@@ -261,6 +270,16 @@ public class FieldInfos implements Iterable<FieldInfo> {
       this.dimensionNumBytes = dimensionNumBytes;
     }
   }
+
+  static final class FieldVectorProperties {
+    final int numDimensions;
+    final VectorValues.ScoreFunction scoreFunction;
+
+    FieldVectorProperties(int numDimensions, VectorValues.ScoreFunction scoreFunction) {
+      this.numDimensions = numDimensions;
+      this.scoreFunction = scoreFunction;
+    }
+  }
   
   static final class FieldNumbers {
     
@@ -274,6 +293,8 @@ public class FieldInfos implements Iterable<FieldInfo> {
 
     private final Map<String,FieldDimensions> dimensions;
 
+    private final Map<String,FieldVectorProperties> vectorProps;
+
     // TODO: we should similarly catch an attempt to turn
     // norms back on after they were already committed; today
     // we silently discard the norm but this is badly trappy
@@ -288,6 +309,7 @@ public class FieldInfos implements Iterable<FieldInfo> {
       this.indexOptions = new HashMap<>();
       this.docValuesType = new HashMap<>();
       this.dimensions = new HashMap<>();
+      this.vectorProps = new HashMap<>();
       this.softDeletesFieldName = softDeletesFieldName;
     }
     
@@ -297,7 +319,7 @@ public class FieldInfos implements Iterable<FieldInfo> {
      * number assigned if possible otherwise the first unassigned field number
      * is used as the field number.
      */
-    synchronized int addOrGet(String fieldName, int preferredFieldNumber, IndexOptions indexOptions, DocValuesType dvType, int dimensionCount, int indexDimensionCount, int dimensionNumBytes, boolean isSoftDeletesField) {
+    synchronized int addOrGet(String fieldName, int preferredFieldNumber, IndexOptions indexOptions, DocValuesType dvType, int dimensionCount, int indexDimensionCount, int dimensionNumBytes, int vectorDimension, VectorValues.ScoreFunction scoreFunction, boolean isSoftDeletesField) {
       if (indexOptions != IndexOptions.NONE) {
         IndexOptions currentOpts = this.indexOptions.get(fieldName);
         if (currentOpts == null) {
@@ -330,6 +352,19 @@ public class FieldInfos implements Iterable<FieldInfo> {
           dimensions.put(fieldName, new FieldDimensions(dimensionCount, indexDimensionCount, dimensionNumBytes));
         }
       }
+      if (vectorDimension != 0) {
+        FieldVectorProperties props = vectorProps.get(fieldName);
+        if (props != null) {
+          if (props.numDimensions != vectorDimension) {
+            throw new IllegalArgumentException("cannot change vector dimension from " + props.numDimensions + " to " + vectorDimension + " for field=\"" + fieldName + "\"");
+          }
+          if (props.scoreFunction != scoreFunction) {
+            throw new IllegalArgumentException("cannot change vector score function from " + props.scoreFunction + " to " + scoreFunction + " for field=\"" + fieldName + "\"");
+          }
+        } else {
+          vectorProps.put(fieldName, new FieldVectorProperties(vectorDimension, scoreFunction));
+        }
+      }
       Integer fieldNumber = nameToNumber.get(fieldName);
       if (fieldNumber == null) {
         final Integer preferredBoxed = Integer.valueOf(preferredFieldNumber);
@@ -408,6 +443,24 @@ public class FieldInfos implements Iterable<FieldInfo> {
       }
     }
 
+    synchronized void verifyConsistentVectorProperties(Integer number, String name, int numDimensions, VectorValues.ScoreFunction scoreFunction) {
+      if (name.equals(numberToName.get(number)) == false) {
+        throw new IllegalArgumentException("field number " + number + " is already mapped to field name \"" + numberToName.get(number) + "\", not \"" + name + "\"");
+      }
+      if (number.equals(nameToNumber.get(name)) == false) {
+        throw new IllegalArgumentException("field name \"" + name + "\" is already mapped to field number \"" + nameToNumber.get(name) + "\", not \"" + number + "\"");
+      }
+      FieldVectorProperties props = vectorProps.get(name);
+      if (props != null) {
+        if (props.numDimensions != numDimensions) {
+          throw new IllegalArgumentException("cannot change vector dimension from " + props.numDimensions + " to " + numDimensions + " for field=\"" + name + "\"");
+        }
+        if (props.scoreFunction != scoreFunction) {
+          throw new IllegalArgumentException("cannot change vector score function from " + props.scoreFunction + " to " + scoreFunction + " for field=\"" + name + "\"");
+        }
+      }
+    }
+
     /**
      * Returns true if the {@code fieldName} exists in the map and is of the
      * same {@code dvType}.
@@ -456,6 +509,17 @@ public class FieldInfos implements Iterable<FieldInfo> {
       verifyConsistentDimensions(number, name, dimensionCount, indexDimensionCount, dimensionNumBytes);
       dimensions.put(name, new FieldDimensions(dimensionCount, indexDimensionCount, dimensionNumBytes));
     }
+
+    synchronized void setVectorDimensionsAndScoreFunction(int number, String name, int numDimensions, VectorValues.ScoreFunction scoreFunction) {
+      if (numDimensions <= 0) {
+        throw new IllegalArgumentException("vector numDimensions must be > 0; got " + numDimensions);
+      }
+      if (numDimensions > VectorValues.MAX_DIMENSIONS) {
+        throw new IllegalArgumentException("vector numDimensions must be <= VectorValues.MAX_DIMENSIONS (=" + VectorValues.MAX_DIMENSIONS + "); got " + numDimensions);
+      }
+      verifyConsistentVectorProperties(number, name, numDimensions, scoreFunction);
+      vectorProps.put(name, new FieldVectorProperties(numDimensions, scoreFunction));
+    }
   }
   
   static final class Builder {
@@ -489,8 +553,8 @@ public class FieldInfos implements Iterable<FieldInfo> {
         // before then we'll get the same name and number,
         // else we'll allocate a new one:
         final boolean isSoftDeletesField = name.equals(globalFieldNumbers.softDeletesFieldName);
-        final int fieldNumber = globalFieldNumbers.addOrGet(name, -1, IndexOptions.NONE, DocValuesType.NONE, 0, 0, 0, isSoftDeletesField);
-        fi = new FieldInfo(name, fieldNumber, false, false, false, IndexOptions.NONE, DocValuesType.NONE, -1, new HashMap<>(), 0, 0, 0, isSoftDeletesField);
+        final int fieldNumber = globalFieldNumbers.addOrGet(name, -1, IndexOptions.NONE, DocValuesType.NONE, 0, 0, 0, 0, VectorValues.ScoreFunction.NONE, isSoftDeletesField);
+        fi = new FieldInfo(name, fieldNumber, false, false, false, IndexOptions.NONE, DocValuesType.NONE, -1, new HashMap<>(), 0, 0, 0, 0, VectorValues.ScoreFunction.NONE, isSoftDeletesField);
         assert !byName.containsKey(fi.name);
         globalFieldNumbers.verifyConsistent(Integer.valueOf(fi.number), fi.name, DocValuesType.NONE);
         byName.put(fi.name, fi);
@@ -505,6 +569,7 @@ public class FieldInfos implements Iterable<FieldInfo> {
                                           DocValuesType docValues, long dvGen,
                                           Map<String, String> attributes,
                                           int dataDimensionCount, int indexDimensionCount, int dimensionNumBytes,
+                                          int vectorDimension, VectorValues.ScoreFunction vectorScoreFunction,
                                           boolean isSoftDeletesField) {
       assert assertNotFinished();
       if (docValues == null) {
@@ -522,8 +587,8 @@ public class FieldInfos implements Iterable<FieldInfo> {
         // number for this field.  If the field was seen
         // before then we'll get the same name and number,
         // else we'll allocate a new one:
-        final int fieldNumber = globalFieldNumbers.addOrGet(name, preferredFieldNumber, indexOptions, docValues, dataDimensionCount, indexDimensionCount, dimensionNumBytes, isSoftDeletesField);
-        fi = new FieldInfo(name, fieldNumber, storeTermVector, omitNorms, storePayloads, indexOptions, docValues, dvGen, attributes, dataDimensionCount, indexDimensionCount, dimensionNumBytes, isSoftDeletesField);
+        final int fieldNumber = globalFieldNumbers.addOrGet(name, preferredFieldNumber, indexOptions, docValues, dataDimensionCount, indexDimensionCount, dimensionNumBytes, vectorDimension, vectorScoreFunction, isSoftDeletesField);
+        fi = new FieldInfo(name, fieldNumber, storeTermVector, omitNorms, storePayloads, indexOptions, docValues, dvGen, attributes, dataDimensionCount, indexDimensionCount, dimensionNumBytes, vectorDimension, vectorScoreFunction, isSoftDeletesField);
         assert !byName.containsKey(fi.name);
         globalFieldNumbers.verifyConsistent(Integer.valueOf(fi.number), fi.name, fi.getDocValuesType());
         byName.put(fi.name, fi);
@@ -558,6 +623,7 @@ public class FieldInfos implements Iterable<FieldInfo> {
                                  fi.getIndexOptions(), fi.getDocValuesType(), dvGen,
                                  fi.attributes(),
                                  fi.getPointDimensionCount(), fi.getPointIndexDimensionCount(), fi.getPointNumBytes(),
+                                 fi.getVectorDimension(), fi.getVectorScoreFunction(),
                                  fi.isSoftDeletesField());
     }
     

lucene/core/src/java/org/apache/lucene/index/FilterCodecReader.java

@@ -23,6 +23,7 @@ import java.util.Objects;
 
 import org.apache.lucene.codecs.DocValuesProducer;
 import org.apache.lucene.codecs.FieldsProducer;
+import org.apache.lucene.codecs.VectorReader;
 import org.apache.lucene.codecs.NormsProducer;
 import org.apache.lucene.codecs.PointsReader;
 import org.apache.lucene.codecs.StoredFieldsReader;
@@ -101,6 +102,11 @@ public abstract class FilterCodecReader extends CodecReader {
     return in.getPointsReader();
   }
 
+  @Override
+  public VectorReader getVectorReader() {
+    return in.getVectorReader();
+  }
+
   @Override
   public int numDocs() {
     return in.numDocs();

lucene/core/src/java/org/apache/lucene/index/FilterLeafReader.java

@@ -330,6 +330,11 @@ public abstract class FilterLeafReader extends LeafReader {
     return in.getPointValues(field);
   }
 
+  @Override
+  public VectorValues getVectorValues(String field) throws IOException {
+    return in.getVectorValues(field);
+  }
+
   @Override
   public Fields getTermVectors(int docID)
           throws IOException {

lucene/core/src/java/org/apache/lucene/index/IndexWriter.java

@@ -1184,7 +1184,8 @@ public class IndexWriter implements Closeable, TwoPhaseCommit, Accountable,
     for(SegmentCommitInfo info : segmentInfos) {
       FieldInfos fis = readFieldInfos(info);
       for(FieldInfo fi : fis) {
-        map.addOrGet(fi.name, fi.number, fi.getIndexOptions(), fi.getDocValuesType(), fi.getPointDimensionCount(), fi.getPointIndexDimensionCount(), fi.getPointNumBytes(), fi.isSoftDeletesField());
+        map.addOrGet(fi.name, fi.number, fi.getIndexOptions(), fi.getDocValuesType(), fi.getPointDimensionCount(), fi.getPointIndexDimensionCount(), fi.getPointNumBytes(),
+                     fi.getVectorDimension(), fi.getVectorScoreFunction(), fi.isSoftDeletesField());
       }
     }
 
@@ -1921,7 +1922,7 @@ public class IndexWriter implements Closeable, TwoPhaseCommit, Accountable,
       if (globalFieldNumberMap.contains(f.name(), dvType) == false) {
         // if this field doesn't exists we try to add it. if it exists and the DV type doesn't match we
         // get a consistent error message as if you try to do that during an indexing operation.
-        globalFieldNumberMap.addOrGet(f.name(), -1, IndexOptions.NONE, dvType, 0, 0, 0, f.name().equals(config.softDeletesField));
+        globalFieldNumberMap.addOrGet(f.name(), -1, IndexOptions.NONE, dvType, 0, 0, 0, 0, VectorValues.ScoreFunction.NONE, f.name().equals(config.softDeletesField));
         assert globalFieldNumberMap.contains(f.name(), dvType);
       }
       if (config.getIndexSortFields().contains(f.name())) {
@@ -2966,7 +2967,9 @@ public class IndexWriter implements Closeable, TwoPhaseCommit, Accountable,
             FieldInfos fis = readFieldInfos(info);
             for(FieldInfo fi : fis) {
               // This will throw exceptions if any of the incoming fields have an illegal schema change:
-              globalFieldNumberMap.addOrGet(fi.name, fi.number, fi.getIndexOptions(), fi.getDocValuesType(), fi.getPointDimensionCount(), fi.getPointIndexDimensionCount(), fi.getPointNumBytes(), fi.isSoftDeletesField());
+              globalFieldNumberMap.addOrGet(fi.name, fi.number, fi.getIndexOptions(), fi.getDocValuesType(),
+                                            fi.getPointDimensionCount(), fi.getPointIndexDimensionCount(), fi.getPointNumBytes(),
+                                            fi.getVectorDimension(), fi.getVectorScoreFunction(), fi.isSoftDeletesField());
             }
             infos.add(copySegmentAsIs(info, newSegName, context));
           }

lucene/core/src/java/org/apache/lucene/index/IndexableFieldType.java

@@ -114,6 +114,16 @@ public interface IndexableFieldType {
    */
   public int pointNumBytes();
 
+  /**
+   * The number of dimensions of the field's vector value
+   */
+  public int vectorDimension();
+
+  /**
+   * The {@link org.apache.lucene.index.VectorValues.ScoreFunction} of the field's vector value
+   */
+  public VectorValues.ScoreFunction vectorScoreFunction();
+
   /**
    * Attributes for the field type.
    *

lucene/core/src/java/org/apache/lucene/index/IndexingChain.java

@@ -32,12 +32,15 @@ import org.apache.lucene.analysis.Analyzer;
 import org.apache.lucene.analysis.TokenStream;
 import org.apache.lucene.codecs.DocValuesConsumer;
 import org.apache.lucene.codecs.DocValuesFormat;
+import org.apache.lucene.codecs.VectorFormat;
+import org.apache.lucene.codecs.VectorWriter;
 import org.apache.lucene.codecs.NormsConsumer;
 import org.apache.lucene.codecs.NormsFormat;
 import org.apache.lucene.codecs.NormsProducer;
 import org.apache.lucene.codecs.PointsFormat;
 import org.apache.lucene.codecs.PointsWriter;
 import org.apache.lucene.document.FieldType;
+import org.apache.lucene.document.VectorField;
 import org.apache.lucene.search.DocIdSetIterator;
 import org.apache.lucene.search.Sort;
 import org.apache.lucene.search.SortField;
@@ -180,7 +183,6 @@ final class IndexingChain implements Accountable {
       public FieldInfos getFieldInfos() {
         return fieldInfos.finish();
       }
-
     };
   }
 
@@ -230,6 +232,12 @@ final class IndexingChain implements Accountable {
     if (infoStream.isEnabled("IW")) {
       infoStream.message("IW", ((System.nanoTime()-t0)/1000000) + " msec to write points");
     }
+
+    t0 = System.nanoTime();
+    writeVectors(state, sortMap);
+    if (infoStream.isEnabled("IW")) {
+      infoStream.message("IW", ((System.nanoTime()-t0)/1000000) + " msec to write vectors");
+    }
     
     // it's possible all docs hit non-aborting exceptions...
     t0 = System.nanoTime();
@@ -374,6 +382,50 @@ final class IndexingChain implements Accountable {
     }
   }
 
+  /** Writes all buffered vectors. */
+  private void writeVectors(SegmentWriteState state, Sorter.DocMap sortMap) throws IOException {
+    VectorWriter vectorWriter = null;
+    boolean success = false;
+    try {
+      for (int i = 0; i<fieldHash.length; i++) {
+        PerField perField = fieldHash[i];
+        while (perField != null) {
+          if (perField.vectorValuesWriter != null) {
+            if (perField.fieldInfo.getVectorDimension() == 0) {
+              // BUG
+              throw new AssertionError("segment=" + state.segmentInfo + ": field=\"" + perField.fieldInfo.name + "\" has no vectors but wrote them");
+            }
+            if (vectorWriter == null) {
+              // lazy init
+              VectorFormat fmt = state.segmentInfo.getCodec().vectorFormat();
+              if (fmt == null) {
+                throw new IllegalStateException("field=\"" + perField.fieldInfo.name + "\" was indexed as vectors but codec does not support vectors");
+              }
+              vectorWriter = fmt.fieldsWriter(state);
+            }
+
+            perField.vectorValuesWriter.flush(sortMap, vectorWriter);
+            perField.vectorValuesWriter = null;
+          } else if (perField.fieldInfo.getVectorDimension() != 0) {
+            // BUG
+            throw new AssertionError("segment=" + state.segmentInfo + ": field=\"" + perField.fieldInfo.name + "\" has vectors but did not write them");
+          }
+          perField = perField.next;
+        }
+      }
+      if (vectorWriter != null) {
+        vectorWriter.finish();
+      }
+      success = true;
+    } finally {
+      if (success) {
+        IOUtils.close(vectorWriter);
+      } else {
+        IOUtils.closeWhileHandlingException(vectorWriter);
+      }
+    }
+  }
+
   private void writeNorms(SegmentWriteState state, Sorter.DocMap sortMap) throws IOException {
     boolean success = false;
     NormsConsumer normsConsumer = null;
@@ -562,6 +614,12 @@ final class IndexingChain implements Accountable {
       }
       indexPoint(docID, fp, field);
     }
+    if (fieldType.vectorDimension() != 0) {
+      if (fp == null) {
+        fp = getOrAddField(fieldName, fieldType, false);
+      }
+      indexVector(docID, fp, field);
+    }
     
     return fieldCount;
   }
@@ -722,6 +780,24 @@ final class IndexingChain implements Accountable {
     }
   }
 
+  /** Called from processDocument to index one field's vector value */
+  private void indexVector(int docID, PerField fp, IndexableField field) {
+    int dimension = field.fieldType().vectorDimension();
+    VectorValues.ScoreFunction scoreFunction = field.fieldType().vectorScoreFunction();
+
+    // Record dimensions and distance function for this field; this setter will throw IllegalArgExc if
+    // the dimensions or distance function were already set to something different:
+    if (fp.fieldInfo.getVectorDimension() == 0) {
+      fieldInfos.globalFieldNumbers.setVectorDimensionsAndScoreFunction(fp.fieldInfo.number, fp.fieldInfo.name, dimension, scoreFunction);
+    }
+    fp.fieldInfo.setVectorDimensionAndScoreFunction(dimension, scoreFunction);
+
+    if (fp.vectorValuesWriter == null) {
+      fp.vectorValuesWriter = new VectorValuesWriter(fp.fieldInfo, bytesUsed);
+    }
+    fp.vectorValuesWriter.addValue(docID, ((VectorField) field).vectorValue());
+  }
+
   /** Returns a previously created {@link PerField}, or null
    *  if this field name wasn't seen yet. */
   private PerField getPerField(String name) {
@@ -820,6 +896,9 @@ final class IndexingChain implements Accountable {
     // Non-null if this field ever had points in this segment:
     PointValuesWriter pointValuesWriter;
 
+    // Non-null if this field ever had vector values in this segment:
+    VectorValuesWriter vectorValuesWriter;
+
     /** We use this to know when a PerField is seen for the
      *  first time in the current document. */
     long fieldGen = -1;

lucene/core/src/java/org/apache/lucene/index/LeafReader.java

@@ -203,6 +203,10 @@ public abstract class LeafReader extends IndexReader {
    *  used by a single thread. */
   public abstract NumericDocValues getNormValues(String field) throws IOException;
 
+  /** Returns {@link VectorValues} for this field, or null if no {@link VectorValues} were indexed.
+   * The returned instance should only be used by a single thread. */
+  public abstract VectorValues getVectorValues(String field) throws IOException;
+
   /**
    * Get the {@link FieldInfos} describing all fields in
    * this reader.

lucene/core/src/java/org/apache/lucene/index/MergeReaderWrapper.java

@@ -194,6 +194,11 @@ class MergeReaderWrapper extends LeafReader {
     return in.getPointValues(fieldName);
   }
 
+  @Override
+  public VectorValues getVectorValues(String fieldName) throws IOException {
+    return in.getVectorValues(fieldName);
+  }
+
   @Override
   public int numDocs() {
     return in.numDocs();

lucene/core/src/java/org/apache/lucene/index/MergeState.java

@@ -24,6 +24,7 @@ import java.util.Locale;
 
 import org.apache.lucene.codecs.DocValuesProducer;
 import org.apache.lucene.codecs.FieldsProducer;
+import org.apache.lucene.codecs.VectorReader;
 import org.apache.lucene.codecs.NormsProducer;
 import org.apache.lucene.codecs.PointsReader;
 import org.apache.lucene.codecs.StoredFieldsReader;
@@ -77,6 +78,9 @@ public class MergeState {
   /** Point readers to merge */
   public final PointsReader[] pointsReaders;
 
+  /** Vector readers to merge */
+  public final VectorReader[] vectorReaders;
+
   /** Max docs per reader */
   public final int[] maxDocs;
 
@@ -103,6 +107,7 @@ public class MergeState {
     termVectorsReaders = new TermVectorsReader[numReaders];
     docValuesProducers = new DocValuesProducer[numReaders];
     pointsReaders = new PointsReader[numReaders];
+    vectorReaders = new VectorReader[numReaders];
     fieldInfos = new FieldInfos[numReaders];
     liveDocs = new Bits[numReaders];
 
@@ -139,6 +144,12 @@ public class MergeState {
       if (pointsReaders[i] != null) {
         pointsReaders[i] = pointsReaders[i].getMergeInstance();
       }
+
+      vectorReaders[i] = reader.getVectorReader();
+      if (vectorReaders[i] != null) {
+        vectorReaders[i] = vectorReaders[i].getMergeInstance();
+      }
+
       numDocs += reader.numDocs();
     }
 

lucene/core/src/java/org/apache/lucene/index/ParallelLeafReader.java

@@ -369,6 +369,13 @@ public class ParallelLeafReader extends LeafReader {
     return reader == null ? null : reader.getPointValues(fieldName);
   }
 
+  @Override
+  public VectorValues getVectorValues(String fieldName) throws IOException {
+    ensureOpen();
+    LeafReader reader = fieldToReader.get(fieldName);
+    return reader == null ? null : reader.getVectorValues(fieldName);
+  }
+
   @Override
   public void checkIntegrity() throws IOException {
     ensureOpen();

lucene/core/src/java/org/apache/lucene/index/ReadersAndUpdates.java

@@ -657,7 +657,8 @@ final class ReadersAndUpdates {
   private FieldInfo cloneFieldInfo(FieldInfo fi, int fieldNumber) {
     return new FieldInfo(fi.name, fieldNumber, fi.hasVectors(), fi.omitsNorms(), fi.hasPayloads(),
         fi.getIndexOptions(), fi.getDocValuesType(), fi.getDocValuesGen(), new HashMap<>(fi.attributes()),
-        fi.getPointDimensionCount(), fi.getPointIndexDimensionCount(), fi.getPointNumBytes(), fi.isSoftDeletesField());
+        fi.getPointDimensionCount(), fi.getPointIndexDimensionCount(), fi.getPointNumBytes(),
+        fi.getVectorDimension(), fi.getVectorScoreFunction(), fi.isSoftDeletesField());
   }
 
   private SegmentReader createNewReaderWithLatestLiveDocs(SegmentReader reader) throws IOException {

lucene/core/src/java/org/apache/lucene/index/SegmentCoreReaders.java

@@ -30,6 +30,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.CompoundDirectory;
 import org.apache.lucene.codecs.FieldsProducer;
+import org.apache.lucene.codecs.VectorReader;
 import org.apache.lucene.codecs.NormsProducer;
 import org.apache.lucene.codecs.PointsReader;
 import org.apache.lucene.codecs.PostingsFormat;
@@ -61,6 +62,7 @@ final class SegmentCoreReaders {
   final StoredFieldsReader fieldsReaderOrig;
   final TermVectorsReader termVectorsReaderOrig;
   final PointsReader pointsReader;
+  final VectorReader vectorReader;
   final CompoundDirectory cfsReader;
   final String segment;
   /** 
@@ -137,6 +139,13 @@ final class SegmentCoreReaders {
       } else {
         pointsReader = null;
       }
+
+      if (coreFieldInfos.hasVectorValues()) {
+        vectorReader = codec.vectorFormat().fieldsReader(segmentReadState);
+      } else {
+        vectorReader = null;
+      }
+
       success = true;
     } catch (EOFException | FileNotFoundException e) {
       throw new CorruptIndexException("Problem reading index from " + dir, dir.toString(), e);
@@ -168,7 +177,7 @@ final class SegmentCoreReaders {
     if (ref.decrementAndGet() == 0) {
       try (Closeable finalizer = this::notifyCoreClosedListeners){
         IOUtils.close(termVectorsLocal, fieldsReaderLocal, fields, termVectorsReaderOrig, fieldsReaderOrig,
-                      cfsReader, normsProducer, pointsReader);
+                      cfsReader, normsProducer, pointsReader, vectorReader);
       }
     }
   }

lucene/core/src/java/org/apache/lucene/index/SegmentMerger.java

@@ -23,6 +23,7 @@ import java.util.List;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.DocValuesConsumer;
 import org.apache.lucene.codecs.FieldsConsumer;
+import org.apache.lucene.codecs.VectorWriter;
 import org.apache.lucene.codecs.NormsConsumer;
 import org.apache.lucene.codecs.NormsProducer;
 import org.apache.lucene.codecs.PointsWriter;
@@ -98,15 +99,8 @@ final class SegmentMerger {
       throw new IllegalStateException("Merge would result in 0 document segment");
     }
     mergeFieldInfos();
-    long t0 = 0;
-    if (mergeState.infoStream.isEnabled("SM")) {
-      t0 = System.nanoTime();
-    }
-    int numMerged = mergeFields();
-    if (mergeState.infoStream.isEnabled("SM")) {
-      long t1 = System.nanoTime();
-      mergeState.infoStream.message("SM", ((t1-t0)/1000000) + " msec to merge stored fields [" + numMerged + " docs]");
-    }
+
+    int numMerged = mergeWithLogging(this::mergeFields, "stored fields");
     assert numMerged == mergeState.segmentInfo.maxDoc(): "numMerged=" + numMerged + " vs mergeState.segmentInfo.maxDoc()=" + mergeState.segmentInfo.maxDoc();
 
     final SegmentWriteState segmentWriteState = new SegmentWriteState(mergeState.infoStream, directory, mergeState.segmentInfo,
@@ -115,77 +109,29 @@ final class SegmentMerger {
         IOContext.READ, segmentWriteState.segmentSuffix);
 
     if (mergeState.mergeFieldInfos.hasNorms()) {
-      if (mergeState.infoStream.isEnabled("SM")) {
-        t0 = System.nanoTime();
-      }
-      mergeNorms(segmentWriteState);
-      if (mergeState.infoStream.isEnabled("SM")) {
-        long t1 = System.nanoTime();
-        mergeState.infoStream.message("SM", ((t1-t0)/1000000) + " msec to merge norms [" + numMerged + " docs]");
-      }
+      mergeWithLogging(() -> mergeNorms(segmentWriteState), "norms", numMerged);
     }
 
-    if (mergeState.infoStream.isEnabled("SM")) {
-      t0 = System.nanoTime();
-    }
-    try (NormsProducer norms = mergeState.mergeFieldInfos.hasNorms()
-        ? codec.normsFormat().normsProducer(segmentReadState)
-        : null) {
-      NormsProducer normsMergeInstance = null;
-      if (norms != null) {
-        // Use the merge instance in order to reuse the same IndexInput for all terms
-        normsMergeInstance = norms.getMergeInstance();
-      }
-      mergeTerms(segmentWriteState, normsMergeInstance);
-    }
-    if (mergeState.infoStream.isEnabled("SM")) {
-      long t1 = System.nanoTime();
-      mergeState.infoStream.message("SM", ((t1-t0)/1000000) + " msec to merge postings [" + numMerged + " docs]");
-    }
+    mergeWithLogging(() -> mergeTerms(segmentWriteState, segmentReadState), "postings", numMerged);
 
-    if (mergeState.infoStream.isEnabled("SM")) {
-      t0 = System.nanoTime();
-    }
     if (mergeState.mergeFieldInfos.hasDocValues()) {
-      mergeDocValues(segmentWriteState);
-    }
-    if (mergeState.infoStream.isEnabled("SM")) {
-      long t1 = System.nanoTime();
-      mergeState.infoStream.message("SM", ((t1-t0)/1000000) + " msec to merge doc values [" + numMerged + " docs]");
+      mergeWithLogging(() -> mergeDocValues(segmentWriteState), "doc values", numMerged);
     }
 
-    if (mergeState.infoStream.isEnabled("SM")) {
-      t0 = System.nanoTime();
-    }
     if (mergeState.mergeFieldInfos.hasPointValues()) {
-      mergePoints(segmentWriteState);
+      mergeWithLogging(() -> mergePoints(segmentWriteState), "points", numMerged);
     }
-    if (mergeState.infoStream.isEnabled("SM")) {
-      long t1 = System.nanoTime();
-      mergeState.infoStream.message("SM", ((t1-t0)/1000000) + " msec to merge points [" + numMerged + " docs]");
+
+    if (mergeState.mergeFieldInfos.hasVectorValues()) {
+        mergeWithLogging(() -> mergeVectorValues(segmentWriteState), "numeric vectors", numMerged);
     }
 
     if (mergeState.mergeFieldInfos.hasVectors()) {
-      if (mergeState.infoStream.isEnabled("SM")) {
-        t0 = System.nanoTime();
-      }
-      numMerged = mergeVectors();
-      if (mergeState.infoStream.isEnabled("SM")) {
-        long t1 = System.nanoTime();
-        mergeState.infoStream.message("SM", ((t1-t0)/1000000) + " msec to merge vectors [" + numMerged + " docs]");
-      }
-      assert numMerged == mergeState.segmentInfo.maxDoc();
+      mergeWithLogging(this::mergeTermVectors, "term vectors");
     }
-    
+
     // write the merged infos
-    if (mergeState.infoStream.isEnabled("SM")) {
-      t0 = System.nanoTime();
-    }
-    codec.fieldInfosFormat().write(directory, mergeState.segmentInfo, "", mergeState.mergeFieldInfos, context);
-    if (mergeState.infoStream.isEnabled("SM")) {
-      long t1 = System.nanoTime();
-      mergeState.infoStream.message("SM", ((t1-t0)/1000000) + " msec to write field infos [" + numMerged + " docs]");
-    }
+    mergeWithLogging(() -> codec.fieldInfosFormat().write(directory, mergeState.segmentInfo, "", mergeState.mergeFieldInfos, context), "field infos", numMerged);
 
     return mergeState;
   }
@@ -207,7 +153,22 @@ final class SegmentMerger {
       consumer.merge(mergeState);
     }
   }
-  
+
+  private void mergeTerms(SegmentWriteState segmentWriteState, SegmentReadState segmentReadState) throws IOException {
+    try (NormsProducer norms = mergeState.mergeFieldInfos.hasNorms()
+        ? codec.normsFormat().normsProducer(segmentReadState)
+        : null) {
+      NormsProducer normsMergeInstance = null;
+      if (norms != null) {
+        // Use the merge instance in order to reuse the same IndexInput for all terms
+        normsMergeInstance = norms.getMergeInstance();
+      }
+      try (FieldsConsumer consumer = codec.postingsFormat().fieldsConsumer(segmentWriteState)) {
+        consumer.merge(mergeState, normsMergeInstance);
+      }
+    }
+  }
+
   public void mergeFieldInfos() {
     for (FieldInfos readerFieldInfos : mergeState.fieldInfos) {
       for (FieldInfo fi : readerFieldInfos) {
@@ -233,15 +194,51 @@ final class SegmentMerger {
    * Merge the TermVectors from each of the segments into the new one.
    * @throws IOException if there is a low-level IO error
    */
-  private int mergeVectors() throws IOException {
+  private int mergeTermVectors() throws IOException {
     try (TermVectorsWriter termVectorsWriter = codec.termVectorsFormat().vectorsWriter(directory, mergeState.segmentInfo, context)) {
-      return termVectorsWriter.merge(mergeState);
+      int numMerged = termVectorsWriter.merge(mergeState);
+      assert numMerged == mergeState.segmentInfo.maxDoc();
+      return numMerged;
     }
   }
 
-  private void mergeTerms(SegmentWriteState segmentWriteState, NormsProducer norms) throws IOException {
-    try (FieldsConsumer consumer = codec.postingsFormat().fieldsConsumer(segmentWriteState)) {
-      consumer.merge(mergeState, norms);
+  private void mergeVectorValues(SegmentWriteState segmentWriteState) throws IOException {
+    try (VectorWriter writer = codec.vectorFormat().fieldsWriter(segmentWriteState)) {
+      writer.merge(mergeState);
     }
   }
+
+  private interface Merger {
+    int merge() throws IOException;
+  }
+
+  private interface VoidMerger {
+    void merge() throws IOException;
+  }
+
+  private int mergeWithLogging(Merger merger, String formatName) throws IOException {
+    long t0 = 0;
+    if (mergeState.infoStream.isEnabled("SM")) {
+      t0 = System.nanoTime();
+    }
+    int numMerged = merger.merge();
+    if (mergeState.infoStream.isEnabled("SM")) {
+      long t1 = System.nanoTime();
+      mergeState.infoStream.message("SM", ((t1 - t0) / 1000000) + " msec to merge vector values [" + numMerged + " docs]");
+    }
+    return numMerged;
+  }
+
+  private void mergeWithLogging(VoidMerger merger, String formatName, int numMerged) throws IOException {
+    long t0 = 0;
+    if (mergeState.infoStream.isEnabled("SM")) {
+      t0 = System.nanoTime();
+    }
+    merger.merge();
+    if (mergeState.infoStream.isEnabled("SM")) {
+      long t1 = System.nanoTime();
+      mergeState.infoStream.message("SM", ((t1 - t0) / 1000000) + " msec to merge vector values [" + numMerged + " docs]");
+    }
+  }
+
 }

lucene/core/src/java/org/apache/lucene/index/SegmentReader.java

@@ -26,6 +26,7 @@ import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.DocValuesProducer;
 import org.apache.lucene.codecs.FieldInfosFormat;
 import org.apache.lucene.codecs.FieldsProducer;
+import org.apache.lucene.codecs.VectorReader;
 import org.apache.lucene.codecs.NormsProducer;
 import org.apache.lucene.codecs.PointsReader;
 import org.apache.lucene.codecs.StoredFieldsReader;
@@ -259,6 +260,11 @@ public final class SegmentReader extends CodecReader {
     return docValuesProducer;
   }
 
+  @Override
+  public VectorReader getVectorReader() {
+    return core.vectorReader;
+  }
+
   @Override
   public FieldsProducer getPostingsReader() {
     ensureOpen();

lucene/core/src/java/org/apache/lucene/index/SlowCodecReaderWrapper.java

@@ -24,6 +24,7 @@ import java.util.Iterator;
 
 import org.apache.lucene.codecs.DocValuesProducer;
 import org.apache.lucene.codecs.FieldsProducer;
+import org.apache.lucene.codecs.VectorReader;
 import org.apache.lucene.codecs.NormsProducer;
 import org.apache.lucene.codecs.PointsReader;
 import org.apache.lucene.codecs.StoredFieldsReader;
@@ -78,6 +79,12 @@ public final class SlowCodecReaderWrapper {
           return readerToDocValuesProducer(reader);
         }
 
+        @Override
+        public VectorReader getVectorReader() {
+          reader.ensureOpen();
+          return readerToVectorReader(reader);
+        }
+
         @Override
         public FieldsProducer getPostingsReader() {
           reader.ensureOpen();
@@ -160,6 +167,29 @@ public final class SlowCodecReaderWrapper {
 
     };
   }
+
+  private static VectorReader readerToVectorReader(LeafReader reader) {
+    return new VectorReader() {
+      @Override
+      public VectorValues getVectorValues(String field) throws IOException {
+        return reader.getVectorValues(field);
+      }
+
+      @Override
+      public void checkIntegrity() {
+        // We already checkIntegrity the entire reader up front
+      }
+
+      @Override
+      public void close() {
+      }
+
+      @Override
+      public long ramBytesUsed() {
+        return 0L;
+      }
+    };
+  }
   
   private static NormsProducer readerToNormsProducer(final LeafReader reader) {
     return new NormsProducer() {

lucene/core/src/java/org/apache/lucene/index/VectorValues.java

@@ -0,0 +1,285 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.index;
+
+import java.io.IOException;
+
+import org.apache.lucene.search.DocIdSetIterator;
+import org.apache.lucene.search.TopDocs;
+import org.apache.lucene.util.BytesRef;
+
+/**
+ * This class provides access to per-document floating point vector values indexed as {@link
+ * org.apache.lucene.document.VectorField}.
+ *
+ * @lucene.experimental
+ */
+public abstract class VectorValues extends DocIdSetIterator {
+
+  /** The maximum length of a vector */
+  public static int MAX_DIMENSIONS = 1024;
+
+  /** Sole constructor */
+  protected VectorValues() {}
+
+  /**
+   * Return the dimension of the vectors
+   */
+  public abstract int dimension();
+
+  /**
+   * TODO: should we use cost() for this? We rely on its always being exactly the number
+   * of documents having a value for this field, which is not guaranteed by the cost() contract,
+   * but in all the implementations so far they are the same.
+   * @return the number of vectors returned by this iterator
+   */
+  public abstract int size();
+
+  /**
+   * Return the score function used to compare these vectors
+   */
+  public abstract ScoreFunction scoreFunction();
+
+  /**
+   * Return the vector value for the current document ID.
+   * It is illegal to call this method when the iterator is not positioned: before advancing, or after failing to advance.
+   * The returned array may be shared across calls, re-used, and modified as the iterator advances.
+   * @return the vector value
+   */
+  public abstract float[] vectorValue() throws IOException;
+
+  /**
+   * Return the binary encoded vector value for the current document ID. These are the bytes
+   * corresponding to the float array return by {@link #vectorValue}.  It is illegal to call this
+   * method when the iterator is not positioned: before advancing, or after failing to advance.  The
+   * returned storage may be shared across calls, re-used and modified as the iterator advances.
+   * @return the binary value
+   */
+  public BytesRef binaryValue() throws IOException {
+    throw new UnsupportedOperationException();
+  }
+
+  /**
+   * Return a random access interface over this iterator's vectors. Calling the RandomAccess methods will
+   * have no effect on the progress of the iteration or the values returned by this iterator. Successive calls
+   * will retrieve independent copies that do not overwrite each others' returned values.
+   */
+  public abstract RandomAccess randomAccess();
+
+  /**
+   * Provides random access to vectors by dense ordinal.
+   *
+   * @lucene.experimental
+   */
+  public interface RandomAccess {
+
+    /**
+     * Return the number of vector values
+     */
+    int size();
+
+    /**
+     * Return the dimension of the returned vector values
+     */
+    int dimension();
+
+    /**
+     * Return the score function used to compare these vectors
+     */
+    ScoreFunction scoreFunction();
+
+    /**
+     * Return the vector value indexed at the given ordinal. The provided floating point array may
+     * be shared and overwritten by subsequent calls to this method and {@link #binaryValue(int)}.
+     * @param targetOrd a valid ordinal, ≥ 0 and < {@link #size()}.
+     */
+    float[] vectorValue(int targetOrd) throws IOException;
+
+    /**
+     * Return the vector indexed at the given ordinal value as an array of bytes in a BytesRef;
+     * these are the bytes corresponding to the float array in IEEE 754 standard encoding, encoded
+     * using little-endian byte order. The provided bytes may be shared and overwritten by subsequent
+     * calls to this method and {@link #vectorValue(int)}.
+     * @param targetOrd a valid ordinal, ≥ 0 and < {@link #size()}.
+     */
+    BytesRef binaryValue(int targetOrd) throws IOException;
+
+    /**
+     * Return the dense ordinal of the document if it has a vector. This ordinal ranges from 0 to the one less than the number
+     * of documents having a vector in this iterator, and it is guaranteed to increase with increasing docid.
+     * @param docId the document whose ordinal is returned
+     * @return the ordinal of the given document, or -1 if the document has no vector value
+     */
+    //int ordinal(int docId);
+
+    /**
+     * Return the k nearest neighbor documents as determined by comparison of their vector values
+     * for this field, to the given vector, by the field's score function. If the score function is
+     * reversed, lower values indicate nearer vectors, otherwise higher scores indicate nearer
+     * vectors. Unlike relevance scores, vector scores may be negative.
+     * @param target the vector-valued query
+     * @param k      the number of docs to return
+     * @param fanout control the accuracy/speed tradeoff - larger values give better recall at higher cost
+     * @return the k nearest neighbor documents, along with their (scoreFunction-specific) scores.
+     */
+    TopDocs search(float[] target, int k, int fanout) throws IOException;
+  }
+
+  /**
+   * Score function. This is used during indexing and searching of the vectors to determine the nearest neighbors.
+   * Score values may be negative. By default high scores indicate nearer documents, unless the function is reversed.
+   */
+  public enum ScoreFunction {
+    /** No distance function is used. Note: {@link VectorValues.RandomAccess#search(float[], int, int)}
+     * is not supported for fields specifying this score function. */
+    NONE,
+
+    /** Euclidean distance */
+    EUCLIDEAN(true) {
+      @Override
+      public float score(float[] v1, float[] v2) {
+        assert v1.length == v2.length;
+        float squareSum = 0.0f;
+        int dim = v1.length;
+        for (int i = 0; i < dim; i++) {
+          float diff = v1[i] - v2[i];
+          squareSum += diff * diff;
+        }
+        return squareSum;
+      }
+    },
+
+    /** dot product - note, may be negative; larger values are better */
+    DOT_PRODUCT() {
+      @Override
+      public float score(float[] a, float[] b) {
+        float res = 0f;
+        /*
+         * If length of vector is larger than 8, we use unrolled dot product to accelerate the
+         * calculation.
+         */
+        int i;
+        for (i = 0; i < a.length % 8; i++) {
+            res += b[i] * a[i];
+        }
+        if (a.length < 8) {
+            return res;
+        }
+        float s0 = 0f;
+        float s1 = 0f;
+        float s2 = 0f;
+        float s3 = 0f;
+        float s4 = 0f;
+        float s5 = 0f;
+        float s6 = 0f;
+        float s7 = 0f;
+        for (; i + 7 < a.length; i += 8) {
+            s0 += b[i] * a[i];
+            s1 += b[i + 1] * a[i + 1];
+            s2 += b[i + 2] * a[i + 2];
+            s3 += b[i + 3] * a[i + 3];
+            s4 += b[i + 4] * a[i + 4];
+            s5 += b[i + 5] * a[i + 5];
+            s6 += b[i + 6] * a[i + 6];
+            s7 += b[i + 7] * a[i + 7];
+        }
+        res += s0 + s1 + s2 + s3 + s4 + s5 + s6 + s7;
+        return res;
+      }
+    };
+
+    /** If reversed, smaller values are better */
+    final public boolean reversed;
+
+    ScoreFunction(boolean reversed) {
+      this.reversed = reversed;
+    }
+
+    ScoreFunction() {
+      this(false);
+    }
+
+    /**
+     * Calculates the score between the specified two vectors.
+     */
+    public float score(float[] v1, float[] v2) {
+      throw new UnsupportedOperationException();
+    }
+
+  }
+
+   /**
+   * Calculates a similarity score between the two vectors with specified function.
+   */
+  public static float compare(float[] v1, float[] v2, ScoreFunction scoreFunction) {
+    assert v1.length == v2.length : "attempt to compare vectors of lengths: " + v1.length + " " + v2.length;
+    return scoreFunction.score(v1, v2);
+  }
+
+  /**
+   * Represents the lack of vector values. It is returned by providers that do not
+   * support VectorValues.
+   */
+  public static final VectorValues EMPTY = new VectorValues() {
+
+    @Override
+    public int size() {
+      return 0;
+    }
+
+    @Override
+    public int dimension() {
+      return 0;
+    }
+
+    @Override
+    public ScoreFunction scoreFunction() {
+      return ScoreFunction.NONE;
+    }
+
+    @Override
+    public float[] vectorValue() {
+      throw new IllegalStateException("Attempt to get vectors from EMPTY values (which was not advanced)");
+    }
+
+    @Override
+    public RandomAccess randomAccess() {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public int docID() {
+      throw new IllegalStateException("VectorValues is EMPTY, and not positioned on a doc");
+    }
+
+    @Override
+    public int nextDoc() {
+      return NO_MORE_DOCS;
+    }
+
+    @Override
+    public int advance(int target) {
+      return NO_MORE_DOCS;
+    }
+
+    @Override
+    public long cost() {
+      return 0;
+    }
+  };
+}

lucene/core/src/java/org/apache/lucene/index/VectorValuesWriter.java

@@ -0,0 +1,322 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.index;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.lucene.codecs.VectorWriter;
+import org.apache.lucene.search.DocIdSetIterator;
+import org.apache.lucene.search.TopDocs;
+import org.apache.lucene.util.ArrayUtil;
+import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.Counter;
+import org.apache.lucene.util.RamUsageEstimator;
+
+/** Buffers up pending vector value(s) per doc, then flushes when segment flushes. */
+class VectorValuesWriter {
+
+  private final FieldInfo fieldInfo;
+  private final Counter iwBytesUsed;
+  private final List<float[]> vectors = new ArrayList<>();
+  private final DocsWithFieldSet docsWithField;
+
+  private int lastDocID = -1;
+
+  private long bytesUsed;
+
+  VectorValuesWriter(FieldInfo fieldInfo, Counter iwBytesUsed) {
+    this.fieldInfo = fieldInfo;
+    this.iwBytesUsed = iwBytesUsed;
+    this.docsWithField = new DocsWithFieldSet();
+    this.bytesUsed = docsWithField.ramBytesUsed();
+    if (iwBytesUsed != null) {
+      iwBytesUsed.addAndGet(bytesUsed);
+    }
+  }
+
+  /**
+   * Adds a value for the given document. Only a single value may be added.
+   * @param docID the value is added to this document
+   * @param vectorValue the value to add
+   * @throws IllegalArgumentException if a value has already been added to the given document
+   */
+  public void addValue(int docID, float[] vectorValue) {
+    if (docID == lastDocID) {
+      throw new IllegalArgumentException("VectorValuesField \"" + fieldInfo.name + "\" appears more than once in this document (only one value is allowed per field)");
+    }
+    if (vectorValue.length != fieldInfo.getVectorDimension()) {
+      throw new IllegalArgumentException("Attempt to index a vector of dimension " + vectorValue.length +
+          " but \"" + fieldInfo.name + "\" has dimension " + fieldInfo.getVectorDimension());
+    }
+    assert docID > lastDocID;
+    docsWithField.add(docID);
+    vectors.add(ArrayUtil.copyOfSubArray(vectorValue, 0, vectorValue.length));
+    updateBytesUsed();
+    lastDocID = docID;
+  }
+
+  private void updateBytesUsed() {
+    final long newBytesUsed = docsWithField.ramBytesUsed()
+            + vectors.size() * (RamUsageEstimator.NUM_BYTES_OBJECT_REF + RamUsageEstimator.NUM_BYTES_ARRAY_HEADER)
+            + vectors.size() * vectors.get(0).length * Float.BYTES;
+    if (iwBytesUsed != null) {
+      iwBytesUsed.addAndGet(newBytesUsed - bytesUsed);
+    }
+    bytesUsed = newBytesUsed;
+  }
+
+  /**
+   * Flush this field's values to storage, sorting the values in accordance with sortMap
+   * @param sortMap specifies the order of documents being flushed, or null if they are to be flushed in docid order
+   * @param vectorWriter the Codec's vector writer that handles the actual encoding and I/O
+   * @throws IOException if there is an error writing the field and its values
+   */
+  public void flush(Sorter.DocMap sortMap, VectorWriter vectorWriter) throws IOException {
+    VectorValues vectorValues = new BufferedVectorValues(docsWithField, vectors, fieldInfo.getVectorDimension(), fieldInfo.getVectorScoreFunction());
+    if (sortMap != null) {
+      vectorWriter.writeField(fieldInfo, new SortingVectorValues(vectorValues, sortMap));
+    } else {
+      vectorWriter.writeField(fieldInfo, vectorValues);
+    }
+  }
+
+  private static class SortingVectorValues extends VectorValues {
+
+    private final VectorValues delegate;
+    private final VectorValues.RandomAccess randomAccess;
+    private final int[] docIdOffsets;
+    private final int[] ordMap;
+    private int docId = -1;
+
+    SortingVectorValues(VectorValues delegate, Sorter.DocMap sortMap) throws IOException {
+      this.delegate = delegate;
+      randomAccess = delegate.randomAccess();
+      docIdOffsets = new int[sortMap.size()];
+
+      int offset = 1; // 0 means no vector for this (field, document)
+      int docID;
+      while ((docID = delegate.nextDoc()) != NO_MORE_DOCS) {
+        int newDocID = sortMap.oldToNew(docID);
+        docIdOffsets[newDocID] = offset++;
+      }
+
+      // set up ordMap to map from new dense ordinal to old dense ordinal
+      ordMap = new int[offset - 1];
+      int ord = 0;
+      for (int docIdOffset : docIdOffsets) {
+        if (docIdOffset != 0) {
+          ordMap[ord++] = docIdOffset - 1;
+        }
+      }
+      assert ord == ordMap.length;
+    }
+
+    @Override
+    public int docID() {
+      return docId;
+    }
+
+    @Override
+    public int nextDoc() throws IOException {
+      while (docId < docIdOffsets.length - 1) {
+        ++docId;
+        if (docIdOffsets[docId] != 0) {
+          return docId;
+        }
+      }
+      docId = NO_MORE_DOCS;
+      return docId;
+    }
+
+    @Override
+    public BytesRef binaryValue() throws IOException {
+      return randomAccess.binaryValue(docIdOffsets[docId] - 1);
+    }
+
+    @Override
+    public float[] vectorValue() {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public int dimension() {
+      return delegate.dimension();
+    }
+
+    @Override
+    public int size() {
+      return delegate.size();
+    }
+
+    @Override
+    public ScoreFunction scoreFunction() {
+      return delegate.scoreFunction();
+    }
+
+    @Override
+    public int advance(int target) throws IOException {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public long cost() {
+      return size();
+    }
+
+    @Override
+    public RandomAccess randomAccess() {
+      RandomAccess ra = delegate.randomAccess();
+      return new RandomAccess() {
+
+        @Override
+        public int size() {
+          return delegate.size();
+        }
+
+        @Override
+        public int dimension() {
+          return delegate.dimension();
+        }
+
+        @Override
+        public ScoreFunction scoreFunction() {
+          return delegate.scoreFunction();
+        }
+
+        @Override
+        public float[] vectorValue(int targetOrd) throws IOException {
+          return ra.vectorValue(ordMap[targetOrd]);
+        }
+
+        @Override
+        public BytesRef binaryValue(int targetOrd) {
+          throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public TopDocs search(float[] target, int k, int fanout) {
+          throw new UnsupportedOperationException();
+        }
+      };
+    }
+  }
+
+  private static class BufferedVectorValues extends VectorValues implements VectorValues.RandomAccess {
+
+    final DocsWithFieldSet docsWithField;
+
+    // These are always the vectors of a VectorValuesWriter, which are copied when added to it
+    final List<float[]> vectors;
+    final VectorValues.ScoreFunction scoreFunction;
+    final int dimension;
+
+    final ByteBuffer buffer;
+    final BytesRef binaryValue;
+    final ByteBuffer raBuffer;
+    final BytesRef raBinaryValue;
+
+    DocIdSetIterator docsWithFieldIter;
+    int ord = -1;
+
+    BufferedVectorValues(DocsWithFieldSet docsWithField, List<float[]> vectors, int dimension, VectorValues.ScoreFunction scoreFunction) {
+      this.docsWithField = docsWithField;
+      this.vectors = vectors;
+      this.dimension = dimension;
+      this.scoreFunction = scoreFunction;
+      buffer = ByteBuffer.allocate(dimension * Float.BYTES);
+      binaryValue = new BytesRef(buffer.array());
+      raBuffer = ByteBuffer.allocate(dimension * Float.BYTES);
+      raBinaryValue = new BytesRef(raBuffer.array());
+      docsWithFieldIter = docsWithField.iterator();
+    }
+
+    @Override
+    public RandomAccess randomAccess() {
+      return this;
+    }
+
+    @Override
+    public int dimension() {
+      return dimension;
+    }
+
+    @Override
+    public int size() {
+      return vectors.size();
+    }
+
+    @Override
+    public VectorValues.ScoreFunction scoreFunction() {
+      return scoreFunction;
+    }
+
+    @Override
+    public BytesRef binaryValue() {
+      buffer.asFloatBuffer().put(vectorValue());
+      return binaryValue;
+    }
+
+    @Override
+    public BytesRef binaryValue(int targetOrd) {
+      raBuffer.asFloatBuffer().put(vectors.get(targetOrd));
+      return raBinaryValue;
+    }
+
+    @Override
+    public float[] vectorValue() {
+      return vectors.get(ord);
+    }
+
+    @Override
+    public float[] vectorValue(int targetOrd) {
+      return vectors.get(targetOrd);
+    }
+
+    @Override
+    public int docID() {
+      return docsWithFieldIter.docID();
+    }
+
+    @Override
+    public int nextDoc() throws IOException {
+      int docID = docsWithFieldIter.nextDoc();
+      if (docID != NO_MORE_DOCS) {
+        ++ord;
+      }
+      return docID;
+    }
+
+    @Override
+    public int advance(int target) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public long cost() {
+      return docsWithFieldIter.cost();
+    }
+
+    @Override
+    public TopDocs search(float[] target, int k, int fanout) throws IOException {
+      throw new UnsupportedOperationException();
+    }
+  }
+}

lucene/core/src/resources/META-INF/services/org.apache.lucene.codecs.Codec

@@ -13,4 +13,4 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-org.apache.lucene.codecs.lucene87.Lucene87Codec
+org.apache.lucene.codecs.lucene90.Lucene90Codec

lucene/core/src/test/org/apache/lucene/codecs/lucene87/TestLucene87StoredFieldsFormatHighCompression.java

@@ -19,6 +19,7 @@ package org.apache.lucene.codecs.lucene87;
 
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat.Mode;
+import org.apache.lucene.codecs.lucene90.Lucene90Codec;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.StoredField;
 import org.apache.lucene.index.BaseStoredFieldsFormatTestCase;
@@ -32,7 +33,7 @@ import com.carrotsearch.randomizedtesting.generators.RandomPicks;
 public class TestLucene87StoredFieldsFormatHighCompression extends BaseStoredFieldsFormatTestCase {
   @Override
   protected Codec getCodec() {
-    return new Lucene87Codec(Mode.BEST_COMPRESSION);
+    return new Lucene90Codec(Mode.BEST_COMPRESSION);
   }
   
   /**
@@ -43,7 +44,7 @@ public class TestLucene87StoredFieldsFormatHighCompression extends BaseStoredFie
     Directory dir = newDirectory();
     for (int i = 0; i < 10; i++) {
       IndexWriterConfig iwc = newIndexWriterConfig();
-      iwc.setCodec(new Lucene87Codec(RandomPicks.randomFrom(random(), Mode.values())));
+      iwc.setCodec(new Lucene90Codec(RandomPicks.randomFrom(random(), Mode.values())));
       IndexWriter iw = new IndexWriter(dir, newIndexWriterConfig());
       Document doc = new Document();
       doc.add(new StoredField("field1", "value1"));
@@ -70,7 +71,7 @@ public class TestLucene87StoredFieldsFormatHighCompression extends BaseStoredFie
   
   public void testInvalidOptions() {
     expectThrows(NullPointerException.class, () -> {
-      new Lucene87Codec(null);
+      new Lucene90Codec(null);
     });
 
     expectThrows(NullPointerException.class, () -> {

lucene/core/src/test/org/apache/lucene/index/TestIndexableField.java

@@ -106,6 +106,16 @@ public class TestIndexableField extends LuceneTestCase {
         return 0;
       }
 
+      @Override
+      public int vectorDimension() {
+        return 0;
+      }
+
+      @Override
+      public VectorValues.ScoreFunction vectorScoreFunction() {
+        return VectorValues.ScoreFunction.NONE;
+      }
+
       @Override
       public Map<String, String> getAttributes() {
         return null;

lucene/core/src/test/org/apache/lucene/index/TestPendingSoftDeletes.java

@@ -37,6 +37,8 @@ import org.apache.lucene.util.IOUtils;
 import org.apache.lucene.util.StringHelper;
 import org.apache.lucene.util.Version;
 
+import static org.apache.lucene.index.VectorValues.ScoreFunction.NONE;
+
 public class TestPendingSoftDeletes extends TestPendingDeletes {
 
   @Override
@@ -164,7 +166,7 @@ public class TestPendingSoftDeletes extends TestPendingDeletes {
     deletes.onNewReader(segmentReader, commitInfo);
     reader.close();
     writer.close();
-    FieldInfo fieldInfo = new FieldInfo("_soft_deletes", 1, false, false, false, IndexOptions.NONE, DocValuesType.NUMERIC, 0, Collections.emptyMap(), 0, 0, 0, true);
+    FieldInfo fieldInfo = new FieldInfo("_soft_deletes", 1, false, false, false, IndexOptions.NONE, DocValuesType.NUMERIC, 0, Collections.emptyMap(), 0, 0, 0, 0, NONE, true);
     List<Integer> docsDeleted = Arrays.asList(1, 3, 7, 8, DocIdSetIterator.NO_MORE_DOCS);
     List<DocValuesFieldUpdates> updates = Arrays.asList(singleUpdate(docsDeleted, 10, true));
     for (DocValuesFieldUpdates update : updates) {
@@ -185,7 +187,7 @@ public class TestPendingSoftDeletes extends TestPendingDeletes {
 
     docsDeleted = Arrays.asList(1, 2, DocIdSetIterator.NO_MORE_DOCS);
     updates = Arrays.asList(singleUpdate(docsDeleted, 10, true));
-    fieldInfo = new FieldInfo("_soft_deletes", 1, false, false, false, IndexOptions.NONE, DocValuesType.NUMERIC, 1, Collections.emptyMap(), 0, 0, 0, true);
+    fieldInfo = new FieldInfo("_soft_deletes", 1, false, false, false, IndexOptions.NONE, DocValuesType.NUMERIC, 1, Collections.emptyMap(), 0, 0, 0, 0, NONE, true);
     for (DocValuesFieldUpdates update : updates) {
       deletes.onDocValuesUpdate(fieldInfo, update.iterator());
     }
@@ -228,7 +230,7 @@ public class TestPendingSoftDeletes extends TestPendingDeletes {
     SegmentCommitInfo segmentInfo = segmentReader.getSegmentInfo();
     PendingDeletes deletes = newPendingDeletes(segmentInfo);
     deletes.onNewReader(segmentReader, segmentInfo);
-    FieldInfo fieldInfo = new FieldInfo("_soft_deletes", 1, false, false, false, IndexOptions.NONE, DocValuesType.NUMERIC, segmentInfo.getNextDocValuesGen(), Collections.emptyMap(), 0, 0, 0, true);
+    FieldInfo fieldInfo = new FieldInfo("_soft_deletes", 1, false, false, false, IndexOptions.NONE, DocValuesType.NUMERIC, segmentInfo.getNextDocValuesGen(), Collections.emptyMap(), 0, 0, 0, 0, NONE, true);
     List<Integer> docsDeleted = Arrays.asList(1, DocIdSetIterator.NO_MORE_DOCS);
     List<DocValuesFieldUpdates> updates = Arrays.asList(singleUpdate(docsDeleted, 3, true));
     for (DocValuesFieldUpdates update : updates) {
@@ -276,7 +278,7 @@ public class TestPendingSoftDeletes extends TestPendingDeletes {
     SegmentCommitInfo segmentInfo = segmentReader.getSegmentInfo();
     PendingDeletes deletes = newPendingDeletes(segmentInfo);
     deletes.onNewReader(segmentReader, segmentInfo);
-    FieldInfo fieldInfo = new FieldInfo("_soft_deletes", 1, false, false, false, IndexOptions.NONE, DocValuesType.NUMERIC, segmentInfo.getNextDocValuesGen(), Collections.emptyMap(), 0, 0, 0, true);
+    FieldInfo fieldInfo = new FieldInfo("_soft_deletes", 1, false, false, false, IndexOptions.NONE, DocValuesType.NUMERIC, segmentInfo.getNextDocValuesGen(), Collections.emptyMap(), 0, 0, 0, 0, NONE, true);
     List<DocValuesFieldUpdates> updates = Arrays.asList(singleUpdate(Arrays.asList(0, 1, DocIdSetIterator.NO_MORE_DOCS), 3, false));
     for (DocValuesFieldUpdates update : updates) {
       deletes.onDocValuesUpdate(fieldInfo, update.iterator());
@@ -295,7 +297,7 @@ public class TestPendingSoftDeletes extends TestPendingDeletes {
     assertEquals(0, deletes.numPendingDeletes());
 
     segmentInfo.advanceDocValuesGen();
-    fieldInfo = new FieldInfo("_soft_deletes", 1, false, false, false, IndexOptions.NONE, DocValuesType.NUMERIC, segmentInfo.getNextDocValuesGen(), Collections.emptyMap(), 0, 0, 0, true);
+    fieldInfo = new FieldInfo("_soft_deletes", 1, false, false, false, IndexOptions.NONE, DocValuesType.NUMERIC, segmentInfo.getNextDocValuesGen(), Collections.emptyMap(), 0, 0, 0, 0, NONE, true);
     updates = Arrays.asList(singleUpdate(Arrays.asList(1, DocIdSetIterator.NO_MORE_DOCS), 3, true));
     for (DocValuesFieldUpdates update : updates) {
       deletes.onDocValuesUpdate(fieldInfo, update.iterator());

lucene/core/src/test/org/apache/lucene/index/TestSegmentToThreadMapping.java

@@ -106,6 +106,9 @@ public class TestSegmentToThreadMapping extends LuceneTestCase {
         return null;
       }
 
+      @Override
+      public VectorValues getVectorValues(String field) { return null; }
+
       @Override
       protected void doClose() {
       }

lucene/core/src/test/org/apache/lucene/index/TestVectorValues.java

@@ -0,0 +1,722 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.index;
+
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+
+import org.apache.lucene.codecs.Codec;
+import org.apache.lucene.document.Document;
+import org.apache.lucene.document.Field;
+import org.apache.lucene.document.Field.Store;
+import org.apache.lucene.document.NumericDocValuesField;
+import org.apache.lucene.document.StringField;
+import org.apache.lucene.document.VectorField;
+import org.apache.lucene.index.VectorValues.ScoreFunction;
+import org.apache.lucene.search.Sort;
+import org.apache.lucene.search.SortField;
+import org.apache.lucene.store.Directory;
+import org.apache.lucene.store.FSDirectory;
+import org.apache.lucene.util.IOUtils;
+import org.apache.lucene.util.LuceneTestCase;
+import org.apache.lucene.util.TestUtil;
+
+import static org.apache.lucene.search.DocIdSetIterator.NO_MORE_DOCS;
+
+/** Test Indexing/IndexWriter with vectors */
+public class TestVectorValues extends LuceneTestCase {
+
+  private IndexWriterConfig createIndexWriterConfig() {
+    IndexWriterConfig iwc = newIndexWriterConfig();
+    iwc.setCodec(Codec.forName("Lucene90"));
+    return iwc;
+  }
+
+  // Suddenly add vectors to an existing field:
+  public void testUpgradeFieldToVectors() throws Exception {
+    try (Directory dir = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(newStringField("f", "foo", Store.NO));
+        w.addDocument(doc);
+      }
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+      }
+    }
+  }
+
+  public void testFieldConstructor() {
+    float[] v = new float[1];
+    VectorField field = new VectorField("f", v);
+    assertEquals(1, field.fieldType().vectorDimension());
+    assertEquals(ScoreFunction.EUCLIDEAN, field.fieldType().vectorScoreFunction());
+    assertSame(v, field.vectorValue());
+  }
+
+  public void testFieldConstructorExceptions() {
+    expectThrows(IllegalArgumentException.class, () -> new VectorField(null, new float[1]));
+    expectThrows(IllegalArgumentException.class, () -> new VectorField("f", null));
+    expectThrows(IllegalArgumentException.class, () -> new VectorField("f", new float[1], null));
+    expectThrows(IllegalArgumentException.class, () -> new VectorField("f", new float[0]));
+    expectThrows(IllegalArgumentException.class, () -> new VectorField("f", new float[VectorValues.MAX_DIMENSIONS + 1]));
+  }
+
+  public void testFieldSetValue() {
+    VectorField field = new VectorField("f", new float[1]);
+    float[] v1 = new float[1];
+    field.setVectorValue(v1);
+    assertSame(v1, field.vectorValue());
+    expectThrows(IllegalArgumentException.class, () -> field.setVectorValue(new float[2]));
+    expectThrows(IllegalArgumentException.class, () -> field.setVectorValue(null));
+  }
+
+  // Illegal schema change tests:
+
+  public void testIllegalDimChangeTwoDocs() throws Exception {
+    try (Directory dir = newDirectory();
+         IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+      Document doc = new Document();
+      doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+      w.addDocument(doc);
+      if (random().nextBoolean()) {
+        // sometimes test with two segments
+        w.commit();
+      }
+
+      Document doc2 = new Document();
+      doc2.add(new VectorField("f", new float[3], ScoreFunction.DOT_PRODUCT));
+      IllegalArgumentException expected = expectThrows(IllegalArgumentException.class,
+          () -> w.addDocument(doc2));
+      assertEquals("cannot change vector dimension from 4 to 3 for field=\"f\"", expected.getMessage());
+    }
+  }
+
+  public void testIllegalScoreFunctionChange() throws Exception {
+    try (Directory dir = newDirectory();
+         IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+      Document doc = new Document();
+      doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+      w.addDocument(doc);
+      if (random().nextBoolean()) {
+        // sometimes test with two segments
+        w.commit();
+      }
+
+      Document doc2 = new Document();
+      doc2.add(new VectorField("f", new float[4], ScoreFunction.EUCLIDEAN));
+      IllegalArgumentException expected = expectThrows(IllegalArgumentException.class,
+          () -> w.addDocument(doc2));
+      assertEquals("cannot change vector score function from DOT_PRODUCT to EUCLIDEAN for field=\"f\"", expected.getMessage());
+    }
+  }
+
+  public void testIllegalDimChangeTwoWriters() throws Exception {
+    try (Directory dir = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+      }
+
+      try (IndexWriter w2 = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc2 = new Document();
+        doc2.add(new VectorField("f", new float[1], ScoreFunction.DOT_PRODUCT));
+        IllegalArgumentException expected = expectThrows(IllegalArgumentException.class,
+            () -> w2.addDocument(doc2));
+        assertEquals("cannot change vector dimension from 4 to 1 for field=\"f\"", expected.getMessage());
+      }
+    }
+  }
+
+  public void testIllegalScoreFunctionChangeTwoWriters() throws Exception {
+    try (Directory dir = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+      }
+
+      try (IndexWriter w2 = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc2 = new Document();
+        doc2.add(new VectorField("f", new float[4], ScoreFunction.EUCLIDEAN));
+        IllegalArgumentException expected = expectThrows(IllegalArgumentException.class,
+            () -> w2.addDocument(doc2));
+        assertEquals("cannot change vector score function from DOT_PRODUCT to EUCLIDEAN for field=\"f\"", expected.getMessage());
+      }
+    }
+  }
+
+  public void testAddIndexesDirectory0() throws Exception {
+    String fieldName = "field";
+    Document doc = new Document();
+    doc.add(new VectorField(fieldName, new float[4], ScoreFunction.DOT_PRODUCT));
+    try (Directory dir = newDirectory();
+         Directory dir2 = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        w.addDocument(doc);
+      }
+      try (IndexWriter w2 = new IndexWriter(dir2, createIndexWriterConfig())) {
+        w2.addIndexes(new Directory[]{dir});
+        try (IndexReader reader = w2.getReader()) {
+          LeafReader r = reader.leaves().get(0).reader();
+          VectorValues vectorValues = r.getVectorValues(fieldName);
+          assertEquals(0, vectorValues.nextDoc());
+          assertEquals(0, vectorValues.vectorValue()[0], 0);
+          assertEquals(NO_MORE_DOCS, vectorValues.nextDoc());
+        }
+      }
+    }
+  }
+
+  public void testAddIndexesDirectory1() throws Exception {
+    String fieldName = "field";
+    Document doc = new Document();
+    try (Directory dir = newDirectory();
+         Directory dir2 = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        w.addDocument(doc);
+      }
+      doc.add(new VectorField(fieldName, new float[4], ScoreFunction.DOT_PRODUCT)); 
+      try (IndexWriter w2 = new IndexWriter(dir2, createIndexWriterConfig())) {
+        w2.addDocument(doc);
+        w2.addIndexes(new Directory[]{dir});
+        try (IndexReader reader = w2.getReader()) {
+          LeafReader r = reader.leaves().get(0).reader();
+          VectorValues vectorValues = r.getVectorValues(fieldName);
+          assertEquals(0, vectorValues.nextDoc());
+          assertEquals(0, vectorValues.vectorValue()[0], 0);
+          assertEquals(NO_MORE_DOCS, vectorValues.nextDoc());
+        }
+      }
+    }
+  }
+
+  public void testAddIndexesDirectory01() throws Exception {
+    String fieldName = "field";
+    float[] vector = new float[1];
+    Document doc = new Document();
+    doc.add(new VectorField(fieldName, vector, ScoreFunction.DOT_PRODUCT));
+    try (Directory dir = newDirectory();
+         Directory dir2 = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        w.addDocument(doc);
+      }
+      try (IndexWriter w2 = new IndexWriter(dir2, createIndexWriterConfig())) {
+        vector[0] = 1;
+        w2.addDocument(doc);
+        w2.addIndexes(new Directory[]{dir});
+        w2.forceMerge(1);
+        try (IndexReader reader = w2.getReader()) {
+          LeafReader r = reader.leaves().get(0).reader();
+          VectorValues vectorValues = r.getVectorValues(fieldName);
+          assertEquals(0, vectorValues.nextDoc());
+          assertEquals(1, vectorValues.vectorValue()[0], 0);
+          assertEquals(1, vectorValues.nextDoc());
+          assertEquals(0, vectorValues.vectorValue()[0], 0);
+        }
+      }
+    }
+  }
+
+  public void testIllegalDimChangeViaAddIndexesDirectory() throws Exception {
+    try (Directory dir = newDirectory();
+         Directory dir2 = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+      }
+      try (IndexWriter w2 = new IndexWriter(dir2, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[5], ScoreFunction.DOT_PRODUCT));
+        w2.addDocument(doc);
+        IllegalArgumentException expected = expectThrows(IllegalArgumentException.class,
+            () -> w2.addIndexes(new Directory[]{dir}));
+        assertEquals("cannot change vector dimension from 5 to 4 for field=\"f\"", expected.getMessage());
+      }
+    }
+  }
+
+  public void testIllegalScoreFunctionChangeViaAddIndexesDirectory() throws Exception {
+    try (Directory dir = newDirectory();
+         Directory dir2 = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+      }
+      try (IndexWriter w2 = new IndexWriter(dir2, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.EUCLIDEAN));
+        w2.addDocument(doc);
+        IllegalArgumentException expected = expectThrows(IllegalArgumentException.class,
+            () -> w2.addIndexes(dir));
+        assertEquals("cannot change vector score function from EUCLIDEAN to DOT_PRODUCT for field=\"f\"", expected.getMessage());
+      }
+    }
+  }
+
+  public void testIllegalDimChangeViaAddIndexesCodecReader() throws Exception {
+    try (Directory dir = newDirectory();
+         Directory dir2 = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+      }
+      try (IndexWriter w2 = new IndexWriter(dir2, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[5], ScoreFunction.DOT_PRODUCT));
+        w2.addDocument(doc);
+        try (DirectoryReader r = DirectoryReader.open(dir)) {
+          IllegalArgumentException expected = expectThrows(IllegalArgumentException.class,
+              () -> w2.addIndexes(new CodecReader[]{(CodecReader) getOnlyLeafReader(r)}));
+          assertEquals("cannot change vector dimension from 5 to 4 for field=\"f\"", expected.getMessage());
+        }
+      }
+    }
+  }
+
+  public void testIllegalScoreFunctionChangeViaAddIndexesCodecReader() throws Exception {
+    try (Directory dir = newDirectory();
+         Directory dir2 = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+      }
+      try (IndexWriter w2 = new IndexWriter(dir2, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.EUCLIDEAN));
+        w2.addDocument(doc);
+        try (DirectoryReader r = DirectoryReader.open(dir)) {
+          IllegalArgumentException expected = expectThrows(IllegalArgumentException.class,
+              () -> w2.addIndexes(new CodecReader[]{(CodecReader) getOnlyLeafReader(r)}));
+          assertEquals("cannot change vector score function from EUCLIDEAN to DOT_PRODUCT for field=\"f\"", expected.getMessage());
+        }
+      }
+    }
+  }
+
+  public void testIllegalDimChangeViaAddIndexesSlowCodecReader() throws Exception {
+    try (Directory dir = newDirectory();
+         Directory dir2 = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+      }
+      try (IndexWriter w2 = new IndexWriter(dir2, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[5], ScoreFunction.DOT_PRODUCT));
+        w2.addDocument(doc);
+        try (DirectoryReader r = DirectoryReader.open(dir)) {
+          IllegalArgumentException expected = expectThrows(IllegalArgumentException.class,
+              () -> TestUtil.addIndexesSlowly(w2, r));
+          assertEquals("cannot change vector dimension from 5 to 4 for field=\"f\"", expected.getMessage());
+        }
+      }
+    }
+  }
+
+  public void testIllegalScoreFunctionChangeViaAddIndexesSlowCodecReader() throws Exception {
+    try (Directory dir = newDirectory();
+         Directory dir2 = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+      }
+      try (IndexWriter w2 = new IndexWriter(dir2, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.EUCLIDEAN));
+        w2.addDocument(doc);
+        try (DirectoryReader r = DirectoryReader.open(dir)) {
+          IllegalArgumentException expected = expectThrows(IllegalArgumentException.class,
+              () -> TestUtil.addIndexesSlowly(w2, r));
+          assertEquals("cannot change vector score function from EUCLIDEAN to DOT_PRODUCT for field=\"f\"", expected.getMessage());
+        }
+      }
+    }
+  }
+
+  public void testIllegalMultipleValues() throws Exception {
+    try (Directory dir = newDirectory();
+         IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+      Document doc = new Document();
+      doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+      doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+      IllegalArgumentException expected = expectThrows(IllegalArgumentException.class,
+          () -> w.addDocument(doc));
+      assertEquals("VectorValuesField \"f\" appears more than once in this document (only one value is allowed per field)",
+          expected.getMessage());
+    }
+  }
+
+  public void testIllegalDimensionTooLarge() throws Exception {
+    try (Directory dir = newDirectory();
+         IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+      Document doc = new Document();
+      expectThrows(IllegalArgumentException.class,
+          () -> doc.add(new VectorField("f", new float[VectorValues.MAX_DIMENSIONS + 1], ScoreFunction.DOT_PRODUCT)));
+
+      Document doc2 = new Document();
+      doc2.add(new VectorField("f", new float[1], ScoreFunction.EUCLIDEAN));
+      w.addDocument(doc2);
+    }
+  }
+
+  public void testIllegalEmptyVector() throws Exception {
+    try (Directory dir = newDirectory();
+         IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+      Document doc = new Document();
+      Exception e = expectThrows(IllegalArgumentException.class,
+          () -> doc.add(new VectorField("f", new float[0], ScoreFunction.NONE)));
+      assertEquals("cannot index an empty vector", e.getMessage());
+
+      Document doc2 = new Document();
+      doc2.add(new VectorField("f", new float[1], ScoreFunction.NONE));
+      w.addDocument(doc2);
+    }
+  }
+
+  // Write vectors, one segment with default codec, another with SimpleText, then forceMerge
+  public void testDifferentCodecs1() throws Exception {
+    try (Directory dir = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+      }
+      IndexWriterConfig iwc = newIndexWriterConfig();
+      iwc.setCodec(Codec.forName("SimpleText"));
+      try (IndexWriter w = new IndexWriter(dir, iwc)) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+        w.forceMerge(1);
+      }
+    }
+  }
+
+  // Write vectors, one segment with with SimpleText, another with default codec, then forceMerge
+  public void testDifferentCodecs2() throws Exception {
+    IndexWriterConfig iwc = newIndexWriterConfig();
+    iwc.setCodec(Codec.forName("SimpleText"));
+    try (Directory dir = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, iwc)) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+      }
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("f", new float[4], ScoreFunction.DOT_PRODUCT));
+        w.addDocument(doc);
+        w.forceMerge(1);
+      }
+    }
+  }
+
+  public void testInvalidVectorFieldUsage() {
+    VectorField field = new VectorField("field", new float[2], ScoreFunction.NONE);
+
+    expectThrows(IllegalArgumentException.class, () -> field.setIntValue(14));
+
+    expectThrows(IllegalArgumentException.class, () -> field.setVectorValue(new float[1]));
+
+    assertNull(field.numericValue());
+  }
+
+  public void testDeleteAllVectorDocs() throws Exception {
+    try (Directory dir = newDirectory();
+         IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+      Document doc = new Document();
+      doc.add(new StringField("id", "0", Store.NO));
+      doc.add(new VectorField("v", new float[]{2, 3, 5}, ScoreFunction.DOT_PRODUCT));
+      w.addDocument(doc);
+      w.addDocument(new Document());
+      w.commit();
+
+      try (DirectoryReader r = w.getReader()) {
+        assertNotNull(r.leaves().get(0).reader().getVectorValues("v"));
+      }
+      w.deleteDocuments(new Term("id", "0"));
+      w.forceMerge(1);
+      try (DirectoryReader r = w.getReader()) {
+        assertNull(r.leaves().get(0).reader().getVectorValues("v"));
+      }
+    }
+  }
+
+  public void testVectorFieldMissingFromOneSegment() throws Exception {
+    try (Directory dir = FSDirectory.open(createTempDir());
+         IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+      Document doc = new Document();
+      doc.add(new StringField("id", "0", Store.NO));
+      doc.add(new VectorField("v0", new float[]{2, 3, 5}, ScoreFunction.DOT_PRODUCT));
+      w.addDocument(doc);
+      w.commit();
+
+      doc = new Document();
+      doc.add(new VectorField("v1", new float[]{2, 3, 5}, ScoreFunction.DOT_PRODUCT));
+      w.addDocument(doc);
+      w.forceMerge(1);
+    }
+  }
+
+  public void testSparseVectors() throws Exception {
+    int numDocs = atLeast(1000);
+    int numFields = TestUtil.nextInt(random(), 1, 10);
+    int[] fieldDocCounts = new int[numFields];
+    float[] fieldTotals= new float[numFields];
+    int[] fieldDims = new int[numFields];
+    ScoreFunction[] fieldScoreFunctions = new ScoreFunction[numFields];
+    for (int i = 0; i < numFields; i++) {
+      fieldDims[i] = random().nextInt(20) + 1;
+      fieldScoreFunctions[i] = ScoreFunction.values()[random().nextInt(ScoreFunction.values().length)];
+    }
+    try (Directory dir = newDirectory();
+         RandomIndexWriter w = new RandomIndexWriter(random(), dir, createIndexWriterConfig())) {
+      for (int i = 0; i < numDocs; i++) {
+        Document doc = new Document();
+        for (int field = 0; field < numFields; field++) {
+          String fieldName = "int" + field;
+          if (random().nextInt(100) == 17) {
+            float[] v = randomVector(fieldDims[field]);
+            doc.add(new VectorField(fieldName, v, fieldScoreFunctions[field]));
+            fieldDocCounts[field]++;
+            fieldTotals[field] += v[0];
+          }
+        }
+        w.addDocument(doc);
+      }
+
+      try (IndexReader r = w.getReader()) {
+        for (int field = 0; field < numFields; field++) {
+          int docCount = 0;
+          float checksum = 0;
+          String fieldName = "int" + field;
+          for (LeafReaderContext ctx : r.leaves()) {
+            VectorValues vectors = ctx.reader().getVectorValues(fieldName);
+            if (vectors != null) {
+              docCount += vectors.size();
+              while (vectors.nextDoc() != NO_MORE_DOCS) {
+                checksum += vectors.vectorValue()[0];
+              }
+            }
+          }
+          assertEquals(fieldDocCounts[field], docCount);
+          assertEquals(fieldTotals[field], checksum, 1e-5);
+        }
+      }
+    }
+  }
+
+  public void testIndexedValueNotAliased() throws Exception {
+    // We copy indexed values (as for BinaryDocValues) so the input float[] can be reused across
+    // calls to IndexWriter.addDocument.
+    String fieldName = "field";
+    float[] v = { 0 };
+    try (Directory dir = newDirectory();
+         IndexWriter iw = new IndexWriter(dir, createIndexWriterConfig())) {
+      Document doc1 = new Document();
+      doc1.add(new VectorField(fieldName, v, VectorValues.ScoreFunction.EUCLIDEAN));
+      v[0] = 1;
+      Document doc2 = new Document();
+      doc2.add(new VectorField(fieldName, v, VectorValues.ScoreFunction.EUCLIDEAN));
+      iw.addDocument(doc1);
+      iw.addDocument(doc2);
+      v[0] = 2;
+      Document doc3 = new Document();
+      doc3.add(new VectorField(fieldName, v, VectorValues.ScoreFunction.EUCLIDEAN));
+      iw.addDocument(doc3);
+      try (IndexReader reader = iw.getReader()) {
+        LeafReader r = reader.leaves().get(0).reader();
+        VectorValues vectorValues = r.getVectorValues(fieldName);
+        vectorValues.nextDoc();
+        assertEquals(1, vectorValues.vectorValue()[0], 0);
+        vectorValues.nextDoc();
+        assertEquals(1, vectorValues.vectorValue()[0], 0);
+        vectorValues.nextDoc();
+        assertEquals(2, vectorValues.vectorValue()[0], 0);
+      }
+    }
+  }
+
+  public void testSortedIndex() throws Exception {
+    IndexWriterConfig iwc = createIndexWriterConfig();
+    iwc.setIndexSort(new Sort(new SortField("sortkey", SortField.Type.INT)));
+    String fieldName = "field";
+    try (Directory dir = newDirectory();
+         IndexWriter iw = new IndexWriter(dir, iwc)) {
+      add(iw, fieldName, 1, 1, new float[]{1});
+      add(iw, fieldName, 4, 4, new float[]{4});
+      add(iw, fieldName, 3, 3, null);
+      add(iw, fieldName, 2, 2, new float[]{2});
+      try (IndexReader reader = iw.getReader()) {
+        LeafReader leaf = reader.leaves().get(0).reader();
+
+        VectorValues vectorValues = leaf.getVectorValues(fieldName);
+        assertEquals(1, vectorValues.dimension());
+        assertEquals(3, vectorValues.size());
+        assertEquals("1", leaf.document(vectorValues.nextDoc()).get("id"));
+        assertEquals(1f, vectorValues.vectorValue()[0], 0);
+        assertEquals("2", leaf.document(vectorValues.nextDoc()).get("id"));
+        assertEquals(2f, vectorValues.vectorValue()[0], 0);
+        assertEquals("4", leaf.document(vectorValues.nextDoc()).get("id"));
+        assertEquals(4f, vectorValues.vectorValue()[0], 0);
+        assertEquals(NO_MORE_DOCS, vectorValues.nextDoc());
+
+        VectorValues.RandomAccess ra = vectorValues.randomAccess();
+        assertEquals(1f, ra.vectorValue(0)[0], 0);
+        assertEquals(2f, ra.vectorValue(1)[0], 0);
+        assertEquals(4f, ra.vectorValue(2)[0], 0);
+      }
+    }
+  }
+
+  /**
+   * Index random vectors, sometimes skipping documents, sometimes deleting a document,
+   * sometimes merging, sometimes sorting the index,
+   * and verify that the expected values can be read back consistently.
+   */
+  public void testRandom() throws Exception {
+    IndexWriterConfig iwc = createIndexWriterConfig();
+    if (random().nextBoolean()) {
+      iwc.setIndexSort(new Sort(new SortField("sortkey", SortField.Type.INT)));
+    }
+    String fieldName = "field";
+    try (Directory dir = newDirectory();
+         IndexWriter iw = new IndexWriter(dir, iwc)) {
+      int numDoc = atLeast(100);
+      int dimension = atLeast(10);
+      float[] scratch = new float[dimension];
+      int numValues = 0;
+      float[][] values = new float[numDoc][];
+      for (int i = 0; i < numDoc; i++) {
+        if (random().nextInt(7) != 3) {
+          // usually index a vector value for a doc
+          values[i] = randomVector(dimension);
+          ++numValues;
+        }
+        if (random().nextBoolean() && values[i] != null) {
+          // sometimes use a shared scratch array
+          System.arraycopy(values[i], 0, scratch, 0, scratch.length);
+          add(iw, fieldName, i, scratch);
+        } else {
+          add(iw, fieldName, i, values[i]);
+        }
+        if (random().nextInt(10) == 2) {
+          // sometimes delete a random document
+          int idToDelete = random().nextInt(i + 1);
+          iw.deleteDocuments(new Term("id", Integer.toString(idToDelete)));
+          // and remember that it was deleted
+          if (values[idToDelete] != null) {
+            values[idToDelete] = null;
+            --numValues;
+          }
+        }
+        if (random().nextInt(10) == 3) {
+          iw.commit();
+        }
+      }
+      iw.forceMerge(1);
+      try (IndexReader reader = iw.getReader()) {
+        int valueCount = 0, totalSize = 0;
+        for (LeafReaderContext ctx : reader.leaves()) {
+          VectorValues vectorValues = ctx.reader().getVectorValues(fieldName);
+          if (vectorValues == null) {
+            continue;
+          }
+          totalSize += vectorValues.size();
+          int docId;
+          while ((docId = vectorValues.nextDoc()) != NO_MORE_DOCS) {
+            float[] v = vectorValues.vectorValue();
+            assertEquals(dimension, v.length);
+            String idString = ctx.reader().document(docId).getField("id").stringValue();
+            int id = Integer.parseInt(idString);
+            assertArrayEquals(idString, values[id], v, 0);
+            ++valueCount;
+          }
+        }
+        assertEquals(numValues, valueCount);
+        assertEquals(numValues, totalSize);
+      }
+    }
+  }
+
+  private void add(IndexWriter iw, String field, int id, float[] vector) throws IOException {
+    add(iw, field, id, random().nextInt(100), vector);
+  }
+
+  private void add(IndexWriter iw, String field, int id, int sortkey, float[] vector) throws IOException {
+    Document doc = new Document();
+    if (vector != null) {
+      doc.add(new VectorField(field, vector));
+    }
+    doc.add(new NumericDocValuesField("sortkey", sortkey));
+    doc.add(new StringField("id", Integer.toString(id), Field.Store.YES));
+    iw.addDocument(doc);
+  }
+
+  private float[] randomVector(int dim) {
+    float[] v = new float[dim];
+    for (int i = 0; i < dim; i++) {
+      v[i] = random().nextFloat();
+    }
+    return v;
+  }
+
+  public void testCheckIndexIncludesVectors() throws Exception {
+    try (Directory dir = newDirectory()) {
+      try (IndexWriter w = new IndexWriter(dir, createIndexWriterConfig())) {
+        Document doc = new Document();
+        doc.add(new VectorField("v1", randomVector(3), ScoreFunction.NONE));
+        w.addDocument(doc);
+
+        doc.add(new VectorField("v2", randomVector(3), ScoreFunction.NONE));
+        w.addDocument(doc);
+      }
+
+      ByteArrayOutputStream output = new ByteArrayOutputStream();
+      CheckIndex.Status status = TestUtil.checkIndex(dir, false, true, output);
+      assertEquals(1, status.segmentInfos.size());
+      CheckIndex.Status.SegmentInfoStatus segStatus = status.segmentInfos.get(0);
+      // total 3 vector values were indexed:
+      assertEquals(3, segStatus.vectorValuesStatus.totalVectorValues);
+      // ... across 2 fields:
+      assertEquals(2, segStatus.vectorValuesStatus.totalVectorFields);
+
+      // Make sure CheckIndex in fact declares that it is testing vectors!
+      assertTrue(output.toString(IOUtils.UTF_8).contains("test: vectors..."));
+    }
+  }
+
+  public void testScoreFunctionIdentifiers() throws Exception {
+    // make sure we don't accidentally mess up score function identifiers by re-ordering their enumerators
+    assertEquals(0, ScoreFunction.NONE.ordinal());
+    assertEquals(1, ScoreFunction.EUCLIDEAN.ordinal());
+    assertEquals(2, ScoreFunction.DOT_PRODUCT.ordinal());
+    assertEquals(3, ScoreFunction.values().length);
+  }
+
+}

lucene/core/src/test/org/apache/lucene/util/fst/TestFSTs.java

@@ -854,7 +854,7 @@ public class TestFSTs extends LuceneTestCase {
         System.out.println("TEST: cycle=" + cycle);
       }
       RandomIndexWriter w = new RandomIndexWriter(random(), dir,
-                                                  newIndexWriterConfig(new MockAnalyzer(random())).setOpenMode(IndexWriterConfig.OpenMode.CREATE));
+          newIndexWriterConfig(new MockAnalyzer(random())).setOpenMode(IndexWriterConfig.OpenMode.CREATE));
       Document doc = new Document();
       Field idField = newStringField("id", "", Field.Store.NO);
       doc.add(idField);

lucene/highlighter/src/java/org/apache/lucene/search/highlight/TermVectorLeafReader.java

@@ -35,6 +35,7 @@ import org.apache.lucene.index.SortedNumericDocValues;
 import org.apache.lucene.index.SortedSetDocValues;
 import org.apache.lucene.index.StoredFieldVisitor;
 import org.apache.lucene.index.Terms;
+import org.apache.lucene.index.VectorValues;
 import org.apache.lucene.util.Bits;
 import org.apache.lucene.util.Version;
 
@@ -81,7 +82,7 @@ public class TermVectorLeafReader extends LeafReader {
     }
     FieldInfo fieldInfo = new FieldInfo(field, 0,
                                         true, true, terms.hasPayloads(),
-                                        indexOptions, DocValuesType.NONE, -1, Collections.emptyMap(), 0, 0, 0, false);
+                                        indexOptions, DocValuesType.NONE, -1, Collections.emptyMap(), 0, 0, 0, 0, VectorValues.ScoreFunction.NONE, false);
     fieldInfos = new FieldInfos(new FieldInfo[]{fieldInfo});
   }
 
@@ -139,6 +140,11 @@ public class TermVectorLeafReader extends LeafReader {
     return null;
   }
 
+  @Override
+  public VectorValues getVectorValues(String fieldName) {
+    return null;
+  }
+
   @Override
   public void checkIntegrity() throws IOException {
   }

lucene/memory/src/java/org/apache/lucene/index/memory/MemoryIndex.java

@@ -501,7 +501,8 @@ public class MemoryIndex {
     IndexOptions indexOptions = storeOffsets ? IndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS : IndexOptions.DOCS_AND_FREQS_AND_POSITIONS;
     return new FieldInfo(fieldName, ord, fieldType.storeTermVectors(), fieldType.omitNorms(), storePayloads,
         indexOptions, fieldType.docValuesType(), -1, Collections.emptyMap(),
-        fieldType.pointDimensionCount(), fieldType.pointIndexDimensionCount(), fieldType.pointNumBytes(), false);
+        fieldType.pointDimensionCount(), fieldType.pointIndexDimensionCount(), fieldType.pointNumBytes(),
+        fieldType.vectorDimension(), fieldType.vectorScoreFunction(), false);
   }
 
   private void storePointValues(Info info, BytesRef pointValue) {
@@ -521,6 +522,7 @@ public class MemoryIndex {
           info.fieldInfo.name, info.fieldInfo.number, info.fieldInfo.hasVectors(), info.fieldInfo.hasPayloads(),
           info.fieldInfo.hasPayloads(), info.fieldInfo.getIndexOptions(), docValuesType, -1, info.fieldInfo.attributes(),
           info.fieldInfo.getPointDimensionCount(), info.fieldInfo.getPointIndexDimensionCount(), info.fieldInfo.getPointNumBytes(),
+          info.fieldInfo.getVectorDimension(), info.fieldInfo.getVectorScoreFunction(),
           info.fieldInfo.isSoftDeletesField()
       );
     } else if (existingDocValuesType != docValuesType) {
@@ -1241,6 +1243,11 @@ public class MemoryIndex {
       return new MemoryIndexPointValues(info);
     }
 
+    @Override
+    public VectorValues getVectorValues(String fieldName) {
+      return VectorValues.EMPTY;
+    }
+
     @Override
     public void checkIntegrity() throws IOException {
       // no-op

lucene/suggest/src/test/org/apache/lucene/search/suggest/document/TestSuggestField.java

@@ -39,7 +39,7 @@ import org.apache.lucene.analysis.tokenattributes.PayloadAttribute;
 import org.apache.lucene.analysis.tokenattributes.TypeAttribute;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.PostingsFormat;
-import org.apache.lucene.codecs.lucene87.Lucene87Codec;
+import org.apache.lucene.codecs.lucene90.Lucene90Codec;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.IntPoint;
@@ -887,7 +887,7 @@ public class TestSuggestField extends LuceneTestCase {
   static IndexWriterConfig iwcWithSuggestField(Analyzer analyzer, final Set<String> suggestFields) {
     IndexWriterConfig iwc = newIndexWriterConfig(random(), analyzer);
     iwc.setMergePolicy(newLogMergePolicy());
-    Codec filterCodec = new Lucene87Codec() {
+    Codec filterCodec = new Lucene90Codec() {
       CompletionPostingsFormat.FSTLoadMode fstLoadMode =
           RandomPicks.randomFrom(random(), CompletionPostingsFormat.FSTLoadMode.values());
       PostingsFormat postingsFormat = new Completion84PostingsFormat(fstLoadMode);

lucene/test-framework/src/java/org/apache/lucene/index/BaseIndexFileFormatTestCase.java

@@ -354,7 +354,8 @@ abstract class BaseIndexFileFormatTestCase extends LuceneTestCase {
     FieldInfo proto = oneDocReader.getFieldInfos().fieldInfo("field");
     FieldInfo field = new FieldInfo(proto.name, proto.number, proto.hasVectors(), proto.omitsNorms(), proto.hasPayloads(), 
                                     proto.getIndexOptions(), proto.getDocValuesType(), proto.getDocValuesGen(), new HashMap<>(),
-                                    proto.getPointDimensionCount(), proto.getPointIndexDimensionCount(), proto.getPointNumBytes(), proto.isSoftDeletesField());
+                                    proto.getPointDimensionCount(), proto.getPointIndexDimensionCount(), proto.getPointNumBytes(),
+                                    proto.getVectorDimension(), proto.getVectorScoreFunction(), proto.isSoftDeletesField());
 
     FieldInfos fieldInfos = new FieldInfos(new FieldInfo[] { field } );
 

lucene/test-framework/src/java/org/apache/lucene/index/MismatchedLeafReader.java

@@ -80,6 +80,8 @@ public class MismatchedLeafReader extends FilterLeafReader {
                                         oldInfo.getPointDimensionCount(),      // data dimension count
                                         oldInfo.getPointIndexDimensionCount(),      // index dimension count
                                         oldInfo.getPointNumBytes(),  // dimension numBytes
+                                        oldInfo.getVectorDimension(), // number of dimensions of the field's vector
+                                        oldInfo.getVectorScoreFunction(),      // distance function for calculating similarity of the field's vector
                                         oldInfo.isSoftDeletesField()); // used as soft-deletes field
       shuffled.set(i, newInfo);
     }

lucene/test-framework/src/java/org/apache/lucene/index/RandomPostingsTester.java

@@ -130,7 +130,7 @@ public class RandomPostingsTester {
       fieldInfoArray[fieldUpto] = new FieldInfo(field, fieldUpto, false, false, true,
                                                 IndexOptions.DOCS_AND_FREQS_AND_POSITIONS_AND_OFFSETS,
                                                 DocValuesType.NONE, -1, new HashMap<>(),
-                                                0, 0, 0, false);
+                                                0, 0, 0, 0, VectorValues.ScoreFunction.NONE, false);
       fieldUpto++;
 
       SortedMap<BytesRef,SeedAndOrd> postings = new TreeMap<>();
@@ -651,7 +651,7 @@ public class RandomPostingsTester {
                                                    DocValuesType.NONE,
                                                    -1,
                                                    new HashMap<>(),
-                                                   0, 0, 0, false);
+                                                   0, 0, 0, 0, VectorValues.ScoreFunction.NONE, false);
     }
 
     FieldInfos newFieldInfos = new FieldInfos(newFieldInfoArray);

lucene/test-framework/src/java/org/apache/lucene/search/QueryUtils.java

@@ -35,6 +35,7 @@ import org.apache.lucene.index.SortedNumericDocValues;
 import org.apache.lucene.index.SortedSetDocValues;
 import org.apache.lucene.index.StoredFieldVisitor;
 import org.apache.lucene.index.Terms;
+import org.apache.lucene.index.VectorValues;
 import org.apache.lucene.util.Bits;
 import org.apache.lucene.util.LuceneTestCase;
 import org.apache.lucene.util.Version;
@@ -207,6 +208,11 @@ public class QueryUtils {
         return null;
       }
 
+      @Override
+      public VectorValues getVectorValues(String field) throws IOException {
+        return null;
+      }
+
       @Override
       public FieldInfos getFieldInfos() {
         return FieldInfos.EMPTY;

lucene/test-framework/src/java/org/apache/lucene/util/TestRuleSetupAndRestoreClassEnv.java

@@ -34,7 +34,7 @@ import org.apache.lucene.codecs.asserting.AssertingPostingsFormat;
 import org.apache.lucene.codecs.cheapbastard.CheapBastardCodec;
 import org.apache.lucene.codecs.compressing.CompressingCodec;
 import org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat;
-import org.apache.lucene.codecs.lucene87.Lucene87Codec;
+import org.apache.lucene.codecs.lucene90.Lucene90Codec;
 import org.apache.lucene.codecs.mockrandom.MockRandomPostingsFormat;
 import org.apache.lucene.codecs.simpletext.SimpleTextCodec;
 import org.apache.lucene.index.RandomCodec;
@@ -187,8 +187,8 @@ final class TestRuleSetupAndRestoreClassEnv extends AbstractBeforeAfterRule {
       codec = new AssertingCodec();
     } else if ("Compressing".equals(TEST_CODEC) || ("random".equals(TEST_CODEC) && randomVal == 6 && !shouldAvoidCodec("Compressing"))) {
       codec = CompressingCodec.randomInstance(random);
-    } else if ("Lucene87".equals(TEST_CODEC) || ("random".equals(TEST_CODEC) && randomVal == 5 && !shouldAvoidCodec("Lucene87"))) {
-      codec = new Lucene87Codec(RandomPicks.randomFrom(random, Lucene87StoredFieldsFormat.Mode.values())
+    } else if ("Lucene90".equals(TEST_CODEC) || ("random".equals(TEST_CODEC) && randomVal == 5 && !shouldAvoidCodec("Lucene90"))) {
+      codec = new Lucene90Codec(RandomPicks.randomFrom(random, Lucene87StoredFieldsFormat.Mode.values())
       );
     } else if (!"random".equals(TEST_CODEC)) {
       codec = Codec.forName(TEST_CODEC);

lucene/test-framework/src/java/org/apache/lucene/util/TestUtil.java

@@ -46,6 +46,8 @@ import java.util.regex.PatternSyntaxException;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipInputStream;
 
+import com.carrotsearch.randomizedtesting.generators.RandomNumbers;
+import com.carrotsearch.randomizedtesting.generators.RandomPicks;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.DocValuesFormat;
 import org.apache.lucene.codecs.PostingsFormat;
@@ -54,7 +56,7 @@ import org.apache.lucene.codecs.blockterms.LuceneFixedGap;
 import org.apache.lucene.codecs.blocktreeords.BlockTreeOrdsPostingsFormat;
 import org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat;
 import org.apache.lucene.codecs.lucene84.Lucene84PostingsFormat;
-import org.apache.lucene.codecs.lucene87.Lucene87Codec;
+import org.apache.lucene.codecs.lucene90.Lucene90Codec;
 import org.apache.lucene.codecs.perfield.PerFieldDocValuesFormat;
 import org.apache.lucene.codecs.perfield.PerFieldPostingsFormat;
 import org.apache.lucene.document.BinaryDocValuesField;
@@ -101,9 +103,6 @@ import org.apache.lucene.store.IOContext;
 import org.apache.lucene.store.NoLockFactory;
 import org.junit.Assert;
 
-import com.carrotsearch.randomizedtesting.generators.RandomNumbers;
-import com.carrotsearch.randomizedtesting.generators.RandomPicks;
-
 /**
  * General utility methods for Lucene unit tests. 
  */
@@ -919,7 +918,7 @@ public final class TestUtil {
    * This may be different than {@link Codec#getDefault()} because that is randomized. 
    */
   public static Codec getDefaultCodec() {
-    return new Lucene87Codec();
+    return new Lucene90Codec();
   }
   
   /** 

solr/core/src/java/org/apache/solr/index/SlowCompositeReaderWrapper.java

@@ -276,6 +276,12 @@ public final class SlowCompositeReaderWrapper extends LeafReader {
     return null; // because not supported.  Throw UOE?
   }
 
+  @Override
+  public VectorValues getVectorValues(String field) {
+    ensureOpen();
+    return null; // because not supported.  Throw UOE?
+  }
+
   @Override
   public FieldInfos getFieldInfos() {
     return fieldInfos;

solr/core/src/java/org/apache/solr/schema/SchemaField.java

@@ -26,6 +26,7 @@ import org.apache.lucene.index.DocValuesType;
 import org.apache.lucene.index.IndexOptions;
 import org.apache.lucene.index.IndexableField;
 import org.apache.lucene.index.IndexableFieldType;
+import org.apache.lucene.index.VectorValues;
 import org.apache.lucene.search.SortField;
 import org.apache.solr.common.SolrException;
 import org.apache.solr.common.util.SimpleOrderedMap;
@@ -447,6 +448,16 @@ public final class SchemaField extends FieldProperties implements IndexableField
     return 0;
   }
 
+  @Override
+  public int vectorDimension() {
+    return 0;
+  }
+
+  @Override
+  public VectorValues.ScoreFunction vectorScoreFunction() {
+    return VectorValues.ScoreFunction.NONE;
+  }
+
   @Override
   public Map<String, String> getAttributes() {
     return null;

solr/core/src/java/org/apache/solr/search/CollapsingQParserPlugin.java

@@ -493,6 +493,8 @@ public class CollapsingQParserPlugin extends QParserPlugin {
               fieldInfo.getPointDimensionCount(),
               fieldInfo.getPointIndexDimensionCount(),
               fieldInfo.getPointNumBytes(),
+              fieldInfo.getVectorDimension(),
+              fieldInfo.getVectorScoreFunction(),
               fieldInfo.isSoftDeletesField());
           newInfos.add(f);
         } else {

solr/core/src/java/org/apache/solr/search/Insanity.java

@@ -67,7 +67,8 @@ public class Insanity {
         if (fi.name.equals(insaneField)) {
           filteredInfos.add(new FieldInfo(fi.name, fi.number, fi.hasVectors(), fi.omitsNorms(),
                                           fi.hasPayloads(), fi.getIndexOptions(), DocValuesType.NONE, -1, Collections.emptyMap(),
-                                          fi.getPointDimensionCount(), fi.getPointIndexDimensionCount(), fi.getPointNumBytes(), fi.isSoftDeletesField()));
+                                          fi.getPointDimensionCount(), fi.getPointIndexDimensionCount(), fi.getPointNumBytes(),
+                                          fi.getVectorDimension(), fi.getVectorScoreFunction(), fi.isSoftDeletesField()));
         } else {
           filteredInfos.add(fi);
         }

solr/core/src/java/org/apache/solr/uninverting/UninvertingReader.java

@@ -284,7 +284,8 @@ public class UninvertingReader extends FilterLeafReader {
         wrap = true;
         newFieldInfos.add(new FieldInfo(fi.name, fi.number, fi.hasVectors(), fi.omitsNorms(),
             fi.hasPayloads(), fi.getIndexOptions(), type, fi.getDocValuesGen(), fi.attributes(),
-            fi.getPointDimensionCount(), fi.getPointIndexDimensionCount(), fi.getPointNumBytes(), fi.isSoftDeletesField()));
+            fi.getPointDimensionCount(), fi.getPointIndexDimensionCount(), fi.getPointNumBytes(),
+            fi.getVectorDimension(), fi.getVectorScoreFunction(), fi.isSoftDeletesField()));
       } else {
         newFieldInfos.add(fi);
       }

solr/core/src/test/org/apache/solr/search/TestDocSet.java

@@ -37,6 +37,7 @@ import org.apache.lucene.index.SortedNumericDocValues;
 import org.apache.lucene.index.SortedSetDocValues;
 import org.apache.lucene.index.StoredFieldVisitor;
 import org.apache.lucene.index.Terms;
+import org.apache.lucene.index.VectorValues;
 import org.apache.lucene.search.DocIdSet;
 import org.apache.lucene.search.DocIdSetIterator;
 import org.apache.lucene.search.TotalHits;
@@ -343,6 +344,11 @@ public class TestDocSet extends SolrTestCase {
         return null;
       }
 
+      @Override
+      public VectorValues getVectorValues(String field) {
+        return null;
+      }
+
       @Override
       protected void doClose() {
       }