Revert "Simplify advancing on postings/impacts enums (#12810)"

This reverts commit 5aa401e7d8.

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/Lucene50MultiLevelSkipListReader.java

@@ -1,263 +0,0 @@
-/*
- * 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;
-
-import java.io.Closeable;
-import java.io.IOException;
-import java.util.Arrays;
-import org.apache.lucene.backward_codecs.lucene90.Lucene90PostingsFormat;
-import org.apache.lucene.codecs.Lucene99MultiLevelSkipListReader;
-import org.apache.lucene.codecs.MultiLevelSkipListWriter;
-import org.apache.lucene.store.DataOutput;
-import org.apache.lucene.store.IndexInput;
-import org.apache.lucene.store.IndexOutput;
-import org.apache.lucene.util.MathUtil;
-
-/**
- * Legacy variant of {@link Lucene99MultiLevelSkipListReader} for Lucene postings formats up to
- * {@link Lucene90PostingsFormat} included. It starts postings at 0 rather than -1.
- */
-public abstract class Lucene50MultiLevelSkipListReader implements Closeable {
-  /** the maximum number of skip levels possible for this index */
-  protected int maxNumberOfSkipLevels;
-
-  /** number of levels in this skip list */
-  protected int numberOfSkipLevels;
-
-  private int docCount;
-
-  /** skipStream for each level. */
-  private IndexInput[] skipStream;
-
-  /** The start pointer of each skip level. */
-  private long[] skipPointer;
-
-  /** skipInterval of each level. */
-  private int[] skipInterval;
-
-  /**
-   * Number of docs skipped per level. It's possible for some values to overflow a signed int, but
-   * this has been accounted for.
-   */
-  private int[] numSkipped;
-
-  /** Doc id of current skip entry per level. */
-  protected int[] skipDoc;
-
-  /** Doc id of last read skip entry with docId <= target. */
-  private int lastDoc;
-
-  /** Child pointer of current skip entry per level. */
-  private long[] childPointer;
-
-  /** childPointer of last read skip entry with docId <= target. */
-  private long lastChildPointer;
-
-  private final int skipMultiplier;
-
-  /** Creates a {@code MultiLevelSkipListReader}. */
-  protected Lucene50MultiLevelSkipListReader(
-      IndexInput skipStream, int maxSkipLevels, int skipInterval, int skipMultiplier) {
-    this.skipStream = new IndexInput[maxSkipLevels];
-    this.skipPointer = new long[maxSkipLevels];
-    this.childPointer = new long[maxSkipLevels];
-    this.numSkipped = new int[maxSkipLevels];
-    this.maxNumberOfSkipLevels = maxSkipLevels;
-    this.skipInterval = new int[maxSkipLevels];
-    this.skipMultiplier = skipMultiplier;
-    this.skipStream[0] = skipStream;
-    this.skipInterval[0] = skipInterval;
-    for (int i = 1; i < maxSkipLevels; i++) {
-      // cache skip intervals
-      this.skipInterval[i] = this.skipInterval[i - 1] * skipMultiplier;
-    }
-    skipDoc = new int[maxSkipLevels];
-  }
-
-  /**
-   * Creates a {@code MultiLevelSkipListReader}, where {@code skipInterval} and {@code
-   * skipMultiplier} are the same.
-   */
-  protected Lucene50MultiLevelSkipListReader(
-      IndexInput skipStream, int maxSkipLevels, int skipInterval) {
-    this(skipStream, maxSkipLevels, skipInterval, skipInterval);
-  }
-
-  /** Returns the id of the doc to which the last call of {@link #skipTo(int)} has skipped. */
-  public int getDoc() {
-    return lastDoc;
-  }
-
-  /**
-   * Skips entries to the first beyond the current whose document number is greater than or equal to
-   * <i>target</i>. Returns the current doc count.
-   */
-  public int skipTo(int target) throws IOException {
-
-    // walk up the levels until highest level is found that has a skip
-    // for this target
-    int level = 0;
-    while (level < numberOfSkipLevels - 1 && target > skipDoc[level + 1]) {
-      level++;
-    }
-
-    while (level >= 0) {
-      if (target > skipDoc[level]) {
-        if (!loadNextSkip(level)) {
-          continue;
-        }
-      } else {
-        // no more skips on this level, go down one level
-        if (level > 0 && lastChildPointer > skipStream[level - 1].getFilePointer()) {
-          seekChild(level - 1);
-        }
-        level--;
-      }
-    }
-
-    return numSkipped[0] - skipInterval[0] - 1;
-  }
-
-  private boolean loadNextSkip(int level) throws IOException {
-    // we have to skip, the target document is greater than the current
-    // skip list entry
-    setLastSkipData(level);
-
-    numSkipped[level] += skipInterval[level];
-
-    // numSkipped may overflow a signed int, so compare as unsigned.
-    if (Integer.compareUnsigned(numSkipped[level], docCount) > 0) {
-      // this skip list is exhausted
-      skipDoc[level] = Integer.MAX_VALUE;
-      if (numberOfSkipLevels > level) numberOfSkipLevels = level;
-      return false;
-    }
-
-    // read next skip entry
-    skipDoc[level] += readSkipData(level, skipStream[level]);
-
-    if (level != 0) {
-      // read the child pointer if we are not on the leaf level
-      childPointer[level] = readChildPointer(skipStream[level]) + skipPointer[level - 1];
-    }
-
-    return true;
-  }
-
-  /** Seeks the skip entry on the given level */
-  protected void seekChild(int level) throws IOException {
-    skipStream[level].seek(lastChildPointer);
-    numSkipped[level] = numSkipped[level + 1] - skipInterval[level + 1];
-    skipDoc[level] = lastDoc;
-    if (level > 0) {
-      childPointer[level] = readChildPointer(skipStream[level]) + skipPointer[level - 1];
-    }
-  }
-
-  @Override
-  public void close() throws IOException {
-    for (int i = 1; i < skipStream.length; i++) {
-      if (skipStream[i] != null) {
-        skipStream[i].close();
-      }
-    }
-  }
-
-  /** Initializes the reader, for reuse on a new term. */
-  public void init(long skipPointer, int df) throws IOException {
-    this.skipPointer[0] = skipPointer;
-    this.docCount = df;
-    assert skipPointer >= 0 && skipPointer <= skipStream[0].length()
-        : "invalid skip pointer: " + skipPointer + ", length=" + skipStream[0].length();
-    Arrays.fill(skipDoc, 0);
-    Arrays.fill(numSkipped, 0);
-    Arrays.fill(childPointer, 0);
-
-    for (int i = 1; i < numberOfSkipLevels; i++) {
-      skipStream[i] = null;
-    }
-    loadSkipLevels();
-  }
-
-  /** Loads the skip levels */
-  private void loadSkipLevels() throws IOException {
-    if (docCount <= skipInterval[0]) {
-      numberOfSkipLevels = 1;
-    } else {
-      numberOfSkipLevels = 1 + MathUtil.log(docCount / skipInterval[0], skipMultiplier);
-    }
-
-    if (numberOfSkipLevels > maxNumberOfSkipLevels) {
-      numberOfSkipLevels = maxNumberOfSkipLevels;
-    }
-
-    skipStream[0].seek(skipPointer[0]);
-
-    for (int i = numberOfSkipLevels - 1; i > 0; i--) {
-      // the length of the current level
-      long length = readLevelLength(skipStream[0]);
-
-      // the start pointer of the current level
-      skipPointer[i] = skipStream[0].getFilePointer();
-
-      // clone this stream, it is already at the start of the current level
-      skipStream[i] = skipStream[0].clone();
-
-      // move base stream beyond the current level
-      skipStream[0].seek(skipStream[0].getFilePointer() + length);
-    }
-
-    // use base stream for the lowest level
-    skipPointer[0] = skipStream[0].getFilePointer();
-  }
-
-  /**
-   * Subclasses must implement the actual skip data encoding in this method.
-   *
-   * @param level the level skip data shall be read from
-   * @param skipStream the skip stream to read from
-   */
-  protected abstract int readSkipData(int level, IndexInput skipStream) throws IOException;
-
-  /**
-   * read the length of the current level written via {@link
-   * MultiLevelSkipListWriter#writeLevelLength(long, IndexOutput)}.
-   *
-   * @param skipStream the IndexInput the length shall be read from
-   * @return level length
-   */
-  protected long readLevelLength(IndexInput skipStream) throws IOException {
-    return skipStream.readVLong();
-  }
-
-  /**
-   * read the child pointer written via {@link MultiLevelSkipListWriter#writeChildPointer(long,
-   * DataOutput)}.
-   *
-   * @param skipStream the IndexInput the child pointer shall be read from
-   * @return child pointer
-   */
-  protected long readChildPointer(IndexInput skipStream) throws IOException {
-    return skipStream.readVLong();
-  }
-
-  /** Copies the values of the last read skip entry on this level */
-  protected void setLastSkipData(int level) {
-    lastDoc = skipDoc[level];
-    lastChildPointer = childPointer[level];
-  }
-}

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/Placeholder.java

@@ -0,0 +1,23 @@
+/*
+ * 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;
+
+/** Remove this file when adding back compat codecs */
+public class Placeholder {
+  // no instance
+  private Placeholder() {}
+}

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene50/Lucene50SkipReader.java

@@ -20,7 +20,7 @@ import static org.apache.lucene.backward_codecs.lucene50.Lucene50PostingsFormat.
 
 import java.io.IOException;
 import java.util.Arrays;
-import org.apache.lucene.backward_codecs.Lucene50MultiLevelSkipListReader;
+import org.apache.lucene.codecs.MultiLevelSkipListReader;
 import org.apache.lucene.store.IndexInput;
 
 /**
@@ -50,7 +50,7 @@ import org.apache.lucene.store.IndexInput;
  *
  * <p>Therefore, we'll trim df before passing it to the interface. see trim(int)
  */
-class Lucene50SkipReader extends Lucene50MultiLevelSkipListReader {
+class Lucene50SkipReader extends MultiLevelSkipListReader {
   private final int version;
   private long[] docPointer;
   private long[] posPointer;
@@ -124,7 +124,7 @@ class Lucene50SkipReader extends Lucene50MultiLevelSkipListReader {
 
   /**
    * Returns the doc pointer of the doc to which the last call of {@link
-   * Lucene50MultiLevelSkipListReader#skipTo(int)} has skipped.
+   * MultiLevelSkipListReader#skipTo(int)} has skipped.
    */
   public long getDocPointer() {
     return lastDocPointer;

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene84/Lucene84SkipReader.java

@@ -18,7 +18,7 @@ package org.apache.lucene.backward_codecs.lucene84;
 
 import java.io.IOException;
 import java.util.Arrays;
-import org.apache.lucene.backward_codecs.Lucene50MultiLevelSkipListReader;
+import org.apache.lucene.codecs.MultiLevelSkipListReader;
 import org.apache.lucene.store.IndexInput;
 
 /**
@@ -48,7 +48,7 @@ import org.apache.lucene.store.IndexInput;
  *
  * <p>Therefore, we'll trim df before passing it to the interface. see trim(int)
  */
-class Lucene84SkipReader extends Lucene50MultiLevelSkipListReader {
+class Lucene84SkipReader extends MultiLevelSkipListReader {
   private long[] docPointer;
   private long[] posPointer;
   private long[] payPointer;
@@ -119,7 +119,7 @@ class Lucene84SkipReader extends Lucene50MultiLevelSkipListReader {
 
   /**
    * Returns the doc pointer of the doc to which the last call of {@link
-   * Lucene50MultiLevelSkipListReader#skipTo(int)} has skipped.
+   * MultiLevelSkipListReader#skipTo(int)} has skipped.
    */
   public long getDocPointer() {
     return lastDocPointer;

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene90/Lucene90SkipReader.java

@@ -18,7 +18,7 @@ package org.apache.lucene.backward_codecs.lucene90;
 
 import java.io.IOException;
 import java.util.Arrays;
-import org.apache.lucene.backward_codecs.Lucene50MultiLevelSkipListReader;
+import org.apache.lucene.codecs.MultiLevelSkipListReader;
 import org.apache.lucene.store.IndexInput;
 
 /**
@@ -48,7 +48,7 @@ import org.apache.lucene.store.IndexInput;
  *
  * <p>Therefore, we'll trim df before passing it to the interface. see trim(int)
  */
-class Lucene90SkipReader extends Lucene50MultiLevelSkipListReader {
+class Lucene90SkipReader extends MultiLevelSkipListReader {
   private long[] docPointer;
   private long[] posPointer;
   private long[] payPointer;
@@ -119,7 +119,7 @@ class Lucene90SkipReader extends Lucene50MultiLevelSkipListReader {
 
   /**
    * Returns the doc pointer of the doc to which the last call of {@link
-   * Lucene50MultiLevelSkipListReader#skipTo(int)} has skipped.
+   * MultiLevelSkipListReader#skipTo(int)} has skipped.
    */
   public long getDocPointer() {
     return lastDocPointer;

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

@@ -284,7 +284,7 @@ class SimpleTextFieldsReader extends FieldsProducer {
 
     // for skip list data
     private SimpleTextSkipReader skipReader;
-    private int nextSkipDoc = -1;
+    private int nextSkipDoc = 0;
     private long seekTo = -1;
 
     public SimpleTextDocsEnum() {
@@ -305,7 +305,7 @@ class SimpleTextFieldsReader extends FieldsProducer {
       tf = 1;
       cost = docFreq;
       skipReader.reset(skipPointer, docFreq);
-      nextSkipDoc = -1;
+      nextSkipDoc = 0;
       seekTo = -1;
       return this;
     }
@@ -458,7 +458,7 @@ class SimpleTextFieldsReader extends FieldsProducer {
 
     // for skip list data
     private SimpleTextSkipReader skipReader;
-    private int nextSkipDoc = -1;
+    private int nextSkipDoc = 0;
     private long seekTo = -1;
 
     public SimpleTextPostingsEnum() {
@@ -484,7 +484,7 @@ class SimpleTextFieldsReader extends FieldsProducer {
       }
       cost = docFreq;
       skipReader.reset(skipPointer, docFreq);
-      nextSkipDoc = -1;
+      nextSkipDoc = 0;
       seekTo = -1;
       return this;
     }

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

@@ -31,7 +31,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
-import org.apache.lucene.codecs.Lucene99MultiLevelSkipListReader;
+import org.apache.lucene.codecs.MultiLevelSkipListReader;
 import org.apache.lucene.index.Impact;
 import org.apache.lucene.index.Impacts;
 import org.apache.lucene.search.DocIdSetIterator;
@@ -51,7 +51,7 @@ import org.apache.lucene.util.StringHelper;
  *
  * @lucene.experimental
  */
-class SimpleTextSkipReader extends Lucene99MultiLevelSkipListReader {
+class SimpleTextSkipReader extends MultiLevelSkipListReader {
 
   private final CharsRefBuilder scratchUTF16 = new CharsRefBuilder();
   private final BytesRefBuilder scratch = new BytesRefBuilder();

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

@@ -41,7 +41,7 @@ class SimpleTextSkipWriter extends MultiLevelSkipListWriter {
 
   static final int BLOCK_SIZE = 8;
   private Map<Integer, Boolean> wroteHeaderPerLevelMap = new HashMap<>();
-  private int curDoc = -1;
+  private int curDoc;
   private long curDocFilePointer;
   private CompetitiveImpactAccumulator[] curCompetitiveFreqNorms;
   private final BytesRefBuilder scratch = new BytesRefBuilder();

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

@@ -35,7 +35,7 @@ import org.apache.lucene.util.MathUtil;
  *
  * @lucene.experimental
  */
-public abstract class Lucene99MultiLevelSkipListReader implements Closeable {
+public abstract class MultiLevelSkipListReader implements Closeable {
   /** the maximum number of skip levels possible for this index */
   protected int maxNumberOfSkipLevels;
 
@@ -63,7 +63,7 @@ public abstract class Lucene99MultiLevelSkipListReader implements Closeable {
   protected int[] skipDoc;
 
   /** Doc id of last read skip entry with docId <= target. */
-  private int lastDoc = -1;
+  private int lastDoc;
 
   /** Child pointer of current skip entry per level. */
   private long[] childPointer;
@@ -74,7 +74,7 @@ public abstract class Lucene99MultiLevelSkipListReader implements Closeable {
   private final int skipMultiplier;
 
   /** Creates a {@code MultiLevelSkipListReader}. */
-  protected Lucene99MultiLevelSkipListReader(
+  protected MultiLevelSkipListReader(
       IndexInput skipStream, int maxSkipLevels, int skipInterval, int skipMultiplier) {
     this.skipStream = new IndexInput[maxSkipLevels];
     this.skipPointer = new long[maxSkipLevels];
@@ -96,8 +96,7 @@ public abstract class Lucene99MultiLevelSkipListReader implements Closeable {
    * Creates a {@code MultiLevelSkipListReader}, where {@code skipInterval} and {@code
    * skipMultiplier} are the same.
    */
-  protected Lucene99MultiLevelSkipListReader(
+  protected MultiLevelSkipListReader(IndexInput skipStream, int maxSkipLevels, int skipInterval) {
-      IndexInput skipStream, int maxSkipLevels, int skipInterval) {
     this(skipStream, maxSkipLevels, skipInterval, skipInterval);
   }
 
@@ -187,7 +186,7 @@ public abstract class Lucene99MultiLevelSkipListReader implements Closeable {
     this.docCount = df;
     assert skipPointer >= 0 && skipPointer <= skipStream[0].length()
         : "invalid skip pointer: " + skipPointer + ", length=" + skipStream[0].length();
-    Arrays.fill(skipDoc, -1);
+    Arrays.fill(skipDoc, 0);
     Arrays.fill(numSkipped, 0);
     Arrays.fill(childPointer, 0);
 

lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99PostingsReader.java

@@ -334,7 +334,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
     private long totalTermFreq; // sum of freqBuffer in this posting list (or docFreq when omitted)
     private int blockUpto; // number of docs in or before the current block
     private int doc; // doc we last read
-    private int accum; // accumulator for doc deltas
+    private long accum; // accumulator for doc deltas
 
     // Where this term's postings start in the .doc file:
     private long docTermStartFP;
@@ -344,6 +344,10 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
     // no skip data for this term):
     private long skipOffset;
 
+    // docID for next skip point, we won't use skipper if
+    // target docID is not larger than this
+    private int nextSkipDoc;
+
     private boolean needsFreq; // true if the caller actually needs frequencies
     // as we read freqBuffer lazily, isFreqsRead shows if freqBuffer are read for the current block
     // always true when we don't have freqBuffer (indexHasFreq=false) or don't need freqBuffer
@@ -400,8 +404,9 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
           freqBuffer[i] = 1;
         }
       }
-      accum = -1;
+      accum = 0;
       blockUpto = 0;
+      nextSkipDoc = BLOCK_SIZE - 1; // we won't skip if target is found in first block
       docBufferUpto = BLOCK_SIZE;
       skipped = false;
       return this;
@@ -462,22 +467,20 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
             pforUtil.skip(docIn); // skip over freqBuffer if we don't need them at all
           }
         }
-        accum = (int) docBuffer[BLOCK_SIZE - 1];
         blockUpto += BLOCK_SIZE;
       } else if (docFreq == 1) {
         docBuffer[0] = singletonDocID;
         freqBuffer[0] = totalTermFreq;
         docBuffer[1] = NO_MORE_DOCS;
-        accum = NO_MORE_DOCS;
         blockUpto++;
       } else {
         // Read vInts:
         readVIntBlock(docIn, docBuffer, freqBuffer, left, indexHasFreq, needsFreq);
         prefixSum(docBuffer, left, accum);
         docBuffer[left] = NO_MORE_DOCS;
-        accum = NO_MORE_DOCS;
         blockUpto += left;
       }
+      accum = docBuffer[BLOCK_SIZE - 1];
       docBufferUpto = 0;
       assert docBuffer[BLOCK_SIZE] == NO_MORE_DOCS;
     }
@@ -498,7 +501,8 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
     public int advance(int target) throws IOException {
       // current skip docID < docIDs generated from current buffer <= next skip docID
       // we don't need to skip if target is buffered already
-      if (docFreq > BLOCK_SIZE && target > accum) {
+      if (docFreq > BLOCK_SIZE && target > nextSkipDoc) {
+
         if (skipper == null) {
           // Lazy init: first time this enum has ever been used for skipping
           skipper =
@@ -532,15 +536,28 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
           // as we have already positioned docIn where in needs to be.
           isFreqsRead = true;
         }
+        // next time we call advance, this is used to
+        // foresee whether skipper is necessary.
+        nextSkipDoc = skipper.getNextSkipDoc();
       }
       if (docBufferUpto == BLOCK_SIZE) {
         refillDocs();
       }
 
-      int next = findFirstGreater(docBuffer, target, docBufferUpto);
+      // Now scan... this is an inlined/pared down version
-      this.doc = (int) docBuffer[next];
+      // of nextDoc():
-      docBufferUpto = next + 1;
+      long doc;
-      return doc;
+      while (true) {
+        doc = docBuffer[docBufferUpto];
+
+        if (doc >= target) {
+          break;
+        }
+        ++docBufferUpto;
+      }
+
+      docBufferUpto++;
+      return this.doc = (int) doc;
     }
 
     @Override
@@ -592,7 +609,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
     private long totalTermFreq; // number of positions in this posting list
     private int blockUpto; // number of docs in or before the current block
     private int doc; // doc we last read
-    private int accum; // accumulator for doc deltas
+    private long accum; // accumulator for doc deltas
     private int freq; // freq we last read
     private int position; // current position
 
@@ -628,6 +645,8 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
     // no skip data for this term):
     private long skipOffset;
 
+    private int nextSkipDoc;
+
     private boolean needsOffsets; // true if we actually need offsets
     private boolean needsPayloads; // true if we actually need payloads
     private int singletonDocID; // docid when there is a single pulsed posting, otherwise -1
@@ -713,8 +732,13 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
       this.needsPayloads = PostingsEnum.featureRequested(flags, PostingsEnum.PAYLOADS);
 
       doc = -1;
-      accum = -1;
+      accum = 0;
       blockUpto = 0;
+      if (docFreq > BLOCK_SIZE) {
+        nextSkipDoc = BLOCK_SIZE - 1; // we won't skip if target is found in first block
+      } else {
+        nextSkipDoc = NO_MORE_DOCS; // not enough docs for skipping
+      }
       docBufferUpto = BLOCK_SIZE;
       skipped = false;
       return this;
@@ -737,21 +761,19 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
       if (left >= BLOCK_SIZE) {
         forDeltaUtil.decodeAndPrefixSum(docIn, accum, docBuffer);
         pforUtil.decode(docIn, freqBuffer);
-        accum = (int) docBuffer[BLOCK_SIZE - 1];
         blockUpto += BLOCK_SIZE;
       } else if (docFreq == 1) {
         docBuffer[0] = singletonDocID;
         freqBuffer[0] = totalTermFreq;
         docBuffer[1] = NO_MORE_DOCS;
-        accum = NO_MORE_DOCS;
         blockUpto++;
       } else {
         readVIntBlock(docIn, docBuffer, freqBuffer, left, true, true);
         prefixSum(docBuffer, left, accum);
         docBuffer[left] = NO_MORE_DOCS;
-        accum = NO_MORE_DOCS;
         blockUpto += left;
       }
+      accum = docBuffer[BLOCK_SIZE - 1];
       docBufferUpto = 0;
       assert docBuffer[BLOCK_SIZE] == NO_MORE_DOCS;
     }
@@ -845,7 +867,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
 
     @Override
     public int advance(int target) throws IOException {
-      if (docFreq > BLOCK_SIZE && target > accum) {
+      if (target > nextSkipDoc) {
         if (skipper == null) {
           // Lazy init: first time this enum has ever been used for skipping
           skipper =
@@ -879,6 +901,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
           lastStartOffset = 0; // new document
           payloadByteUpto = skipper.getPayloadByteUpto();
         }
+        nextSkipDoc = skipper.getNextSkipDoc();
       }
       if (docBufferUpto == BLOCK_SIZE) {
         refillDocs();
@@ -886,12 +909,16 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
 
       // Now scan:
       long doc;
-      do {
+      while (true) {
         doc = docBuffer[docBufferUpto];
         freq = (int) freqBuffer[docBufferUpto];
         posPendingCount += freq;
         docBufferUpto++;
-      } while (doc < target);
+
+        if (doc >= target) {
+          break;
+        }
+      }
 
       position = 0;
       lastStartOffset = 0;
@@ -1046,7 +1073,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
     private int docFreq; // number of docs in this posting list
     private int blockUpto; // number of documents in or before the current block
     private int doc; // doc we last read
-    private int accum; // accumulator for doc deltas
+    private long accum; // accumulator for doc deltas
 
     private int nextSkipDoc = -1;
 
@@ -1073,7 +1100,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
       docIn.seek(termState.docStartFP);
 
       doc = -1;
-      accum = -1;
+      accum = 0;
       blockUpto = 0;
       docBufferUpto = BLOCK_SIZE;
 
@@ -1126,15 +1153,14 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
         if (indexHasFreqs) {
           isFreqsRead = false;
         }
-        accum = (int) docBuffer[BLOCK_SIZE - 1];
         blockUpto += BLOCK_SIZE;
       } else {
         readVIntBlock(docIn, docBuffer, freqBuffer, left, indexHasFreqs, true);
         prefixSum(docBuffer, left, accum);
         docBuffer[left] = NO_MORE_DOCS;
-        accum = NO_MORE_DOCS;
         blockUpto += left;
       }
+      accum = docBuffer[BLOCK_SIZE - 1];
       docBufferUpto = 0;
       assert docBuffer[BLOCK_SIZE] == NO_MORE_DOCS;
     }
@@ -1182,8 +1208,10 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
 
     @Override
     public int advance(int target) throws IOException {
-      if (target > accum) {
+      if (target > nextSkipDoc) {
         advanceShallow(target);
+      }
+      if (docBufferUpto == BLOCK_SIZE) {
         refillDocs();
       }
 
@@ -1243,7 +1271,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
     private long totalTermFreq; // number of positions in this posting list
     private int docUpto; // how many docs we've read
     private int doc; // doc we last read
-    private int accum; // accumulator for doc deltas
+    private long accum; // accumulator for doc deltas
     private int freq; // freq we last read
     private int position; // current position
 
@@ -1302,7 +1330,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
       }
 
       doc = -1;
-      accum = -1;
+      accum = 0;
       docUpto = 0;
       docBufferUpto = BLOCK_SIZE;
 
@@ -1334,14 +1362,12 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
       if (left >= BLOCK_SIZE) {
         forDeltaUtil.decodeAndPrefixSum(docIn, accum, docBuffer);
         pforUtil.decode(docIn, freqBuffer);
-        accum = (int) docBuffer[BLOCK_SIZE - 1];
       } else {
         readVIntBlock(docIn, docBuffer, freqBuffer, left, true, true);
         prefixSum(docBuffer, left, accum);
         docBuffer[left] = NO_MORE_DOCS;
-        accum = NO_MORE_DOCS;
       }
-
+      accum = docBuffer[BLOCK_SIZE - 1];
       docBufferUpto = 0;
     }
 
@@ -1413,8 +1439,10 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
 
     @Override
     public int advance(int target) throws IOException {
-      if (target > accum) {
+      if (target > nextSkipDoc) {
         advanceShallow(target);
+      }
+      if (docBufferUpto == BLOCK_SIZE) {
         refillDocs();
       }
 
@@ -1548,7 +1576,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
     private int docUpto; // how many docs we've read
     private int posDocUpTo; // for how many docs we've read positions, offsets, and payloads
     private int doc; // doc we last read
-    private int accum; // accumulator for doc deltas
+    private long accum; // accumulator for doc deltas
     private int position; // current position
 
     // how many positions "behind" we are; nextPosition must
@@ -1657,7 +1685,7 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
       }
 
       doc = -1;
-      accum = -1;
+      accum = 0;
       docUpto = 0;
       posDocUpTo = 0;
       isFreqsRead = true;
@@ -1724,14 +1752,12 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
           isFreqsRead =
               false; // freq block will be loaded lazily when necessary, we don't load it here
         }
-        accum = (int) docBuffer[BLOCK_SIZE - 1];
       } else {
         readVIntBlock(docIn, docBuffer, freqBuffer, left, indexHasFreq, true);
         prefixSum(docBuffer, left, accum);
         docBuffer[left] = NO_MORE_DOCS;
-        accum = NO_MORE_DOCS;
       }
-
+      accum = docBuffer[BLOCK_SIZE - 1];
       docBufferUpto = 0;
     }
 
@@ -1849,8 +1875,10 @@ public final class Lucene99PostingsReader extends PostingsReaderBase {
 
     @Override
     public int advance(int target) throws IOException {
-      if (target > accum) {
+      if (target > nextSkipDoc) {
         advanceShallow(target);
+      }
+      if (docBufferUpto == BLOCK_SIZE) {
         if (seekTo >= 0) {
           docIn.seek(seekTo);
           seekTo = -1;

lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99PostingsWriter.java

@@ -205,7 +205,7 @@ public final class Lucene99PostingsWriter extends PushPostingsWriterBase {
         payStartFP = payOut.getFilePointer();
       }
     }
-    lastDocID = -1;
+    lastDocID = 0;
     lastBlockDocID = -1;
     skipWriter.resetSkip();
     this.norms = norms;
@@ -369,7 +369,7 @@ public final class Lucene99PostingsWriter extends PushPostingsWriterBase {
     final int singletonDocID;
     if (state.docFreq == 1) {
       // pulse the singleton docid into the term dictionary, freq is implicitly totalTermFreq
-      singletonDocID = (int) docDeltaBuffer[0] - 1;
+      singletonDocID = (int) docDeltaBuffer[0];
     } else {
       singletonDocID = -1;
       // Group vInt encode the remaining doc deltas and freqs:
@@ -468,7 +468,7 @@ public final class Lucene99PostingsWriter extends PushPostingsWriterBase {
     state.lastPosBlockOffset = lastPosBlockOffset;
     docBufferUpto = 0;
     posBufferUpto = 0;
-    lastDocID = -1;
+    lastDocID = 0;
     docCount = 0;
   }
 

lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99SkipReader.java

@@ -18,7 +18,7 @@ package org.apache.lucene.codecs.lucene99;
 
 import java.io.IOException;
 import java.util.Arrays;
-import org.apache.lucene.codecs.Lucene99MultiLevelSkipListReader;
+import org.apache.lucene.codecs.MultiLevelSkipListReader;
 import org.apache.lucene.store.IndexInput;
 
 /**
@@ -48,7 +48,7 @@ import org.apache.lucene.store.IndexInput;
  *
  * <p>Therefore, we'll trim df before passing it to the interface. see trim(int)
  */
-public class Lucene99SkipReader extends Lucene99MultiLevelSkipListReader {
+public class Lucene99SkipReader extends MultiLevelSkipListReader {
   private long[] docPointer;
   private long[] posPointer;
   private long[] payPointer;
@@ -119,7 +119,7 @@ public class Lucene99SkipReader extends Lucene99MultiLevelSkipListReader {
 
   /**
    * Returns the doc pointer of the doc to which the last call of {@link
-   * Lucene99MultiLevelSkipListReader#skipTo(int)} has skipped.
+   * MultiLevelSkipListReader#skipTo(int)} has skipped.
    */
   public long getDocPointer() {
     return lastDocPointer;

lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99SkipWriter.java

@@ -131,7 +131,7 @@ public final class Lucene99SkipWriter extends MultiLevelSkipListWriter {
   private void initSkip() {
     if (!initialized) {
       super.resetSkip();
-      Arrays.fill(lastSkipDoc, -1);
+      Arrays.fill(lastSkipDoc, 0);
       Arrays.fill(lastSkipDocPointer, lastDocFP);
       if (fieldHasPositions) {
         Arrays.fill(lastSkipPosPointer, lastPosFP);