LUCENE-10502: Use IndexedDISI to store docIds and DirectMonotonicWriter/Reader to handle ordToDoc (#880)

Currently vector's all docs of all fields are fully loaded into memory (for sparse cases).
This happens not only when we do vector search, but also when we open an index to 
load meta info for vector readers.

This patch instead uses IndexedDISI to store docIds and DirectMonotonicWriter/Reader to 
handle  ordToDoc mapping. Benefits are reduced memory usage, and faster loading of 
meta info for vector readers.

lucene/backward-codecs/src/java/module-info.java

@@ -30,6 +30,7 @@ module org.apache.lucene.backward_codecs {
   exports org.apache.lucene.backward_codecs.lucene86;
   exports org.apache.lucene.backward_codecs.lucene87;
   exports org.apache.lucene.backward_codecs.lucene90;
+  exports org.apache.lucene.backward_codecs.lucene91;
   exports org.apache.lucene.backward_codecs.packed;
   exports org.apache.lucene.backward_codecs.store;
 
@@ -39,11 +40,13 @@ module org.apache.lucene.backward_codecs {
       org.apache.lucene.backward_codecs.lucene50.Lucene50PostingsFormat,
       org.apache.lucene.backward_codecs.lucene84.Lucene84PostingsFormat;
   provides org.apache.lucene.codecs.KnnVectorsFormat with
-      org.apache.lucene.backward_codecs.lucene90.Lucene90HnswVectorsFormat;
+      org.apache.lucene.backward_codecs.lucene90.Lucene90HnswVectorsFormat,
+      org.apache.lucene.backward_codecs.lucene91.Lucene91HnswVectorsFormat;
   provides org.apache.lucene.codecs.Codec with
       org.apache.lucene.backward_codecs.lucene80.Lucene80Codec,
       org.apache.lucene.backward_codecs.lucene84.Lucene84Codec,
       org.apache.lucene.backward_codecs.lucene86.Lucene86Codec,
       org.apache.lucene.backward_codecs.lucene87.Lucene87Codec,
-      org.apache.lucene.backward_codecs.lucene90.Lucene90Codec;
+      org.apache.lucene.backward_codecs.lucene90.Lucene90Codec,
+      org.apache.lucene.backward_codecs.lucene91.Lucene91Codec;
 }

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene90/Lucene90HnswGraphBuilder.java

@@ -77,7 +77,8 @@ public final class Lucene90HnswGraphBuilder {
       VectorSimilarityFunction similarityFunction,
       int maxConn,
       int beamWidth,
-      long seed) {
+      long seed)
+      throws IOException {
     vectorValues = vectors.randomAccess();
     buildVectors = vectors.randomAccess();
     this.similarityFunction = Objects.requireNonNull(similarityFunction);

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene91/Lucene91Codec.java

@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene91;
+package org.apache.lucene.backward_codecs.lucene91;
 
 import java.util.Objects;
 import org.apache.lucene.codecs.Codec;
@@ -48,9 +48,6 @@ import org.apache.lucene.codecs.perfield.PerFieldPostingsFormat;
  * Implements the Lucene 9.1 index format
  *
  * <p>If you want to reuse functionality of this codec in another codec, extend {@link FilterCodec}.
- *
- * @see org.apache.lucene.codecs.lucene91 package documentation for file format details.
- * @lucene.experimental
  */
 public class Lucene91Codec extends Codec {
 
@@ -164,7 +161,7 @@ public class Lucene91Codec extends Codec {
   }
 
   @Override
-  public final KnnVectorsFormat knnVectorsFormat() {
+  public KnnVectorsFormat knnVectorsFormat() {
     return knnVectorsFormat;
   }
 

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene91/Lucene91HnswVectorsFormat.java

@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-package org.apache.lucene.codecs.lucene91;
+package org.apache.lucene.backward_codecs.lucene91;
 
 import java.io.IOException;
 import org.apache.lucene.codecs.KnnVectorsFormat;
@@ -82,7 +82,7 @@ import org.apache.lucene.util.hnsw.HnswGraph;
  *
  * @lucene.experimental
  */
-public final class Lucene91HnswVectorsFormat extends KnnVectorsFormat {
+public class Lucene91HnswVectorsFormat extends KnnVectorsFormat {
 
   static final String META_CODEC_NAME = "Lucene91HnswVectorsFormatMeta";
   static final String VECTOR_DATA_CODEC_NAME = "Lucene91HnswVectorsFormatData";
@@ -105,19 +105,21 @@ public final class Lucene91HnswVectorsFormat extends KnnVectorsFormat {
    * Controls how many of the nearest neighbor candidates are connected to the new node. Defaults to
    * {@link Lucene91HnswVectorsFormat#DEFAULT_MAX_CONN}. See {@link HnswGraph} for more details.
    */
-  private final int maxConn;
+  final int maxConn;
 
   /**
    * The number of candidate neighbors to track while searching the graph for each newly inserted
    * node. Defaults to to {@link Lucene91HnswVectorsFormat#DEFAULT_BEAM_WIDTH}. See {@link
    * HnswGraph} for details.
    */
-  private final int beamWidth;
+  final int beamWidth;
 
+  /** A constructor for vectors format with default parameters */
   public Lucene91HnswVectorsFormat() {
     this(DEFAULT_MAX_CONN, DEFAULT_BEAM_WIDTH);
   }
 
+  /** A constructor for vectors format */
   public Lucene91HnswVectorsFormat(int maxConn, int beamWidth) {
     super("Lucene91HnswVectorsFormat");
     this.maxConn = maxConn;
@@ -126,7 +128,7 @@ public final class Lucene91HnswVectorsFormat extends KnnVectorsFormat {
 
   @Override
   public KnnVectorsWriter fieldsWriter(SegmentWriteState state) throws IOException {
-    return new Lucene91HnswVectorsWriter(state, maxConn, beamWidth);
+    throw new UnsupportedOperationException("Old codecs may only be used for reading");
   }
 
   @Override

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene91/Lucene91HnswVectorsReader.java

@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-package org.apache.lucene.codecs.lucene91;
+package org.apache.lucene.backward_codecs.lucene91;
 
 import static org.apache.lucene.search.DocIdSetIterator.NO_MORE_DOCS;
 

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene91/package-info.java

@@ -180,8 +180,8 @@
  *       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>{@link org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsFormat Vector values}. The
- *       vector format stores numeric vectors in a format optimized for random access and
+ *   <li>{@link org.apache.lucene.backward_codecs.lucene91.Lucene91HnswVectorsFormat Vector values}.
+ *       The vector format stores numeric vectors in a format optimized for random access and
  *       computation, supporting high-dimensional nearest-neighbor search.
  * </ul>
  *
@@ -310,7 +310,7 @@
  * <td>Holds indexed points</td>
  * </tr>
  * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsFormat Vector values}</td>
+ * <td>{@link org.apache.lucene.backward_codecs.lucene91.Lucene91HnswVectorsFormat 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>
@@ -417,4 +417,4 @@
  * <code>UInt64</code> values, or better yet, {@link org.apache.lucene.store.DataOutput#writeVInt
  * VInt} values which have no limit. </div>
  */
-package org.apache.lucene.codecs.lucene91;
+package org.apache.lucene.backward_codecs.lucene91;

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

@@ -18,3 +18,4 @@ org.apache.lucene.backward_codecs.lucene84.Lucene84Codec
 org.apache.lucene.backward_codecs.lucene86.Lucene86Codec
 org.apache.lucene.backward_codecs.lucene87.Lucene87Codec
 org.apache.lucene.backward_codecs.lucene90.Lucene90Codec
+org.apache.lucene.backward_codecs.lucene91.Lucene91Codec

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

@@ -14,3 +14,4 @@
 #  limitations under the License.
 
 org.apache.lucene.backward_codecs.lucene90.Lucene90HnswVectorsFormat
+org.apache.lucene.backward_codecs.lucene91.Lucene91HnswVectorsFormat

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene91/Lucene91HnswVectorsWriter.java

@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-package org.apache.lucene.codecs.lucene91;
+package org.apache.lucene.backward_codecs.lucene91;
 
 import static org.apache.lucene.search.DocIdSetIterator.NO_MORE_DOCS;
 

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene91/Lucene91RWCodec.java

@@ -0,0 +1,44 @@
+/*
+ * 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.backward_codecs.lucene91;
+
+import org.apache.lucene.codecs.KnnVectorsFormat;
+import org.apache.lucene.codecs.perfield.PerFieldKnnVectorsFormat;
+
+public class Lucene91RWCodec extends Lucene91Codec {
+
+  private final KnnVectorsFormat defaultKnnVectorsFormat;
+  private final KnnVectorsFormat knnVectorsFormat =
+      new PerFieldKnnVectorsFormat() {
+        @Override
+        public KnnVectorsFormat getKnnVectorsFormatForField(String field) {
+          return defaultKnnVectorsFormat;
+        }
+      };
+
+  public Lucene91RWCodec() {
+    this.defaultKnnVectorsFormat =
+        new Lucene91RWHnswVectorsFormat(
+            Lucene91HnswVectorsFormat.DEFAULT_MAX_CONN,
+            Lucene91HnswVectorsFormat.DEFAULT_BEAM_WIDTH);
+  }
+
+  @Override
+  public KnnVectorsFormat knnVectorsFormat() {
+    return knnVectorsFormat;
+  }
+}

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene91/Lucene91RWHnswVectorsFormat.java

@@ -0,0 +1,43 @@
+/*
+ * 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.backward_codecs.lucene91;
+
+import java.io.IOException;
+import org.apache.lucene.codecs.KnnVectorsWriter;
+import org.apache.lucene.index.SegmentWriteState;
+
+public class Lucene91RWHnswVectorsFormat extends Lucene91HnswVectorsFormat {
+
+  public Lucene91RWHnswVectorsFormat(int maxConn, int beamWidth) {
+    super(maxConn, beamWidth);
+  }
+
+  @Override
+  public KnnVectorsWriter fieldsWriter(SegmentWriteState state) throws IOException {
+    return new Lucene91HnswVectorsWriter(state, maxConn, beamWidth);
+  }
+
+  @Override
+  public String toString() {
+    return "Lucene91RWHnswVectorsFormat(name = Lucene91RWHnswVectorsFormat, maxConn = "
+        + maxConn
+        + ", beamWidth="
+        + beamWidth
+        + ")";
+  }
+}

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene91/TestLucene91HnswVectorsFormat.java

@@ -14,21 +14,20 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene91;
+package org.apache.lucene.backward_codecs.lucene91;
 
 import static com.carrotsearch.randomizedtesting.RandomizedTest.randomIntBetween;
-import static org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsFormat.DEFAULT_BEAM_WIDTH;
-import static org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsFormat.DEFAULT_MAX_CONN;
+import static org.apache.lucene.backward_codecs.lucene91.Lucene91HnswVectorsFormat.DEFAULT_BEAM_WIDTH;
+import static org.apache.lucene.backward_codecs.lucene91.Lucene91HnswVectorsFormat.DEFAULT_MAX_CONN;
 
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.KnnVectorsFormat;
 import org.apache.lucene.tests.index.BaseKnnVectorsFormatTestCase;
-import org.apache.lucene.tests.util.TestUtil;
 
 public class TestLucene91HnswVectorsFormat extends BaseKnnVectorsFormatTestCase {
   @Override
   protected Codec getCodec() {
-    return TestUtil.getDefaultCodec();
+    return new Lucene91RWCodec();
   }
 
   public void testToString() {
@@ -38,11 +37,11 @@ public class TestLucene91HnswVectorsFormat extends BaseKnnVectorsFormatTestCase
         new Lucene91Codec() {
           @Override
           public KnnVectorsFormat getKnnVectorsFormatForField(String field) {
-            return new Lucene91HnswVectorsFormat(maxConn, beamWidth);
+            return new Lucene91RWHnswVectorsFormat(maxConn, beamWidth);
           }
         };
     String expectedString =
-        "Lucene91HnswVectorsFormat(name = Lucene91HnswVectorsFormat, maxConn = "
+        "Lucene91RWHnswVectorsFormat(name = Lucene91RWHnswVectorsFormat, maxConn = "
             + maxConn
             + ", beamWidth="
             + beamWidth

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

@@ -27,7 +27,7 @@ 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.lucene91.Lucene91Codec;
+import org.apache.lucene.codecs.lucene92.Lucene92Codec;
 import org.apache.lucene.index.ConcurrentMergeScheduler;
 import org.apache.lucene.index.IndexCommit;
 import org.apache.lucene.index.IndexDeletionPolicy;
@@ -152,7 +152,7 @@ public class CreateIndexTask extends PerfTask {
       try {
         final PostingsFormat postingsFormatChosen = PostingsFormat.forName(postingsFormat);
         iwConf.setCodec(
-            new Lucene91Codec() {
+            new Lucene92Codec() {
               @Override
               public PostingsFormat getPostingsFormatForField(String field) {
                 return postingsFormatChosen;

lucene/core/src/java/module-info.java

@@ -15,6 +15,9 @@
  * limitations under the License.
  */
 
+import org.apache.lucene.codecs.lucene92.Lucene92Codec;
+import org.apache.lucene.codecs.lucene92.Lucene92HnswVectorsFormat;
+
 /** Lucene Core. */
 @SuppressWarnings("module") // the test framework is compiled after the core...
 module org.apache.lucene.core {
@@ -27,8 +30,8 @@ module org.apache.lucene.core {
   exports org.apache.lucene.analysis.tokenattributes;
   exports org.apache.lucene.codecs;
   exports org.apache.lucene.codecs.compressing;
-  exports org.apache.lucene.codecs.lucene91;
   exports org.apache.lucene.codecs.lucene90;
+  exports org.apache.lucene.codecs.lucene92;
   exports org.apache.lucene.codecs.lucene90.blocktree;
   exports org.apache.lucene.codecs.lucene90.compressing;
   exports org.apache.lucene.codecs.perfield;
@@ -60,11 +63,11 @@ module org.apache.lucene.core {
   provides org.apache.lucene.analysis.TokenizerFactory with
       org.apache.lucene.analysis.standard.StandardTokenizerFactory;
   provides org.apache.lucene.codecs.Codec with
-      org.apache.lucene.codecs.lucene91.Lucene91Codec;
+      Lucene92Codec;
   provides org.apache.lucene.codecs.DocValuesFormat with
       org.apache.lucene.codecs.lucene90.Lucene90DocValuesFormat;
   provides org.apache.lucene.codecs.KnnVectorsFormat with
-      org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsFormat;
+      Lucene92HnswVectorsFormat;
   provides org.apache.lucene.codecs.PostingsFormat with
       org.apache.lucene.codecs.lucene90.Lucene90PostingsFormat;
   provides org.apache.lucene.index.SortFieldProvider with

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

@@ -55,7 +55,7 @@ public abstract class Codec implements NamedSPILoader.NamedSPI {
       return LOADER;
     }
 
-    static Codec defaultCodec = LOADER.lookup("Lucene91");
+    static Codec defaultCodec = LOADER.lookup("Lucene92");
   }
 
   private final String name;

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

@@ -85,7 +85,7 @@ public abstract class KnnVectorsFormat implements NamedSPILoader.NamedSPI {
         @Override
         public KnnVectorsWriter fieldsWriter(SegmentWriteState state) {
           throw new UnsupportedOperationException(
-              "Attempt to write EMPTY VectorValues: maybe you forgot to use codec=Lucene91");
+              "Attempt to write EMPTY VectorValues: maybe you forgot to use codec=Lucene92");
         }
 
         @Override

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

@@ -61,7 +61,8 @@ import org.apache.lucene.util.RoaringDocIdSet;
  * <p>Each int-pair entry consists of 2 logical parts:
  *
  * <p>The first 32 bit int holds the index (number of set bits in the blocks) up to just before the
- * wanted block. The maximum number of set bits is the maximum number of documents, which is < 2^31.
+ * wanted block. The maximum number of set bits is the maximum number of documents, which is less
+ * than 2^31.
  *
  * <p>The next int holds the offset in bytes into the underlying slice. As there is a maximum of
  * 2^16 blocks, it follows that the maximum size of any block must not exceed 2^15 bytes to avoid
@@ -89,7 +90,7 @@ import org.apache.lucene.util.RoaringDocIdSet;
  *
  * @lucene.internal
  */
-final class IndexedDISI extends DocIdSetIterator {
+public final class IndexedDISI extends DocIdSetIterator {
 
   // jump-table time/space trade-offs to consider:
   // The block offsets and the block indexes could be stored in more compressed form with
@@ -185,7 +186,7 @@ final class IndexedDISI extends DocIdSetIterator {
    * @return the number of jump-table entries following the blocks, -1 for no entries. This should
    *     be stored in meta and used when creating an instance of IndexedDISI.
    */
-  static short writeBitSet(DocIdSetIterator it, IndexOutput out, byte denseRankPower)
+  public static short writeBitSet(DocIdSetIterator it, IndexOutput out, byte denseRankPower)
       throws IOException {
     final long origo = out.getFilePointer(); // All jumps are relative to the origo
     if ((denseRankPower < 7 || denseRankPower > 15) && denseRankPower != -1) {
@@ -309,7 +310,7 @@ final class IndexedDISI extends DocIdSetIterator {
    *     #writeBitSet(DocIdSetIterator, IndexOutput, byte)}
    * @param cost normally the number of logical docIDs.
    */
-  IndexedDISI(
+  public IndexedDISI(
       IndexInput in,
       long offset,
       long length,

lucene/core/src/java/org/apache/lucene/codecs/lucene92/Lucene92Codec.java

@@ -0,0 +1,217 @@
+/*
+ * 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.lucene92;
+
+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.KnnVectorsFormat;
+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.lucene90.Lucene90CompoundFormat;
+import org.apache.lucene.codecs.lucene90.Lucene90DocValuesFormat;
+import org.apache.lucene.codecs.lucene90.Lucene90FieldInfosFormat;
+import org.apache.lucene.codecs.lucene90.Lucene90LiveDocsFormat;
+import org.apache.lucene.codecs.lucene90.Lucene90NormsFormat;
+import org.apache.lucene.codecs.lucene90.Lucene90PointsFormat;
+import org.apache.lucene.codecs.lucene90.Lucene90PostingsFormat;
+import org.apache.lucene.codecs.lucene90.Lucene90SegmentInfoFormat;
+import org.apache.lucene.codecs.lucene90.Lucene90StoredFieldsFormat;
+import org.apache.lucene.codecs.lucene90.Lucene90TermVectorsFormat;
+import org.apache.lucene.codecs.perfield.PerFieldDocValuesFormat;
+import org.apache.lucene.codecs.perfield.PerFieldKnnVectorsFormat;
+import org.apache.lucene.codecs.perfield.PerFieldPostingsFormat;
+
+/**
+ * Implements the Lucene 9.2 index format
+ *
+ * <p>If you want to reuse functionality of this codec in another codec, extend {@link FilterCodec}.
+ *
+ * @see org.apache.lucene.codecs.lucene92 package documentation for file format details.
+ * @lucene.experimental
+ */
+public class Lucene92Codec extends Codec {
+
+  /** Configuration option for the codec. */
+  public enum Mode {
+    /** Trade compression ratio for retrieval speed. */
+    BEST_SPEED(Lucene90StoredFieldsFormat.Mode.BEST_SPEED),
+    /** Trade retrieval speed for compression ratio. */
+    BEST_COMPRESSION(Lucene90StoredFieldsFormat.Mode.BEST_COMPRESSION);
+
+    private final Lucene90StoredFieldsFormat.Mode storedMode;
+
+    private Mode(Lucene90StoredFieldsFormat.Mode storedMode) {
+      this.storedMode = Objects.requireNonNull(storedMode);
+    }
+  }
+
+  private final TermVectorsFormat vectorsFormat = new Lucene90TermVectorsFormat();
+  private final FieldInfosFormat fieldInfosFormat = new Lucene90FieldInfosFormat();
+  private final SegmentInfoFormat segmentInfosFormat = new Lucene90SegmentInfoFormat();
+  private final LiveDocsFormat liveDocsFormat = new Lucene90LiveDocsFormat();
+  private final CompoundFormat compoundFormat = new Lucene90CompoundFormat();
+  private final NormsFormat normsFormat = new Lucene90NormsFormat();
+
+  private final PostingsFormat defaultPostingsFormat;
+  private final PostingsFormat postingsFormat =
+      new PerFieldPostingsFormat() {
+        @Override
+        public PostingsFormat getPostingsFormatForField(String field) {
+          return Lucene92Codec.this.getPostingsFormatForField(field);
+        }
+      };
+
+  private final DocValuesFormat defaultDVFormat;
+  private final DocValuesFormat docValuesFormat =
+      new PerFieldDocValuesFormat() {
+        @Override
+        public DocValuesFormat getDocValuesFormatForField(String field) {
+          return Lucene92Codec.this.getDocValuesFormatForField(field);
+        }
+      };
+
+  private final KnnVectorsFormat defaultKnnVectorsFormat;
+  private final KnnVectorsFormat knnVectorsFormat =
+      new PerFieldKnnVectorsFormat() {
+        @Override
+        public KnnVectorsFormat getKnnVectorsFormatForField(String field) {
+          return Lucene92Codec.this.getKnnVectorsFormatForField(field);
+        }
+      };
+
+  private final StoredFieldsFormat storedFieldsFormat;
+
+  /** Instantiates a new codec. */
+  public Lucene92Codec() {
+    this(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 Lucene92Codec(Mode mode) {
+    super("Lucene92");
+    this.storedFieldsFormat =
+        new Lucene90StoredFieldsFormat(Objects.requireNonNull(mode).storedMode);
+    this.defaultPostingsFormat = new Lucene90PostingsFormat();
+    this.defaultDVFormat = new Lucene90DocValuesFormat();
+    this.defaultKnnVectorsFormat = new Lucene92HnswVectorsFormat();
+  }
+
+  @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 Lucene90PointsFormat();
+  }
+
+  @Override
+  public final KnnVectorsFormat knnVectorsFormat() {
+    return knnVectorsFormat;
+  }
+
+  /**
+   * Returns the postings format that should be used for writing new segments of <code>field</code>.
+   *
+   * <p>The default implementation always returns "Lucene90".
+   *
+   * <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 defaultPostingsFormat;
+  }
+
+  /**
+   * Returns the docvalues format that should be used for writing new segments of <code>field</code>
+   * .
+   *
+   * <p>The default implementation always returns "Lucene90".
+   *
+   * <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;
+  }
+
+  /**
+   * Returns the vectors format that should be used for writing new segments of <code>field</code>
+   *
+   * <p>The default implementation always returns "lucene92".
+   *
+   * <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 KnnVectorsFormat getKnnVectorsFormatForField(String field) {
+    return defaultKnnVectorsFormat;
+  }
+
+  @Override
+  public final DocValuesFormat docValuesFormat() {
+    return docValuesFormat;
+  }
+
+  @Override
+  public final NormsFormat normsFormat() {
+    return normsFormat;
+  }
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene92/Lucene92HnswVectorsFormat.java

@@ -0,0 +1,160 @@
+/*
+ * 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.lucene92;
+
+import java.io.IOException;
+import org.apache.lucene.codecs.KnnVectorsFormat;
+import org.apache.lucene.codecs.KnnVectorsReader;
+import org.apache.lucene.codecs.KnnVectorsWriter;
+import org.apache.lucene.codecs.lucene90.IndexedDISI;
+import org.apache.lucene.index.SegmentReadState;
+import org.apache.lucene.index.SegmentWriteState;
+import org.apache.lucene.search.DocIdSetIterator;
+import org.apache.lucene.store.IndexOutput;
+import org.apache.lucene.util.hnsw.HnswGraph;
+
+/**
+ * Lucene 9.2 vector format, which encodes numeric vector values and an optional associated graph
+ * connecting the documents having values. The graph is used to power HNSW search. The format
+ * consists of three files:
+ *
+ * <h2>.vec (vector data) file</h2>
+ *
+ * <p>For each field:
+ *
+ * <ul>
+ *   <li>Floating-point vector data ordered by field, document ordinal, and vector dimension. The
+ *       floats are stored in little-endian byte order
+ *   <li>DocIds encoded by {@link IndexedDISI#writeBitSet(DocIdSetIterator, IndexOutput, byte)},
+ *       note that only in sparse case
+ *   <li>OrdToDoc was encoded by {@link org.apache.lucene.util.packed.DirectMonotonicWriter}, note
+ *       that only in sparse case
+ * </ul>
+ *
+ * <h2>.vex (vector index)</h2>
+ *
+ * <p>Stores graphs connecting the documents for each field organized as a list of nodes' neighbours
+ * as following:
+ *
+ * <ul>
+ *   <li>For each level:
+ *       <ul>
+ *         <li>For each node:
+ *             <ul>
+ *               <li><b>[int32]</b> the number of neighbor nodes
+ *               <li><b>array[int32]</b> the neighbor ordinals
+ *               <li><b>array[int32]</b> padding from empty integers if the number of neighbors less
+ *                   than the maximum number of connections (maxConn). Padding is equal to
+ *                   ((maxConn-the number of neighbours) * 4) bytes.
+ *             </ul>
+ *       </ul>
+ * </ul>
+ *
+ * <h2>.vem (vector metadata) file</h2>
+ *
+ * <p>For each field:
+ *
+ * <ul>
+ *   <li><b>[int32]</b> field number
+ *   <li><b>[int32]</b> vector similarity function ordinal
+ *   <li><b>[vlong]</b> offset to this field's vectors in the .vec file
+ *   <li><b>[vlong]</b> length of this field's vectors, in bytes
+ *   <li><b>[vlong]</b> offset to this field's index in the .vex file
+ *   <li><b>[vlong]</b> length of this field's index data, in bytes
+ *   <li><b>[int]</b> dimension of this field's vectors
+ *   <li><b>[int]</b> the number of documents having values for this field
+ *   <li><b>[int8]</b> if equals to -1, dense – all documents have values for a field. If equals to
+ *       0, sparse – some documents missing values.
+ *   <li>DocIds were encoded by {@link IndexedDISI#writeBitSet(DocIdSetIterator, IndexOutput, byte)}
+ *   <li>OrdToDoc was encoded by {@link org.apache.lucene.util.packed.DirectMonotonicWriter}, note
+ *       that only in sparse case
+ *   <li><b>[int]</b> the maximum number of connections (neigbours) that each node can have
+ *   <li><b>[int]</b> number of levels in the graph
+ *   <li>Graph nodes by level. For each level
+ *       <ul>
+ *         <li><b>[int]</b> the number of nodes on this level
+ *         <li><b>array[int]</b> for levels greater than 0 list of nodes on this level, stored as
+ *             the the level 0th nodes ordinals.
+ *       </ul>
+ * </ul>
+ *
+ * @lucene.experimental
+ */
+public final class Lucene92HnswVectorsFormat extends KnnVectorsFormat {
+
+  static final String META_CODEC_NAME = "lucene92HnswVectorsFormatMeta";
+  static final String VECTOR_DATA_CODEC_NAME = "lucene92HnswVectorsFormatData";
+  static final String VECTOR_INDEX_CODEC_NAME = "lucene92HnswVectorsFormatIndex";
+  static final String META_EXTENSION = "vem";
+  static final String VECTOR_DATA_EXTENSION = "vec";
+  static final String VECTOR_INDEX_EXTENSION = "vex";
+
+  static final int VERSION_START = 0;
+  static final int VERSION_CURRENT = VERSION_START;
+
+  /** Default number of maximum connections per node */
+  public static final int DEFAULT_MAX_CONN = 16;
+  /**
+   * Default number of the size of the queue maintained while searching during a graph construction.
+   */
+  public static final int DEFAULT_BEAM_WIDTH = 100;
+
+  static final int DIRECT_MONOTONIC_BLOCK_SHIFT = 16;
+
+  /**
+   * Controls how many of the nearest neighbor candidates are connected to the new node. Defaults to
+   * {@link Lucene92HnswVectorsFormat#DEFAULT_MAX_CONN}. See {@link HnswGraph} for more details.
+   */
+  private final int maxConn;
+
+  /**
+   * The number of candidate neighbors to track while searching the graph for each newly inserted
+   * node. Defaults to to {@link Lucene92HnswVectorsFormat#DEFAULT_BEAM_WIDTH}. See {@link
+   * HnswGraph} for details.
+   */
+  private final int beamWidth;
+
+  public Lucene92HnswVectorsFormat() {
+    this(DEFAULT_MAX_CONN, DEFAULT_BEAM_WIDTH);
+  }
+
+  public Lucene92HnswVectorsFormat(int maxConn, int beamWidth) {
+    super("lucene92HnswVectorsFormat");
+    this.maxConn = maxConn;
+    this.beamWidth = beamWidth;
+  }
+
+  @Override
+  public KnnVectorsWriter fieldsWriter(SegmentWriteState state) throws IOException {
+    return new Lucene92HnswVectorsWriter(state, maxConn, beamWidth);
+  }
+
+  @Override
+  public KnnVectorsReader fieldsReader(SegmentReadState state) throws IOException {
+    return new Lucene92HnswVectorsReader(state);
+  }
+
+  @Override
+  public String toString() {
+    return "lucene92HnswVectorsFormat(name = lucene92HnswVectorsFormat, maxConn = "
+        + maxConn
+        + ", beamWidth="
+        + beamWidth
+        + ")";
+  }
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene92/Lucene92HnswVectorsReader.java

@@ -0,0 +1,449 @@
+/*
+ * 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.lucene92;
+
+import static org.apache.lucene.search.DocIdSetIterator.NO_MORE_DOCS;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+import org.apache.lucene.codecs.CodecUtil;
+import org.apache.lucene.codecs.KnnVectorsReader;
+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.VectorSimilarityFunction;
+import org.apache.lucene.index.VectorValues;
+import org.apache.lucene.search.ScoreDoc;
+import org.apache.lucene.search.TopDocs;
+import org.apache.lucene.search.TotalHits;
+import org.apache.lucene.store.ChecksumIndexInput;
+import org.apache.lucene.store.DataInput;
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.util.Bits;
+import org.apache.lucene.util.IOUtils;
+import org.apache.lucene.util.RamUsageEstimator;
+import org.apache.lucene.util.hnsw.HnswGraph;
+import org.apache.lucene.util.hnsw.HnswGraphSearcher;
+import org.apache.lucene.util.hnsw.NeighborQueue;
+import org.apache.lucene.util.packed.DirectMonotonicReader;
+
+/**
+ * Reads vectors from the index segments along with index data structures supporting KNN search.
+ *
+ * @lucene.experimental
+ */
+public final class Lucene92HnswVectorsReader extends KnnVectorsReader {
+
+  private final FieldInfos fieldInfos;
+  private final Map<String, FieldEntry> fields = new HashMap<>();
+  private final IndexInput vectorData;
+  private final IndexInput vectorIndex;
+
+  Lucene92HnswVectorsReader(SegmentReadState state) throws IOException {
+    this.fieldInfos = state.fieldInfos;
+    int versionMeta = readMetadata(state);
+    boolean success = false;
+    try {
+      vectorData =
+          openDataInput(
+              state,
+              versionMeta,
+              Lucene92HnswVectorsFormat.VECTOR_DATA_EXTENSION,
+              Lucene92HnswVectorsFormat.VECTOR_DATA_CODEC_NAME);
+      vectorIndex =
+          openDataInput(
+              state,
+              versionMeta,
+              Lucene92HnswVectorsFormat.VECTOR_INDEX_EXTENSION,
+              Lucene92HnswVectorsFormat.VECTOR_INDEX_CODEC_NAME);
+      success = true;
+    } finally {
+      if (success == false) {
+        IOUtils.closeWhileHandlingException(this);
+      }
+    }
+  }
+
+  private int readMetadata(SegmentReadState state) throws IOException {
+    String metaFileName =
+        IndexFileNames.segmentFileName(
+            state.segmentInfo.name, state.segmentSuffix, Lucene92HnswVectorsFormat.META_EXTENSION);
+    int versionMeta = -1;
+    try (ChecksumIndexInput meta = state.directory.openChecksumInput(metaFileName, state.context)) {
+      Throwable priorE = null;
+      try {
+        versionMeta =
+            CodecUtil.checkIndexHeader(
+                meta,
+                Lucene92HnswVectorsFormat.META_CODEC_NAME,
+                Lucene92HnswVectorsFormat.VERSION_START,
+                Lucene92HnswVectorsFormat.VERSION_CURRENT,
+                state.segmentInfo.getId(),
+                state.segmentSuffix);
+        readFields(meta, state.fieldInfos);
+      } catch (Throwable exception) {
+        priorE = exception;
+      } finally {
+        CodecUtil.checkFooter(meta, priorE);
+      }
+    }
+    return versionMeta;
+  }
+
+  private static IndexInput openDataInput(
+      SegmentReadState state, int versionMeta, String fileExtension, String codecName)
+      throws IOException {
+    String fileName =
+        IndexFileNames.segmentFileName(state.segmentInfo.name, state.segmentSuffix, fileExtension);
+    IndexInput in = state.directory.openInput(fileName, state.context);
+    int versionVectorData =
+        CodecUtil.checkIndexHeader(
+            in,
+            codecName,
+            Lucene92HnswVectorsFormat.VERSION_START,
+            Lucene92HnswVectorsFormat.VERSION_CURRENT,
+            state.segmentInfo.getId(),
+            state.segmentSuffix);
+    if (versionMeta != versionVectorData) {
+      throw new CorruptIndexException(
+          "Format versions mismatch: meta="
+              + versionMeta
+              + ", "
+              + codecName
+              + "="
+              + versionVectorData,
+          in);
+    }
+    CodecUtil.retrieveChecksum(in);
+    return in;
+  }
+
+  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);
+      }
+      FieldEntry fieldEntry = readField(meta);
+      validateFieldEntry(info, fieldEntry);
+      fields.put(info.name, fieldEntry);
+    }
+  }
+
+  private void validateFieldEntry(FieldInfo info, FieldEntry fieldEntry) {
+    int dimension = info.getVectorDimension();
+    if (dimension != fieldEntry.dimension) {
+      throw new IllegalStateException(
+          "Inconsistent vector dimension for field=\""
+              + info.name
+              + "\"; "
+              + 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);
+    }
+  }
+
+  private VectorSimilarityFunction readSimilarityFunction(DataInput input) throws IOException {
+    int similarityFunctionId = input.readInt();
+    if (similarityFunctionId < 0
+        || similarityFunctionId >= VectorSimilarityFunction.values().length) {
+      throw new CorruptIndexException(
+          "Invalid similarity function id: " + similarityFunctionId, input);
+    }
+    return VectorSimilarityFunction.values()[similarityFunctionId];
+  }
+
+  private FieldEntry readField(IndexInput input) throws IOException {
+    VectorSimilarityFunction similarityFunction = readSimilarityFunction(input);
+    return new FieldEntry(input, similarityFunction);
+  }
+
+  @Override
+  public long ramBytesUsed() {
+    long totalBytes = RamUsageEstimator.shallowSizeOfInstance(Lucene92HnswVectorsFormat.class);
+    totalBytes +=
+        RamUsageEstimator.sizeOfMap(
+            fields, RamUsageEstimator.shallowSizeOfInstance(FieldEntry.class));
+    return totalBytes;
+  }
+
+  @Override
+  public void checkIntegrity() throws IOException {
+    CodecUtil.checksumEntireFile(vectorData);
+    CodecUtil.checksumEntireFile(vectorIndex);
+  }
+
+  @Override
+  public VectorValues getVectorValues(String field) throws IOException {
+    FieldEntry fieldEntry = fields.get(field);
+    return OffHeapVectorValues.load(fieldEntry, vectorData);
+  }
+
+  @Override
+  public TopDocs search(String field, float[] target, int k, Bits acceptDocs, int visitedLimit)
+      throws IOException {
+    FieldEntry fieldEntry = fields.get(field);
+
+    if (fieldEntry.size() == 0) {
+      return new TopDocs(new TotalHits(0, TotalHits.Relation.EQUAL_TO), new ScoreDoc[0]);
+    }
+
+    // bound k by total number of vectors to prevent oversizing data structures
+    k = Math.min(k, fieldEntry.size());
+    OffHeapVectorValues vectorValues = OffHeapVectorValues.load(fieldEntry, vectorData);
+
+    NeighborQueue results =
+        HnswGraphSearcher.search(
+            target,
+            k,
+            vectorValues,
+            fieldEntry.similarityFunction,
+            getGraph(fieldEntry),
+            vectorValues.getAcceptOrds(acceptDocs),
+            visitedLimit);
+
+    int i = 0;
+    ScoreDoc[] scoreDocs = new ScoreDoc[Math.min(results.size(), k)];
+    while (results.size() > 0) {
+      int node = results.topNode();
+      float score = fieldEntry.similarityFunction.convertToScore(results.topScore());
+      results.pop();
+      scoreDocs[scoreDocs.length - ++i] = new ScoreDoc(vectorValues.ordToDoc(node), score);
+    }
+
+    TotalHits.Relation relation =
+        results.incomplete()
+            ? TotalHits.Relation.GREATER_THAN_OR_EQUAL_TO
+            : TotalHits.Relation.EQUAL_TO;
+    return new TopDocs(new TotalHits(results.visitedCount(), relation), scoreDocs);
+  }
+
+  /** Get knn graph values; used for testing */
+  public HnswGraph getGraph(String field) throws IOException {
+    FieldInfo info = fieldInfos.fieldInfo(field);
+    if (info == null) {
+      throw new IllegalArgumentException("No such field '" + field + "'");
+    }
+    FieldEntry entry = fields.get(field);
+    if (entry != null && entry.vectorIndexLength > 0) {
+      return getGraph(entry);
+    } else {
+      return HnswGraph.EMPTY;
+    }
+  }
+
+  private HnswGraph getGraph(FieldEntry entry) throws IOException {
+    IndexInput bytesSlice =
+        vectorIndex.slice("graph-data", entry.vectorIndexOffset, entry.vectorIndexLength);
+    return new OffHeapHnswGraph(entry, bytesSlice);
+  }
+
+  @Override
+  public void close() throws IOException {
+    IOUtils.close(vectorData, vectorIndex);
+  }
+
+  static class FieldEntry {
+
+    final VectorSimilarityFunction similarityFunction;
+    final long vectorDataOffset;
+    final long vectorDataLength;
+    final long vectorIndexOffset;
+    final long vectorIndexLength;
+    final int maxConn;
+    final int numLevels;
+    final int dimension;
+    final int size;
+    final int[][] nodesByLevel;
+    // for each level the start offsets in vectorIndex file from where to read neighbours
+    final long[] graphOffsetsByLevel;
+
+    // the following four variables used to read docIds encoded by IndexDISI
+    // special values of docsWithFieldOffset are -1 and -2
+    // -1 : dense
+    // -2 : empty
+    // other: sparse
+    final long docsWithFieldOffset;
+    final long docsWithFieldLength;
+    final short jumpTableEntryCount;
+    final byte denseRankPower;
+
+    // the following four variables used to read ordToDoc encoded by DirectMonotonicWriter
+    // note that only spare case needs to store ordToDoc
+    final long addressesOffset;
+    final int blockShift;
+    final DirectMonotonicReader.Meta meta;
+    final long addressesLength;
+
+    FieldEntry(IndexInput input, VectorSimilarityFunction similarityFunction) throws IOException {
+      this.similarityFunction = similarityFunction;
+      vectorDataOffset = input.readVLong();
+      vectorDataLength = input.readVLong();
+      vectorIndexOffset = input.readVLong();
+      vectorIndexLength = input.readVLong();
+      dimension = input.readInt();
+      size = input.readInt();
+
+      docsWithFieldOffset = input.readLong();
+      docsWithFieldLength = input.readLong();
+      jumpTableEntryCount = input.readShort();
+      denseRankPower = input.readByte();
+
+      // dense or empty
+      if (docsWithFieldOffset == -1 || docsWithFieldOffset == -2) {
+        addressesOffset = 0;
+        blockShift = 0;
+        meta = null;
+        addressesLength = 0;
+      } else {
+        // sparse
+        addressesOffset = input.readLong();
+        blockShift = input.readVInt();
+        meta = DirectMonotonicReader.loadMeta(input, size, blockShift);
+        addressesLength = input.readLong();
+      }
+
+      // read nodes by level
+      maxConn = input.readInt();
+      numLevels = input.readInt();
+      nodesByLevel = new int[numLevels][];
+      for (int level = 0; level < numLevels; level++) {
+        int numNodesOnLevel = input.readInt();
+        if (level == 0) {
+          // we don't store nodes for level 0th, as this level contains all nodes
+          assert numNodesOnLevel == size;
+          nodesByLevel[0] = null;
+        } else {
+          nodesByLevel[level] = new int[numNodesOnLevel];
+          for (int i = 0; i < numNodesOnLevel; i++) {
+            nodesByLevel[level][i] = input.readInt();
+          }
+        }
+      }
+
+      // calculate for each level the start offsets in vectorIndex file from where to read
+      // neighbours
+      graphOffsetsByLevel = new long[numLevels];
+      for (int level = 0; level < numLevels; level++) {
+        if (level == 0) {
+          graphOffsetsByLevel[level] = 0;
+        } else {
+          int numNodesOnPrevLevel = level == 1 ? size : nodesByLevel[level - 1].length;
+          graphOffsetsByLevel[level] =
+              graphOffsetsByLevel[level - 1] + (1 + maxConn) * Integer.BYTES * numNodesOnPrevLevel;
+        }
+      }
+    }
+
+    int size() {
+      return size;
+    }
+  }
+
+  /** Read the nearest-neighbors graph from the index input */
+  private static final class OffHeapHnswGraph extends HnswGraph {
+
+    final IndexInput dataIn;
+    final int[][] nodesByLevel;
+    final long[] graphOffsetsByLevel;
+    final int numLevels;
+    final int entryNode;
+    final int size;
+    final long bytesForConns;
+
+    int arcCount;
+    int arcUpTo;
+    int arc;
+
+    OffHeapHnswGraph(FieldEntry entry, IndexInput dataIn) {
+      this.dataIn = dataIn;
+      this.nodesByLevel = entry.nodesByLevel;
+      this.numLevels = entry.numLevels;
+      this.entryNode = numLevels > 1 ? nodesByLevel[numLevels - 1][0] : 0;
+      this.size = entry.size();
+      this.graphOffsetsByLevel = entry.graphOffsetsByLevel;
+      this.bytesForConns = ((long) entry.maxConn + 1) * Integer.BYTES;
+    }
+
+    @Override
+    public void seek(int level, int targetOrd) throws IOException {
+      int targetIndex =
+          level == 0
+              ? targetOrd
+              : Arrays.binarySearch(nodesByLevel[level], 0, nodesByLevel[level].length, targetOrd);
+      assert targetIndex >= 0;
+      long graphDataOffset = graphOffsetsByLevel[level] + targetIndex * bytesForConns;
+      // unsafe; no bounds checking
+      dataIn.seek(graphDataOffset);
+      arcCount = dataIn.readInt();
+      arc = -1;
+      arcUpTo = 0;
+    }
+
+    @Override
+    public int size() {
+      return size;
+    }
+
+    @Override
+    public int nextNeighbor() throws IOException {
+      if (arcUpTo >= arcCount) {
+        return NO_MORE_DOCS;
+      }
+      ++arcUpTo;
+      arc = dataIn.readInt();
+      return arc;
+    }
+
+    @Override
+    public int numLevels() throws IOException {
+      return numLevels;
+    }
+
+    @Override
+    public int entryNode() throws IOException {
+      return entryNode;
+    }
+
+    @Override
+    public NodesIterator getNodesOnLevel(int level) {
+      if (level == 0) {
+        return new NodesIterator(size());
+      } else {
+        return new NodesIterator(nodesByLevel[level], nodesByLevel[level].length);
+      }
+    }
+  }
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene92/Lucene92HnswVectorsWriter.java

@@ -0,0 +1,330 @@
+/*
+ * 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.lucene92;
+
+import static org.apache.lucene.codecs.lucene92.Lucene92HnswVectorsFormat.DIRECT_MONOTONIC_BLOCK_SHIFT;
+import static org.apache.lucene.search.DocIdSetIterator.NO_MORE_DOCS;
+
+import java.io.IOException;
+import java.util.Arrays;
+import org.apache.lucene.codecs.CodecUtil;
+import org.apache.lucene.codecs.KnnVectorsReader;
+import org.apache.lucene.codecs.KnnVectorsWriter;
+import org.apache.lucene.codecs.lucene90.IndexedDISI;
+import org.apache.lucene.index.DocsWithFieldSet;
+import org.apache.lucene.index.FieldInfo;
+import org.apache.lucene.index.IndexFileNames;
+import org.apache.lucene.index.RandomAccessVectorValuesProducer;
+import org.apache.lucene.index.SegmentWriteState;
+import org.apache.lucene.index.VectorSimilarityFunction;
+import org.apache.lucene.index.VectorValues;
+import org.apache.lucene.search.DocIdSetIterator;
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.store.IndexOutput;
+import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.IOUtils;
+import org.apache.lucene.util.hnsw.HnswGraph.NodesIterator;
+import org.apache.lucene.util.hnsw.HnswGraphBuilder;
+import org.apache.lucene.util.hnsw.NeighborArray;
+import org.apache.lucene.util.hnsw.OnHeapHnswGraph;
+import org.apache.lucene.util.packed.DirectMonotonicWriter;
+
+/**
+ * Writes vector values and knn graphs to index segments.
+ *
+ * @lucene.experimental
+ */
+public final class Lucene92HnswVectorsWriter extends KnnVectorsWriter {
+
+  private final SegmentWriteState segmentWriteState;
+  private final IndexOutput meta, vectorData, vectorIndex;
+  private final int maxDoc;
+
+  private final int maxConn;
+  private final int beamWidth;
+  private boolean finished;
+
+  Lucene92HnswVectorsWriter(SegmentWriteState state, int maxConn, int beamWidth)
+      throws IOException {
+    this.maxConn = maxConn;
+    this.beamWidth = beamWidth;
+
+    assert state.fieldInfos.hasVectorValues();
+    segmentWriteState = state;
+
+    String metaFileName =
+        IndexFileNames.segmentFileName(
+            state.segmentInfo.name, state.segmentSuffix, Lucene92HnswVectorsFormat.META_EXTENSION);
+
+    String vectorDataFileName =
+        IndexFileNames.segmentFileName(
+            state.segmentInfo.name,
+            state.segmentSuffix,
+            Lucene92HnswVectorsFormat.VECTOR_DATA_EXTENSION);
+
+    String indexDataFileName =
+        IndexFileNames.segmentFileName(
+            state.segmentInfo.name,
+            state.segmentSuffix,
+            Lucene92HnswVectorsFormat.VECTOR_INDEX_EXTENSION);
+
+    boolean success = false;
+    try {
+      meta = state.directory.createOutput(metaFileName, state.context);
+      vectorData = state.directory.createOutput(vectorDataFileName, state.context);
+      vectorIndex = state.directory.createOutput(indexDataFileName, state.context);
+
+      CodecUtil.writeIndexHeader(
+          meta,
+          Lucene92HnswVectorsFormat.META_CODEC_NAME,
+          Lucene92HnswVectorsFormat.VERSION_CURRENT,
+          state.segmentInfo.getId(),
+          state.segmentSuffix);
+      CodecUtil.writeIndexHeader(
+          vectorData,
+          Lucene92HnswVectorsFormat.VECTOR_DATA_CODEC_NAME,
+          Lucene92HnswVectorsFormat.VERSION_CURRENT,
+          state.segmentInfo.getId(),
+          state.segmentSuffix);
+      CodecUtil.writeIndexHeader(
+          vectorIndex,
+          Lucene92HnswVectorsFormat.VECTOR_INDEX_CODEC_NAME,
+          Lucene92HnswVectorsFormat.VERSION_CURRENT,
+          state.segmentInfo.getId(),
+          state.segmentSuffix);
+      maxDoc = state.segmentInfo.maxDoc();
+      success = true;
+    } finally {
+      if (success == false) {
+        IOUtils.closeWhileHandlingException(this);
+      }
+    }
+  }
+
+  @Override
+  public void writeField(FieldInfo fieldInfo, KnnVectorsReader knnVectorsReader)
+      throws IOException {
+    long vectorDataOffset = vectorData.alignFilePointer(Float.BYTES);
+    VectorValues vectors = knnVectorsReader.getVectorValues(fieldInfo.name);
+
+    IndexOutput tempVectorData =
+        segmentWriteState.directory.createTempOutput(
+            vectorData.getName(), "temp", segmentWriteState.context);
+    IndexInput vectorDataInput = null;
+    boolean success = false;
+    try {
+      // write the vector data to a temporary file
+      DocsWithFieldSet docsWithField = writeVectorData(tempVectorData, vectors);
+      CodecUtil.writeFooter(tempVectorData);
+      IOUtils.close(tempVectorData);
+
+      // copy the temporary file vectors to the actual data file
+      vectorDataInput =
+          segmentWriteState.directory.openInput(
+              tempVectorData.getName(), segmentWriteState.context);
+      vectorData.copyBytes(vectorDataInput, vectorDataInput.length() - CodecUtil.footerLength());
+      CodecUtil.retrieveChecksum(vectorDataInput);
+      long vectorDataLength = vectorData.getFilePointer() - vectorDataOffset;
+
+      long vectorIndexOffset = vectorIndex.getFilePointer();
+      // build the graph using the temporary vector data
+      // we use Lucene92HnswVectorsReader.DenseOffHeapVectorValues for the graph construction
+      // doesn't need to know docIds
+      // TODO: separate random access vector values from DocIdSetIterator?
+      OffHeapVectorValues offHeapVectors =
+          new OffHeapVectorValues.DenseOffHeapVectorValues(
+              vectors.dimension(), docsWithField.cardinality(), vectorDataInput);
+      OnHeapHnswGraph graph =
+          offHeapVectors.size() == 0
+              ? null
+              : writeGraph(offHeapVectors, fieldInfo.getVectorSimilarityFunction());
+      long vectorIndexLength = vectorIndex.getFilePointer() - vectorIndexOffset;
+      writeMeta(
+          fieldInfo,
+          vectorDataOffset,
+          vectorDataLength,
+          vectorIndexOffset,
+          vectorIndexLength,
+          docsWithField,
+          graph);
+      success = true;
+    } finally {
+      IOUtils.close(vectorDataInput);
+      if (success) {
+        segmentWriteState.directory.deleteFile(tempVectorData.getName());
+      } else {
+        IOUtils.closeWhileHandlingException(tempVectorData);
+        IOUtils.deleteFilesIgnoringExceptions(
+            segmentWriteState.directory, tempVectorData.getName());
+      }
+    }
+  }
+
+  /**
+   * Writes the vector values to the output and returns a set of documents that contains vectors.
+   */
+  private static DocsWithFieldSet writeVectorData(IndexOutput output, VectorValues vectors)
+      throws IOException {
+    DocsWithFieldSet docsWithField = new DocsWithFieldSet();
+    for (int docV = vectors.nextDoc(); docV != NO_MORE_DOCS; docV = vectors.nextDoc()) {
+      // write vector
+      BytesRef binaryValue = vectors.binaryValue();
+      assert binaryValue.length == vectors.dimension() * Float.BYTES;
+      output.writeBytes(binaryValue.bytes, binaryValue.offset, binaryValue.length);
+      docsWithField.add(docV);
+    }
+    return docsWithField;
+  }
+
+  private void writeMeta(
+      FieldInfo field,
+      long vectorDataOffset,
+      long vectorDataLength,
+      long vectorIndexOffset,
+      long vectorIndexLength,
+      DocsWithFieldSet docsWithField,
+      OnHeapHnswGraph graph)
+      throws IOException {
+    meta.writeInt(field.number);
+    meta.writeInt(field.getVectorSimilarityFunction().ordinal());
+    meta.writeVLong(vectorDataOffset);
+    meta.writeVLong(vectorDataLength);
+    meta.writeVLong(vectorIndexOffset);
+    meta.writeVLong(vectorIndexLength);
+    meta.writeInt(field.getVectorDimension());
+
+    // write docIDs
+    int count = docsWithField.cardinality();
+    meta.writeInt(count);
+    if (count == 0) {
+      meta.writeLong(-2); // docsWithFieldOffset
+      meta.writeLong(0L); // docsWithFieldLength
+      meta.writeShort((short) -1); // jumpTableEntryCount
+      meta.writeByte((byte) -1); // denseRankPower
+    } else if (count == maxDoc) {
+      meta.writeLong(-1); // docsWithFieldOffset
+      meta.writeLong(0L); // docsWithFieldLength
+      meta.writeShort((short) -1); // jumpTableEntryCount
+      meta.writeByte((byte) -1); // denseRankPower
+    } else {
+      long offset = vectorData.getFilePointer();
+      meta.writeLong(offset); // docsWithFieldOffset
+      final short jumpTableEntryCount =
+          IndexedDISI.writeBitSet(
+              docsWithField.iterator(), vectorData, IndexedDISI.DEFAULT_DENSE_RANK_POWER);
+      meta.writeLong(vectorData.getFilePointer() - offset); // docsWithFieldLength
+      meta.writeShort(jumpTableEntryCount);
+      meta.writeByte(IndexedDISI.DEFAULT_DENSE_RANK_POWER);
+
+      // write ordToDoc mapping
+      long start = vectorData.getFilePointer();
+      meta.writeLong(start);
+      meta.writeVInt(DIRECT_MONOTONIC_BLOCK_SHIFT);
+      // dense case and empty case do not need to store ordToMap mapping
+      final DirectMonotonicWriter ordToDocWriter =
+          DirectMonotonicWriter.getInstance(meta, vectorData, count, DIRECT_MONOTONIC_BLOCK_SHIFT);
+      DocIdSetIterator iterator = docsWithField.iterator();
+      for (int doc = iterator.nextDoc();
+          doc != DocIdSetIterator.NO_MORE_DOCS;
+          doc = iterator.nextDoc()) {
+        ordToDocWriter.add(doc);
+      }
+      ordToDocWriter.finish();
+      meta.writeLong(vectorData.getFilePointer() - start);
+    }
+
+    meta.writeInt(maxConn);
+    // write graph nodes on each level
+    if (graph == null) {
+      meta.writeInt(0);
+    } else {
+      meta.writeInt(graph.numLevels());
+      for (int level = 0; level < graph.numLevels(); level++) {
+        NodesIterator nodesOnLevel = graph.getNodesOnLevel(level);
+        meta.writeInt(nodesOnLevel.size()); // number of nodes on a level
+        if (level > 0) {
+          while (nodesOnLevel.hasNext()) {
+            int node = nodesOnLevel.nextInt();
+            meta.writeInt(node); // list of nodes on a level
+          }
+        }
+      }
+    }
+  }
+
+  private OnHeapHnswGraph writeGraph(
+      RandomAccessVectorValuesProducer vectorValues, VectorSimilarityFunction similarityFunction)
+      throws IOException {
+
+    // build graph
+    HnswGraphBuilder hnswGraphBuilder =
+        new HnswGraphBuilder(
+            vectorValues, similarityFunction, maxConn, beamWidth, HnswGraphBuilder.randSeed);
+    hnswGraphBuilder.setInfoStream(segmentWriteState.infoStream);
+    OnHeapHnswGraph graph = hnswGraphBuilder.build(vectorValues.randomAccess());
+
+    // write vectors' neighbours on each level into the vectorIndex file
+    int countOnLevel0 = graph.size();
+    for (int level = 0; level < graph.numLevels(); level++) {
+      NodesIterator nodesOnLevel = graph.getNodesOnLevel(level);
+      while (nodesOnLevel.hasNext()) {
+        int node = nodesOnLevel.nextInt();
+        NeighborArray neighbors = graph.getNeighbors(level, node);
+        int size = neighbors.size();
+        vectorIndex.writeInt(size);
+        // Destructively modify; it's ok we are discarding it after this
+        int[] nnodes = neighbors.node();
+        Arrays.sort(nnodes, 0, size);
+        for (int i = 0; i < size; i++) {
+          int nnode = nnodes[i];
+          assert nnode < countOnLevel0 : "node too large: " + nnode + ">=" + countOnLevel0;
+          vectorIndex.writeInt(nnode);
+        }
+        // if number of connections < maxConn, add bogus values up to maxConn to have predictable
+        // offsets
+        for (int i = size; i < maxConn; i++) {
+          vectorIndex.writeInt(0);
+        }
+      }
+    }
+    return graph;
+  }
+
+  @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);
+      CodecUtil.writeFooter(vectorIndex);
+    }
+  }
+
+  @Override
+  public void close() throws IOException {
+    IOUtils.close(meta, vectorData, vectorIndex);
+  }
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene92/OffHeapVectorValues.java

@@ -0,0 +1,321 @@
+/*
+ * 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.lucene92;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import org.apache.lucene.codecs.lucene90.IndexedDISI;
+import org.apache.lucene.index.RandomAccessVectorValues;
+import org.apache.lucene.index.RandomAccessVectorValuesProducer;
+import org.apache.lucene.index.VectorValues;
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.store.RandomAccessInput;
+import org.apache.lucene.util.Bits;
+import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.packed.DirectMonotonicReader;
+
+/** Read the vector values from the index input. This supports both iterated and random access. */
+abstract class OffHeapVectorValues extends VectorValues
+    implements RandomAccessVectorValues, RandomAccessVectorValuesProducer {
+
+  protected final int dimension;
+  protected final int size;
+  protected final IndexInput slice;
+  protected final BytesRef binaryValue;
+  protected final ByteBuffer byteBuffer;
+  protected final int byteSize;
+  protected final float[] value;
+
+  OffHeapVectorValues(int dimension, int size, IndexInput slice) {
+    this.dimension = dimension;
+    this.size = size;
+    this.slice = slice;
+    byteSize = Float.BYTES * dimension;
+    byteBuffer = ByteBuffer.allocate(byteSize);
+    value = new float[dimension];
+    binaryValue = new BytesRef(byteBuffer.array(), byteBuffer.arrayOffset(), byteSize);
+  }
+
+  @Override
+  public int dimension() {
+    return dimension;
+  }
+
+  @Override
+  public int size() {
+    return size;
+  }
+
+  @Override
+  public long cost() {
+    return size;
+  }
+
+  @Override
+  public float[] vectorValue(int targetOrd) throws IOException {
+    slice.seek((long) targetOrd * byteSize);
+    slice.readFloats(value, 0, value.length);
+    return value;
+  }
+
+  @Override
+  public BytesRef binaryValue(int targetOrd) throws IOException {
+    readValue(targetOrd);
+    return binaryValue;
+  }
+
+  private void readValue(int targetOrd) throws IOException {
+    slice.seek((long) targetOrd * byteSize);
+    slice.readBytes(byteBuffer.array(), byteBuffer.arrayOffset(), byteSize);
+  }
+
+  public abstract int ordToDoc(int ord);
+
+  static OffHeapVectorValues load(
+      Lucene92HnswVectorsReader.FieldEntry fieldEntry, IndexInput vectorData) throws IOException {
+    if (fieldEntry.docsWithFieldOffset == -2) {
+      return new EmptyOffHeapVectorValues(fieldEntry.dimension);
+    }
+    IndexInput bytesSlice =
+        vectorData.slice("vector-data", fieldEntry.vectorDataOffset, fieldEntry.vectorDataLength);
+    if (fieldEntry.docsWithFieldOffset == -1) {
+      return new DenseOffHeapVectorValues(fieldEntry.dimension, fieldEntry.size, bytesSlice);
+    } else {
+      return new SparseOffHeapVectorValues(fieldEntry, vectorData, bytesSlice);
+    }
+  }
+
+  abstract Bits getAcceptOrds(Bits acceptDocs);
+
+  static class DenseOffHeapVectorValues extends OffHeapVectorValues {
+
+    private int doc = -1;
+
+    public DenseOffHeapVectorValues(int dimension, int size, IndexInput slice) {
+      super(dimension, size, slice);
+    }
+
+    @Override
+    public float[] vectorValue() throws IOException {
+      slice.seek((long) doc * byteSize);
+      slice.readFloats(value, 0, value.length);
+      return value;
+    }
+
+    @Override
+    public BytesRef binaryValue() throws IOException {
+      slice.seek((long) doc * byteSize);
+      slice.readBytes(byteBuffer.array(), byteBuffer.arrayOffset(), byteSize, false);
+      return binaryValue;
+    }
+
+    @Override
+    public int docID() {
+      return doc;
+    }
+
+    @Override
+    public int nextDoc() throws IOException {
+      return advance(doc + 1);
+    }
+
+    @Override
+    public int advance(int target) throws IOException {
+      assert docID() < target;
+      if (target >= size) {
+        return doc = NO_MORE_DOCS;
+      }
+      return doc = target;
+    }
+
+    @Override
+    public RandomAccessVectorValues randomAccess() throws IOException {
+      return new DenseOffHeapVectorValues(dimension, size, slice.clone());
+    }
+
+    @Override
+    public int ordToDoc(int ord) {
+      return ord;
+    }
+
+    @Override
+    Bits getAcceptOrds(Bits acceptDocs) {
+      return acceptDocs;
+    }
+  }
+
+  private static class SparseOffHeapVectorValues extends OffHeapVectorValues {
+    private final DirectMonotonicReader ordToDoc;
+    private final IndexedDISI disi;
+    // dataIn was used to init a new IndexedDIS for #randomAccess()
+    private final IndexInput dataIn;
+    private final Lucene92HnswVectorsReader.FieldEntry fieldEntry;
+
+    public SparseOffHeapVectorValues(
+        Lucene92HnswVectorsReader.FieldEntry fieldEntry, IndexInput dataIn, IndexInput slice)
+        throws IOException {
+
+      super(fieldEntry.dimension, fieldEntry.size, slice);
+      this.fieldEntry = fieldEntry;
+      final RandomAccessInput addressesData =
+          dataIn.randomAccessSlice(fieldEntry.addressesOffset, fieldEntry.addressesLength);
+      this.dataIn = dataIn;
+      this.ordToDoc = DirectMonotonicReader.getInstance(fieldEntry.meta, addressesData);
+      this.disi =
+          new IndexedDISI(
+              dataIn,
+              fieldEntry.docsWithFieldOffset,
+              fieldEntry.docsWithFieldLength,
+              fieldEntry.jumpTableEntryCount,
+              fieldEntry.denseRankPower,
+              fieldEntry.size);
+    }
+
+    @Override
+    public float[] vectorValue() throws IOException {
+      slice.seek((long) (disi.index()) * byteSize);
+      slice.readFloats(value, 0, value.length);
+      return value;
+    }
+
+    @Override
+    public BytesRef binaryValue() throws IOException {
+      slice.seek((long) (disi.index()) * byteSize);
+      slice.readBytes(byteBuffer.array(), byteBuffer.arrayOffset(), byteSize, false);
+      return binaryValue;
+    }
+
+    @Override
+    public int docID() {
+      return disi.docID();
+    }
+
+    @Override
+    public int nextDoc() throws IOException {
+      return disi.nextDoc();
+    }
+
+    @Override
+    public int advance(int target) throws IOException {
+      assert docID() < target;
+      return disi.advance(target);
+    }
+
+    @Override
+    public RandomAccessVectorValues randomAccess() throws IOException {
+      return new SparseOffHeapVectorValues(fieldEntry, dataIn, slice.clone());
+    }
+
+    @Override
+    public int ordToDoc(int ord) {
+      return (int) ordToDoc.get(ord);
+    }
+
+    @Override
+    Bits getAcceptOrds(Bits acceptDocs) {
+      if (acceptDocs == null) {
+        return null;
+      }
+      return new Bits() {
+        @Override
+        public boolean get(int index) {
+          return acceptDocs.get(ordToDoc(index));
+        }
+
+        @Override
+        public int length() {
+          return size;
+        }
+      };
+    }
+  }
+
+  private static class EmptyOffHeapVectorValues extends OffHeapVectorValues {
+
+    public EmptyOffHeapVectorValues(int dimension) {
+      super(dimension, 0, null);
+    }
+
+    private int doc = -1;
+
+    @Override
+    public int dimension() {
+      return super.dimension();
+    }
+
+    @Override
+    public int size() {
+      return 0;
+    }
+
+    @Override
+    public float[] vectorValue() throws IOException {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public BytesRef binaryValue() throws IOException {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public int docID() {
+      return doc;
+    }
+
+    @Override
+    public int nextDoc() throws IOException {
+      return advance(doc + 1);
+    }
+
+    @Override
+    public int advance(int target) throws IOException {
+      return doc = NO_MORE_DOCS;
+    }
+
+    @Override
+    public long cost() {
+      return 0;
+    }
+
+    @Override
+    public RandomAccessVectorValues randomAccess() throws IOException {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public float[] vectorValue(int targetOrd) throws IOException {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public BytesRef binaryValue(int targetOrd) throws IOException {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public int ordToDoc(int ord) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    Bits getAcceptOrds(Bits acceptDocs) {
+      return null;
+    }
+  }
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene92/package-info.java

@@ -0,0 +1,422 @@
+/*
+ * 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 9.2 file format.
+ *
+ * <h2>Apache Lucene - Index File Formats</h2>
+ *
+ * <div>
+ *
+ * <ul>
+ *   <li><a href="#Introduction">Introduction</a>
+ *   <li><a href="#Definitions">Definitions</a>
+ *       <ul>
+ *         <li><a href="#Inverted_Indexing">Inverted Indexing</a>
+ *         <li><a href="#Types_of_Fields">Types of Fields</a>
+ *         <li><a href="#Segments">Segments</a>
+ *         <li><a href="#Document_Numbers">Document Numbers</a>
+ *       </ul>
+ *   <li><a href="#Overview">Index Structure Overview</a>
+ *   <li><a href="#File_Naming">File Naming</a>
+ *   <li><a href="#file-names">Summary of File Extensions</a>
+ *       <ul>
+ *         <li><a href="#Lock_File">Lock File</a>
+ *         <li><a href="#History">History</a>
+ *         <li><a href="#Limitations">Limitations</a>
+ *       </ul>
+ * </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>This document attempts to provide a high-level definition of the Apache Lucene file formats.
+ * </div> <a id="Definitions"></a>
+ *
+ * <h3>Definitions</h3>
+ *
+ * <div>
+ *
+ * <p>The fundamental concepts in Lucene are index, document, field and term.
+ *
+ * <p>An index contains a sequence of documents.
+ *
+ * <ul>
+ *   <li>A document is a sequence of fields.
+ *   <li>A field is a named sequence of terms.
+ *   <li>A term is a sequence of bytes.
+ * </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. <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. <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>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>See the {@link org.apache.lucene.document.Field Field} java docs for more information on
+ * Fields. <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:
+ *
+ * <ol>
+ *   <li>Creating new segments for newly added documents.
+ *   <li>Merging existing segments.
+ * </ol>
+ *
+ * <p>Searches may involve multiple segments and/or multiple indexes, each index potentially
+ * composed of a set of segments. <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>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:
+ *
+ * <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.
+ *   <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.
+ * </ul>
+ *
+ * </div> <a id="Overview"></a>
+ *
+ * <h3>Index Structure Overview</h3>
+ *
+ * <div>
+ *
+ * <p>Each segment index maintains the following:
+ *
+ * <ul>
+ *   <li>{@link org.apache.lucene.codecs.lucene90.Lucene90SegmentInfoFormat 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>{@link org.apache.lucene.codecs.lucene90.Lucene90FieldInfosFormat Field names}. This
+ *       contains metadata about the set of named fields used in the index.
+ *   <li>{@link org.apache.lucene.codecs.lucene90.Lucene90StoredFieldsFormat 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>{@link org.apache.lucene.codecs.lucene90.Lucene90PostingsFormat 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>{@link org.apache.lucene.codecs.lucene90.Lucene90PostingsFormat 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>{@link org.apache.lucene.codecs.lucene90.Lucene90PostingsFormat 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>{@link org.apache.lucene.codecs.lucene90.Lucene90NormsFormat Normalization factors}. For
+ *       each field in each document, a value is stored that is multiplied into the score for hits
+ *       on that field.
+ *   <li>{@link org.apache.lucene.codecs.lucene90.Lucene90TermVectorsFormat 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>{@link org.apache.lucene.codecs.lucene90.Lucene90DocValuesFormat 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>{@link org.apache.lucene.codecs.lucene90.Lucene90LiveDocsFormat Live documents}. An
+ *       optional file indicating which documents are live.
+ *   <li>{@link org.apache.lucene.codecs.lucene90.Lucene90PointsFormat 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>{@link org.apache.lucene.codecs.lucene92.Lucene92HnswVectorsFormat Vector values}. The
+ *       vector format stores numeric vectors in a format optimized for random access and
+ *       computation, supporting high-dimensional nearest-neighbor search.
+ * </ul>
+ *
+ * <p>Details on each of these are provided in their linked pages. </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>Typically, all segments in an index are stored in a single directory, although this is not
+ * required.
+ *
+ * <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. </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:
+ *
+ * <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.lucene90.Lucene90SegmentInfoFormat Segment Info}</td>
+ * <td>.si</td>
+ * <td>Stores metadata about a segment</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene90.Lucene90CompoundFormat 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.lucene90.Lucene90FieldInfosFormat Fields}</td>
+ * <td>.fnm</td>
+ * <td>Stores information about the fields</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene90.Lucene90StoredFieldsFormat Field Index}</td>
+ * <td>.fdx</td>
+ * <td>Contains pointers to field data</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene90.Lucene90StoredFieldsFormat Field Data}</td>
+ * <td>.fdt</td>
+ * <td>The stored fields for documents</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene90.Lucene90PostingsFormat Term Dictionary}</td>
+ * <td>.tim</td>
+ * <td>The term dictionary, stores term info</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene90.Lucene90PostingsFormat Term Index}</td>
+ * <td>.tip</td>
+ * <td>The index into the Term Dictionary</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene90.Lucene90PostingsFormat 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.lucene90.Lucene90PostingsFormat 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.lucene90.Lucene90PostingsFormat 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.lucene90.Lucene90NormsFormat 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.lucene90.Lucene90DocValuesFormat 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.lucene90.Lucene90TermVectorsFormat Term Vector Index}</td>
+ * <td>.tvx</td>
+ * <td>Stores offset into the document data file</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene90.Lucene90TermVectorsFormat Term Vector Data}</td>
+ * <td>.tvd</td>
+ * <td>Contains term vector data.</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene90.Lucene90LiveDocsFormat Live Documents}</td>
+ * <td>.liv</td>
+ * <td>Info about what documents are live</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene90.Lucene90PointsFormat Point values}</td>
+ * <td>.dii, .dim</td>
+ * <td>Holds indexed points</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene92.Lucene92HnswVectorsFormat 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:
+ *
+ * <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>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>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>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>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>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>In version 3.2, numeric fields are written as natively to stored fields file, previously
+ *       they were stored in text format only.
+ *   <li>In version 3.4, fields can omit position data while still indexing term frequencies.
+ *   <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>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>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>In version 4.5, DocValues were extended to explicitly represent missing values.
+ *   <li>In version 4.6, FieldInfos were extended to support per-field DocValues generation, to
+ *       allow updating NumericDocValues fields.
+ *   <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>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>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>In version 8.4, postings, positions, offsets and payload lengths have move to a more
+ *       performant encoding that is vectorized.
+ *   <li>In version 8.6, index sort serialization is delegated to the sorts themselves, to allow
+ *       user-defined sorts to be used
+ *   <li>In version 8.7, stored fields compression became adaptive to better handle documents with
+ *       smaller stored fields.
+ *   <li>In version 9.0, vector-valued fields were added.
+ *   <li>In version 9.1, vector-valued fields were modified to add a graph hierarchy.
+ *   <li>In version 9.2, docs of vector-valued fields were moved from .vem to .vec and encoded by
+ *       IndexDISI. ordToDoc mappings was added to .vem.
+ * </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. </div>
+ */
+package org.apache.lucene.codecs.lucene92;

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

@@ -17,6 +17,8 @@
 
 package org.apache.lucene.index;
 
+import java.io.IOException;
+
 /**
  * Something (generally a {@link VectorValues}) that provides a {@link RandomAccessVectorValues}.
  *
@@ -29,5 +31,5 @@ public interface RandomAccessVectorValuesProducer {
    * Successive calls will retrieve independent copies that do not overwrite each others' returned
    * values.
    */
-  RandomAccessVectorValues randomAccess();
+  RandomAccessVectorValues randomAccess() throws IOException;
 }

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

@@ -225,7 +225,7 @@ class VectorValuesWriter {
     }
 
     @Override
-    public RandomAccessVectorValues randomAccess() {
+    public RandomAccessVectorValues randomAccess() throws IOException {
 
       // Must make a new delegate randomAccess so that we have our own distinct float[]
       final RandomAccessVectorValues delegateRA =

lucene/core/src/java/org/apache/lucene/util/hnsw/HnswGraphBuilder.java

@@ -79,7 +79,8 @@ public final class HnswGraphBuilder {
       VectorSimilarityFunction similarityFunction,
       int maxConn,
       int beamWidth,
-      long seed) {
+      long seed)
+      throws IOException {
     vectorValues = vectors.randomAccess();
     buildVectors = vectors.randomAccess();
     this.similarityFunction = Objects.requireNonNull(similarityFunction);

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.lucene91.Lucene91Codec
+org.apache.lucene.codecs.lucene92.Lucene92Codec

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

@@ -13,4 +13,4 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsFormat
+org.apache.lucene.codecs.lucene92.Lucene92HnswVectorsFormat

lucene/core/src/test/org/apache/lucene/codecs/lucene90/TestLucene90StoredFieldsFormatHighCompression.java

@@ -18,8 +18,8 @@ package org.apache.lucene.codecs.lucene90;
 
 import com.carrotsearch.randomizedtesting.generators.RandomPicks;
 import org.apache.lucene.codecs.Codec;
-import org.apache.lucene.codecs.lucene91.Lucene91Codec;
-import org.apache.lucene.codecs.lucene91.Lucene91Codec.Mode;
+import org.apache.lucene.codecs.lucene92.Lucene92Codec;
+import org.apache.lucene.codecs.lucene92.Lucene92Codec.Mode;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.StoredField;
 import org.apache.lucene.index.DirectoryReader;
@@ -31,7 +31,7 @@ import org.apache.lucene.tests.index.BaseStoredFieldsFormatTestCase;
 public class TestLucene90StoredFieldsFormatHighCompression extends BaseStoredFieldsFormatTestCase {
   @Override
   protected Codec getCodec() {
-    return new Lucene91Codec(Mode.BEST_COMPRESSION);
+    return new Lucene92Codec(Mode.BEST_COMPRESSION);
   }
 
   /**
@@ -41,7 +41,7 @@ public class TestLucene90StoredFieldsFormatHighCompression extends BaseStoredFie
     Directory dir = newDirectory();
     for (int i = 0; i < 10; i++) {
       IndexWriterConfig iwc = newIndexWriterConfig();
-      iwc.setCodec(new Lucene91Codec(RandomPicks.randomFrom(random(), Mode.values())));
+      iwc.setCodec(new Lucene92Codec(RandomPicks.randomFrom(random(), Mode.values())));
       IndexWriter iw = new IndexWriter(dir, newIndexWriterConfig());
       Document doc = new Document();
       doc.add(new StoredField("field1", "value1"));
@@ -70,7 +70,7 @@ public class TestLucene90StoredFieldsFormatHighCompression extends BaseStoredFie
     expectThrows(
         NullPointerException.class,
         () -> {
-          new Lucene91Codec(null);
+          new Lucene92Codec(null);
         });
 
     expectThrows(

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

@@ -30,9 +30,9 @@ import java.util.Set;
 import java.util.concurrent.CountDownLatch;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.KnnVectorsFormat;
-import org.apache.lucene.codecs.lucene91.Lucene91Codec;
-import org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsFormat;
-import org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsReader;
+import org.apache.lucene.codecs.lucene92.Lucene92Codec;
+import org.apache.lucene.codecs.lucene92.Lucene92HnswVectorsFormat;
+import org.apache.lucene.codecs.lucene92.Lucene92HnswVectorsReader;
 import org.apache.lucene.codecs.perfield.PerFieldKnnVectorsFormat;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
@@ -64,7 +64,7 @@ public class TestKnnGraph extends LuceneTestCase {
 
   private static final String KNN_GRAPH_FIELD = "vector";
 
-  private static int maxConn = Lucene91HnswVectorsFormat.DEFAULT_MAX_CONN;
+  private static int maxConn = Lucene92HnswVectorsFormat.DEFAULT_MAX_CONN;
 
   private Codec codec;
   private VectorSimilarityFunction similarityFunction;
@@ -77,11 +77,11 @@ public class TestKnnGraph extends LuceneTestCase {
     }
 
     codec =
-        new Lucene91Codec() {
+        new Lucene92Codec() {
           @Override
           public KnnVectorsFormat getKnnVectorsFormatForField(String field) {
-            return new Lucene91HnswVectorsFormat(
-                maxConn, Lucene91HnswVectorsFormat.DEFAULT_BEAM_WIDTH);
+            return new Lucene92HnswVectorsFormat(
+                maxConn, Lucene92HnswVectorsFormat.DEFAULT_BEAM_WIDTH);
           }
         };
 
@@ -91,7 +91,7 @@ public class TestKnnGraph extends LuceneTestCase {
 
   @After
   public void cleanup() {
-    maxConn = Lucene91HnswVectorsFormat.DEFAULT_MAX_CONN;
+    maxConn = Lucene92HnswVectorsFormat.DEFAULT_MAX_CONN;
   }
 
   /** Basic test of creating documents in a graph */
@@ -238,8 +238,8 @@ public class TestKnnGraph extends LuceneTestCase {
         PerFieldKnnVectorsFormat.FieldsReader perFieldReader =
             (PerFieldKnnVectorsFormat.FieldsReader)
                 ((CodecReader) getOnlyLeafReader(reader)).getVectorReader();
-        Lucene91HnswVectorsReader vectorReader =
-            (Lucene91HnswVectorsReader) perFieldReader.getFieldReader(KNN_GRAPH_FIELD);
+        Lucene92HnswVectorsReader vectorReader =
+            (Lucene92HnswVectorsReader) perFieldReader.getFieldReader(KNN_GRAPH_FIELD);
         graph = copyGraph(vectorReader.getGraph(KNN_GRAPH_FIELD));
       }
     }
@@ -437,8 +437,8 @@ public class TestKnnGraph extends LuceneTestCase {
         if (perFieldReader == null) {
           continue;
         }
-        Lucene91HnswVectorsReader vectorReader =
-            (Lucene91HnswVectorsReader) perFieldReader.getFieldReader(vectorField);
+        Lucene92HnswVectorsReader vectorReader =
+            (Lucene92HnswVectorsReader) perFieldReader.getFieldReader(vectorField);
         if (vectorReader == null) {
           continue;
         }
@@ -451,8 +451,9 @@ public class TestKnnGraph extends LuceneTestCase {
 
         // assert vector values:
         // stored vector values are the same as original
+        int nextDocWithVectors = 0;
         for (int i = 0; i < reader.maxDoc(); i++) {
-          int nextDocWithVectors = vectorValues.advance(i);
+          nextDocWithVectors = vectorValues.advance(i);
           while (i < nextDocWithVectors && i < reader.maxDoc()) {
             int id = Integer.parseInt(reader.document(i).get("id"));
             assertNull("document " + id + " has no vector, but was expected to", values[id]);
@@ -471,7 +472,12 @@ public class TestKnnGraph extends LuceneTestCase {
               0f);
           numDocsWithVectors++;
         }
-        assertEquals(NO_MORE_DOCS, vectorValues.nextDoc());
+        // if IndexDisi.doc == NO_MORE_DOCS, we should not call IndexDisi.nextDoc()
+        if (nextDocWithVectors != NO_MORE_DOCS) {
+          assertEquals(NO_MORE_DOCS, vectorValues.nextDoc());
+        } else {
+          assertEquals(NO_MORE_DOCS, vectorValues.docID());
+        }
 
         // assert graph values:
         // For each level of the graph assert that:

lucene/core/src/test/org/apache/lucene/util/hnsw/KnnGraphTester.java

@@ -39,9 +39,9 @@ import java.util.Objects;
 import java.util.Set;
 import org.apache.lucene.codecs.KnnVectorsFormat;
 import org.apache.lucene.codecs.KnnVectorsReader;
-import org.apache.lucene.codecs.lucene91.Lucene91Codec;
-import org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsFormat;
-import org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsReader;
+import org.apache.lucene.codecs.lucene92.Lucene92Codec;
+import org.apache.lucene.codecs.lucene92.Lucene92HnswVectorsFormat;
+import org.apache.lucene.codecs.lucene92.Lucene92HnswVectorsReader;
 import org.apache.lucene.codecs.perfield.PerFieldKnnVectorsFormat;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.FieldType;
@@ -248,7 +248,7 @@ public class KnnGraphTester {
         KnnVectorsReader vectorsReader =
             ((PerFieldKnnVectorsFormat.FieldsReader) ((CodecReader) leafReader).getVectorReader())
                 .getFieldReader(KNN_FIELD);
-        HnswGraph knnValues = ((Lucene91HnswVectorsReader) vectorsReader).getGraph(KNN_FIELD);
+        HnswGraph knnValues = ((Lucene92HnswVectorsReader) vectorsReader).getGraph(KNN_FIELD);
         System.out.printf("Leaf %d has %d documents\n", context.ord, leafReader.maxDoc());
         printGraphFanout(knnValues, leafReader.maxDoc());
       }
@@ -580,10 +580,10 @@ public class KnnGraphTester {
   private int createIndex(Path docsPath, Path indexPath) throws IOException {
     IndexWriterConfig iwc = new IndexWriterConfig().setOpenMode(IndexWriterConfig.OpenMode.CREATE);
     iwc.setCodec(
-        new Lucene91Codec() {
+        new Lucene92Codec() {
           @Override
           public KnnVectorsFormat getKnnVectorsFormatForField(String field) {
-            return new Lucene91HnswVectorsFormat(maxConn, beamWidth);
+            return new Lucene92HnswVectorsFormat(maxConn, beamWidth);
           }
         });
     // iwc.setMergePolicy(NoMergePolicy.INSTANCE);

lucene/core/src/test/org/apache/lucene/util/hnsw/TestHnswGraph.java

@@ -25,9 +25,9 @@ import java.util.HashSet;
 import java.util.Random;
 import java.util.Set;
 import org.apache.lucene.codecs.KnnVectorsFormat;
-import org.apache.lucene.codecs.lucene91.Lucene91Codec;
-import org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsFormat;
-import org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsReader;
+import org.apache.lucene.codecs.lucene92.Lucene92Codec;
+import org.apache.lucene.codecs.lucene92.Lucene92HnswVectorsFormat;
+import org.apache.lucene.codecs.lucene92.Lucene92HnswVectorsReader;
 import org.apache.lucene.codecs.perfield.PerFieldKnnVectorsFormat;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.KnnVectorField;
@@ -81,10 +81,10 @@ public class TestHnswGraph extends LuceneTestCase {
       IndexWriterConfig iwc =
           new IndexWriterConfig()
               .setCodec(
-                  new Lucene91Codec() {
+                  new Lucene92Codec() {
                     @Override
                     public KnnVectorsFormat getKnnVectorsFormatForField(String field) {
-                      return new Lucene91HnswVectorsFormat(maxConn, beamWidth);
+                      return new Lucene92HnswVectorsFormat(maxConn, beamWidth);
                     }
                   });
       try (IndexWriter iw = new IndexWriter(dir, iwc)) {
@@ -111,7 +111,7 @@ public class TestHnswGraph extends LuceneTestCase {
           assertEquals(indexedDoc, ctx.reader().numDocs());
           assertVectorsEqual(v3, values);
           HnswGraph graphValues =
-              ((Lucene91HnswVectorsReader)
+              ((Lucene92HnswVectorsReader)
                       ((PerFieldKnnVectorsFormat.FieldsReader)
                               ((CodecReader) ctx.reader()).getVectorReader())
                           .getFieldReader("field"))

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

@@ -40,7 +40,7 @@ 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.lucene91.Lucene91Codec;
+import org.apache.lucene.codecs.lucene92.Lucene92Codec;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.IntPoint;
@@ -959,7 +959,7 @@ public class TestSuggestField extends LuceneTestCase {
     IndexWriterConfig iwc = newIndexWriterConfig(random(), analyzer);
     iwc.setMergePolicy(newLogMergePolicy());
     Codec filterCodec =
-        new Lucene91Codec() {
+        new Lucene92Codec() {
           CompletionPostingsFormat.FSTLoadMode fstLoadMode =
               RandomPicks.randomFrom(random(), CompletionPostingsFormat.FSTLoadMode.values());
           PostingsFormat postingsFormat = new Completion90PostingsFormat(fstLoadMode);

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

@@ -38,7 +38,7 @@ import java.util.TimeZone;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.DocValuesFormat;
 import org.apache.lucene.codecs.PostingsFormat;
-import org.apache.lucene.codecs.lucene91.Lucene91Codec;
+import org.apache.lucene.codecs.lucene92.Lucene92Codec;
 import org.apache.lucene.codecs.simpletext.SimpleTextCodec;
 import org.apache.lucene.search.similarities.Similarity;
 import org.apache.lucene.tests.codecs.asserting.AssertingCodec;
@@ -193,9 +193,9 @@ final class TestRuleSetupAndRestoreClassEnv extends AbstractBeforeAfterRule {
     } else if ("Compressing".equals(TEST_CODEC)
         || ("random".equals(TEST_CODEC) && randomVal == 6 && !shouldAvoidCodec("Compressing"))) {
       codec = CompressingCodec.randomInstance(random);
-    } else if ("Lucene91".equals(TEST_CODEC)
-        || ("random".equals(TEST_CODEC) && randomVal == 5 && !shouldAvoidCodec("Lucene91"))) {
-      codec = new Lucene91Codec(RandomPicks.randomFrom(random, Lucene91Codec.Mode.values()));
+    } else if ("Lucene92".equals(TEST_CODEC)
+        || ("random".equals(TEST_CODEC) && randomVal == 5 && !shouldAvoidCodec("Lucene92"))) {
+      codec = new Lucene92Codec(RandomPicks.randomFrom(random, Lucene92Codec.Mode.values()));
     } else if (!"random".equals(TEST_CODEC)) {
       codec = Codec.forName(TEST_CODEC);
     } else if ("random".equals(TEST_POSTINGSFORMAT)) {

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

@@ -55,8 +55,8 @@ import org.apache.lucene.codecs.PostingsFormat;
 import org.apache.lucene.codecs.blocktreeords.BlockTreeOrdsPostingsFormat;
 import org.apache.lucene.codecs.lucene90.Lucene90DocValuesFormat;
 import org.apache.lucene.codecs.lucene90.Lucene90PostingsFormat;
-import org.apache.lucene.codecs.lucene91.Lucene91Codec;
-import org.apache.lucene.codecs.lucene91.Lucene91HnswVectorsFormat;
+import org.apache.lucene.codecs.lucene92.Lucene92Codec;
+import org.apache.lucene.codecs.lucene92.Lucene92HnswVectorsFormat;
 import org.apache.lucene.codecs.perfield.PerFieldDocValuesFormat;
 import org.apache.lucene.codecs.perfield.PerFieldPostingsFormat;
 import org.apache.lucene.document.BinaryDocValuesField;
@@ -1236,7 +1236,7 @@ public final class TestUtil {
    * different than {@link Codec#getDefault()} because that is randomized.
    */
   public static Codec getDefaultCodec() {
-    return new Lucene91Codec();
+    return new Lucene92Codec();
   }
 
   /**
@@ -1322,7 +1322,7 @@ public final class TestUtil {
    * Lucene.
    */
   public static KnnVectorsFormat getDefaultKnnVectorsFormat() {
-    return new Lucene91HnswVectorsFormat();
+    return new Lucene92HnswVectorsFormat();
   }
 
   public static boolean anyFilesExceptWriteLock(Directory dir) throws IOException {