LUCENE-9705: Create Lucene90DocValuesFormat and Lucene90NormsFormat (#2392)

For now these are just copies of Lucene80DocValuesFormat and
Lucene80NormsFormat. The existing formats were moved to backwards-codecs.

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene60/Lucene60FieldInfosFormat.java

@@ -314,7 +314,7 @@ public final class Lucene60FieldInfosFormat extends FieldInfosFormat {
   /**
    * Note: although this format is only used on older versions, we need to keep the write logic in
    * addition to the read logic. It's possible for field infos on older segments to be written to,
-   * for example as part of in-place doc values updates.
+   * for example as part of doc values updates.
    */
   @Override
   public void write(

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene80/IndexedDISI.java

@@ -0,0 +1,708 @@
+/*
+ * 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.lucene80;
+
+import java.io.DataInput;
+import java.io.IOException;
+import org.apache.lucene.search.DocIdSetIterator;
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.store.IndexOutput;
+import org.apache.lucene.store.RandomAccessInput;
+import org.apache.lucene.util.ArrayUtil;
+import org.apache.lucene.util.BitSetIterator;
+import org.apache.lucene.util.FixedBitSet;
+import org.apache.lucene.util.RoaringDocIdSet;
+
+/**
+ * Disk-based implementation of a {@link DocIdSetIterator} which can return the index of the current
+ * document, i.e. the ordinal of the current document among the list of documents that this iterator
+ * can return. This is useful to implement sparse doc values by only having to encode values for
+ * documents that actually have a value.
+ *
+ * <p>Implementation-wise, this {@link DocIdSetIterator} is inspired of {@link RoaringDocIdSet
+ * roaring bitmaps} and encodes ranges of {@code 65536} documents independently and picks between 3
+ * encodings depending on the density of the range:
+ *
+ * <ul>
+ *   <li>{@code ALL} if the range contains 65536 documents exactly,
+ *   <li>{@code DENSE} if the range contains 4096 documents or more; in that case documents are
+ *       stored in a bit set,
+ *   <li>{@code SPARSE} otherwise, and the lower 16 bits of the doc IDs are stored in a {@link
+ *       DataInput#readShort() short}.
+ * </ul>
+ *
+ * <p>Only ranges that contain at least one value are encoded.
+ *
+ * <p>This implementation uses 6 bytes per document in the worst-case, which happens in the case
+ * that all ranges contain exactly one document.
+ *
+ * <p>To avoid O(n) lookup time complexity, with n being the number of documents, two lookup tables
+ * are used: A lookup table for block offset and index, and a rank structure for DENSE block index
+ * lookups.
+ *
+ * <p>The lookup table is an array of {@code int}-pairs, with a pair for each block. It allows for
+ * direct jumping to the block, as opposed to iteration from the current position and forward one
+ * block at a time.
+ *
+ * <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.
+ *
+ * <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
+ * overflow (2^16 bytes if the int is treated as unsigned). This is currently the case, with the
+ * largest block being DENSE and using 2^13 + 36 bytes.
+ *
+ * <p>The cache overhead is numDocs/1024 bytes.
+ *
+ * <p>Note: There are 4 types of blocks: ALL, DENSE, SPARSE and non-existing (0 set bits). In the
+ * case of non-existing blocks, the entry in the lookup table has index equal to the previous entry
+ * and offset equal to the next non-empty block.
+ *
+ * <p>The block lookup table is stored at the end of the total block structure.
+ *
+ * <p>The rank structure for DENSE blocks is an array of byte-pairs with an entry for each sub-block
+ * (default 512 bits) out of the 65536 bits in the outer DENSE block.
+ *
+ * <p>Each rank-entry states the number of set bits within the block up to the bit before the bit
+ * positioned at the start of the sub-block. Note that that the rank entry of the first sub-block is
+ * always 0 and that the last entry can at most be 65536-2 = 65634 and thus will always fit into an
+ * byte-pair of 16 bits.
+ *
+ * <p>The rank structure for a given DENSE block is stored at the beginning of the DENSE block. This
+ * ensures locality and keeps logistics simple.
+ *
+ * @lucene.internal
+ */
+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
+  // two PackedInts or two MonotonicDirectReaders.
+  // The DENSE ranks (default 128 shorts = 256 bytes) could likewise be compressed. But as there is
+  // at least 4096 set bits in DENSE blocks, there will be at least one rank with 2^12 bits, so it
+  // is doubtful if there is much to gain here.
+
+  private static final int BLOCK_SIZE =
+      65536; // The number of docIDs that a single block represents
+
+  private static final int DENSE_BLOCK_LONGS = BLOCK_SIZE / Long.SIZE; // 1024
+  public static final byte DEFAULT_DENSE_RANK_POWER = 9; // Every 512 docIDs / 8 longs
+
+  static final int MAX_ARRAY_LENGTH = (1 << 12) - 1;
+
+  private static void flush(
+      int block, FixedBitSet buffer, int cardinality, byte denseRankPower, IndexOutput out)
+      throws IOException {
+    assert block >= 0 && block < 65536;
+    out.writeShort((short) block);
+    assert cardinality > 0 && cardinality <= 65536;
+    out.writeShort((short) (cardinality - 1));
+    if (cardinality > MAX_ARRAY_LENGTH) {
+      if (cardinality != 65536) { // all docs are set
+        if (denseRankPower != -1) {
+          final byte[] rank = createRank(buffer, denseRankPower);
+          out.writeBytes(rank, rank.length);
+        }
+        for (long word : buffer.getBits()) {
+          out.writeLong(word);
+        }
+      }
+    } else {
+      BitSetIterator it = new BitSetIterator(buffer, cardinality);
+      for (int doc = it.nextDoc(); doc != DocIdSetIterator.NO_MORE_DOCS; doc = it.nextDoc()) {
+        out.writeShort((short) doc);
+      }
+    }
+  }
+
+  // Creates a DENSE rank-entry (the number of set bits up to a given point) for the buffer.
+  // One rank-entry for every {@code 2^denseRankPower} bits, with each rank-entry using 2 bytes.
+  // Represented as a byte[] for fast flushing and mirroring of the retrieval representation.
+  private static byte[] createRank(FixedBitSet buffer, byte denseRankPower) {
+    final int longsPerRank = 1 << (denseRankPower - 6);
+    final int rankMark = longsPerRank - 1;
+    final int rankIndexShift = denseRankPower - 7; // 6 for the long (2^6) + 1 for 2 bytes/entry
+    final byte[] rank = new byte[DENSE_BLOCK_LONGS >> rankIndexShift];
+    final long[] bits = buffer.getBits();
+    int bitCount = 0;
+    for (int word = 0; word < DENSE_BLOCK_LONGS; word++) {
+      if ((word & rankMark) == 0) { // Every longsPerRank longs
+        rank[word >> rankIndexShift] = (byte) (bitCount >> 8);
+        rank[(word >> rankIndexShift) + 1] = (byte) (bitCount & 0xFF);
+      }
+      bitCount += Long.bitCount(bits[word]);
+    }
+    return rank;
+  }
+
+  /**
+   * Writes the docIDs from it to out, in logical blocks, one for each 65536 docIDs in monotonically
+   * increasing gap-less order. DENSE blocks uses {@link #DEFAULT_DENSE_RANK_POWER} of 9 (every 512
+   * docIDs / 8 longs). The caller must keep track of the number of jump-table entries (returned by
+   * this method) as well as the denseRankPower (9 for this method) and provide them when
+   * constructing an IndexedDISI for reading.
+   *
+   * @param it the document IDs.
+   * @param out destination for the blocks.
+   * @throws IOException if there was an error writing to out.
+   * @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) throws IOException {
+    return writeBitSet(it, out, DEFAULT_DENSE_RANK_POWER);
+  }
+
+  /**
+   * Writes the docIDs from it to out, in logical blocks, one for each 65536 docIDs in monotonically
+   * increasing gap-less order. The caller must keep track of the number of jump-table entries
+   * (returned by this method) as well as the denseRankPower and provide them when constructing an
+   * IndexedDISI for reading.
+   *
+   * @param it the document IDs.
+   * @param out destination for the blocks.
+   * @param denseRankPower for {@link Method#DENSE} blocks, a rank will be written every {@code
+   *     2^denseRankPower} docIDs. Values &lt; 7 (every 128 docIDs) or &gt; 15 (every 32768 docIDs)
+   *     disables DENSE rank. Recommended values are 8-12: Every 256-4096 docIDs or 4-64 longs.
+   *     {@link #DEFAULT_DENSE_RANK_POWER} is 9: Every 512 docIDs. This should be stored in meta and
+   *     used when creating an instance of IndexedDISI.
+   * @throws IOException if there was an error writing to out.
+   * @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)
+      throws IOException {
+    final long origo = out.getFilePointer(); // All jumps are relative to the origo
+    if ((denseRankPower < 7 || denseRankPower > 15) && denseRankPower != -1) {
+      throw new IllegalArgumentException(
+          "Acceptable values for denseRankPower are 7-15 (every 128-32768 docIDs). "
+              + "The provided power was "
+              + denseRankPower
+              + " (every "
+              + (int) Math.pow(2, denseRankPower)
+              + " docIDs)");
+    }
+    int totalCardinality = 0;
+    int blockCardinality = 0;
+    final FixedBitSet buffer = new FixedBitSet(1 << 16);
+    int[] jumps = new int[ArrayUtil.oversize(1, Integer.BYTES * 2)];
+    int prevBlock = -1;
+    int jumpBlockIndex = 0;
+
+    for (int doc = it.nextDoc(); doc != DocIdSetIterator.NO_MORE_DOCS; doc = it.nextDoc()) {
+      final int block = doc >>> 16;
+      if (prevBlock != -1 && block != prevBlock) {
+        // Track offset+index from previous block up to current
+        jumps =
+            addJumps(
+                jumps,
+                out.getFilePointer() - origo,
+                totalCardinality,
+                jumpBlockIndex,
+                prevBlock + 1);
+        jumpBlockIndex = prevBlock + 1;
+        // Flush block
+        flush(prevBlock, buffer, blockCardinality, denseRankPower, out);
+        // Reset for next block
+        buffer.clear(0, buffer.length());
+        totalCardinality += blockCardinality;
+        blockCardinality = 0;
+      }
+      buffer.set(doc & 0xFFFF);
+      blockCardinality++;
+      prevBlock = block;
+    }
+    if (blockCardinality > 0) {
+      jumps =
+          addJumps(
+              jumps, out.getFilePointer() - origo, totalCardinality, jumpBlockIndex, prevBlock + 1);
+      totalCardinality += blockCardinality;
+      flush(prevBlock, buffer, blockCardinality, denseRankPower, out);
+      buffer.clear(0, buffer.length());
+      prevBlock++;
+    }
+    final int lastBlock =
+        prevBlock == -1 ? 0 : prevBlock; // There will always be at least 1 block (NO_MORE_DOCS)
+    // Last entry is a SPARSE with blockIndex == 32767 and the single entry 65535, which becomes the
+    // docID NO_MORE_DOCS
+    // To avoid creating 65K jump-table entries, only a single entry is created pointing to the
+    // offset of the
+    // NO_MORE_DOCS block, with the jumpBlockIndex set to the logical EMPTY block after all real
+    // blocks.
+    jumps =
+        addJumps(jumps, out.getFilePointer() - origo, totalCardinality, lastBlock, lastBlock + 1);
+    buffer.set(DocIdSetIterator.NO_MORE_DOCS & 0xFFFF);
+    flush(DocIdSetIterator.NO_MORE_DOCS >>> 16, buffer, 1, denseRankPower, out);
+    // offset+index jump-table stored at the end
+    return flushBlockJumps(jumps, lastBlock + 1, out);
+  }
+
+  // Adds entries to the offset & index jump-table for blocks
+  private static int[] addJumps(int[] jumps, long offset, int index, int startBlock, int endBlock) {
+    assert offset < Integer.MAX_VALUE
+        : "Logically the offset should not exceed 2^30 but was >= Integer.MAX_VALUE";
+    jumps = ArrayUtil.grow(jumps, (endBlock + 1) * 2);
+    for (int b = startBlock; b < endBlock; b++) {
+      jumps[b * 2] = index;
+      jumps[b * 2 + 1] = (int) offset;
+    }
+    return jumps;
+  }
+
+  // Flushes the offset & index jump-table for blocks. This should be the last data written to out
+  // This method returns the blockCount for the blocks reachable for the jump_table or -1 for no
+  // jump-table
+  private static short flushBlockJumps(int[] jumps, int blockCount, IndexOutput out)
+      throws IOException {
+    if (blockCount
+        == 2) { // Jumps with a single real entry + NO_MORE_DOCS is just wasted space so we ignore
+      // that
+      blockCount = 0;
+    }
+    for (int i = 0; i < blockCount; i++) {
+      out.writeInt(jumps[i * 2]); // index
+      out.writeInt(jumps[i * 2 + 1]); // offset
+    }
+    // As there are at most 32k blocks, the count is a short
+    // The jumpTableOffset will be at lastPos - (blockCount * Long.BYTES)
+    return (short) blockCount;
+  }
+
+  // Members are pkg-private to avoid synthetic accessors when accessed from the `Method` enum
+
+  /** The slice that stores the {@link DocIdSetIterator}. */
+  final IndexInput slice;
+
+  final int jumpTableEntryCount;
+  final byte denseRankPower;
+  final RandomAccessInput jumpTable; // Skip blocks of 64K bits
+  final byte[] denseRankTable;
+  final long cost;
+
+  /**
+   * This constructor always creates a new blockSlice and a new jumpTable from in, to ensure that
+   * operations are independent from the caller. See {@link #IndexedDISI(IndexInput,
+   * RandomAccessInput, int, byte, long)} for re-use of blockSlice and jumpTable.
+   *
+   * @param in backing data.
+   * @param offset starting offset for blocks in the backing data.
+   * @param length the number of bytes holding blocks and jump-table in the backing data.
+   * @param jumpTableEntryCount the number of blocks covered by the jump-table. This must match the
+   *     number returned by {@link #writeBitSet(DocIdSetIterator, IndexOutput, byte)}.
+   * @param denseRankPower the number of docIDs covered by each rank entry in DENSE blocks,
+   *     expressed as {@code 2^denseRankPower}. This must match the power given in {@link
+   *     #writeBitSet(DocIdSetIterator, IndexOutput, byte)}
+   * @param cost normally the number of logical docIDs.
+   */
+  IndexedDISI(
+      IndexInput in,
+      long offset,
+      long length,
+      int jumpTableEntryCount,
+      byte denseRankPower,
+      long cost)
+      throws IOException {
+    this(
+        createBlockSlice(in, "docs", offset, length, jumpTableEntryCount),
+        createJumpTable(in, offset, length, jumpTableEntryCount),
+        jumpTableEntryCount,
+        denseRankPower,
+        cost);
+  }
+
+  /**
+   * This constructor allows to pass the slice and jumpTable directly in case it helps reuse. see
+   * eg. Lucene80 norms producer's merge instance.
+   *
+   * @param blockSlice data blocks, normally created by {@link #createBlockSlice}.
+   * @param jumpTable table holding jump-data for block-skips, normally created by {@link
+   *     #createJumpTable}.
+   * @param jumpTableEntryCount the number of blocks covered by the jump-table. This must match the
+   *     number returned by {@link #writeBitSet(DocIdSetIterator, IndexOutput, byte)}.
+   * @param denseRankPower the number of docIDs covered by each rank entry in DENSE blocks,
+   *     expressed as {@code 2^denseRankPower}. This must match the power given in {@link
+   *     #writeBitSet(DocIdSetIterator, IndexOutput, byte)}
+   * @param cost normally the number of logical docIDs.
+   */
+  IndexedDISI(
+      IndexInput blockSlice,
+      RandomAccessInput jumpTable,
+      int jumpTableEntryCount,
+      byte denseRankPower,
+      long cost)
+      throws IOException {
+    if ((denseRankPower < 7 || denseRankPower > 15) && denseRankPower != -1) {
+      throw new IllegalArgumentException(
+          "Acceptable values for denseRankPower are 7-15 (every 128-32768 docIDs). "
+              + "The provided power was "
+              + denseRankPower
+              + " (every "
+              + (int) Math.pow(2, denseRankPower)
+              + " docIDs). ");
+    }
+
+    this.slice = blockSlice;
+    this.jumpTable = jumpTable;
+    this.jumpTableEntryCount = jumpTableEntryCount;
+    this.denseRankPower = denseRankPower;
+    final int rankIndexShift = denseRankPower - 7;
+    this.denseRankTable =
+        denseRankPower == -1 ? null : new byte[DENSE_BLOCK_LONGS >> rankIndexShift];
+    this.cost = cost;
+  }
+
+  /**
+   * Helper method for using {@link #IndexedDISI(IndexInput, RandomAccessInput, int, byte, long)}.
+   * Creates a disiSlice for the IndexedDISI data blocks, without the jump-table.
+   *
+   * @param slice backing data, holding both blocks and jump-table.
+   * @param sliceDescription human readable slice designation.
+   * @param offset relative to the backing data.
+   * @param length full length of the IndexedDISI, including blocks and jump-table data.
+   * @param jumpTableEntryCount the number of blocks covered by the jump-table.
+   * @return a jumpTable containing the block jump-data or null if no such table exists.
+   * @throws IOException if a RandomAccessInput could not be created from slice.
+   */
+  public static IndexInput createBlockSlice(
+      IndexInput slice, String sliceDescription, long offset, long length, int jumpTableEntryCount)
+      throws IOException {
+    long jumpTableBytes = jumpTableEntryCount < 0 ? 0 : jumpTableEntryCount * Integer.BYTES * 2;
+    return slice.slice(sliceDescription, offset, length - jumpTableBytes);
+  }
+
+  /**
+   * Helper method for using {@link #IndexedDISI(IndexInput, RandomAccessInput, int, byte, long)}.
+   * Creates a RandomAccessInput covering only the jump-table data or null.
+   *
+   * @param slice backing data, holding both blocks and jump-table.
+   * @param offset relative to the backing data.
+   * @param length full length of the IndexedDISI, including blocks and jump-table data.
+   * @param jumpTableEntryCount the number of blocks covered by the jump-table.
+   * @return a jumpTable containing the block jump-data or null if no such table exists.
+   * @throws IOException if a RandomAccessInput could not be created from slice.
+   */
+  public static RandomAccessInput createJumpTable(
+      IndexInput slice, long offset, long length, int jumpTableEntryCount) throws IOException {
+    if (jumpTableEntryCount <= 0) {
+      return null;
+    } else {
+      int jumpTableBytes = jumpTableEntryCount * Integer.BYTES * 2;
+      return slice.randomAccessSlice(offset + length - jumpTableBytes, jumpTableBytes);
+    }
+  }
+
+  int block = -1;
+  long blockEnd;
+  long denseBitmapOffset = -1; // Only used for DENSE blocks
+  int nextBlockIndex = -1;
+  Method method;
+
+  int doc = -1;
+  int index = -1;
+
+  // SPARSE variables
+  boolean exists;
+
+  // DENSE variables
+  long word;
+  int wordIndex = -1;
+  // number of one bits encountered so far, including those of `word`
+  int numberOfOnes;
+  // Used with rank for jumps inside of DENSE as they are absolute instead of relative
+  int denseOrigoIndex;
+
+  // ALL variables
+  int gap;
+
+  @Override
+  public int docID() {
+    return doc;
+  }
+
+  @Override
+  public int advance(int target) throws IOException {
+    final int targetBlock = target & 0xFFFF0000;
+    if (block < targetBlock) {
+      advanceBlock(targetBlock);
+    }
+    if (block == targetBlock) {
+      if (method.advanceWithinBlock(this, target)) {
+        return doc;
+      }
+      readBlockHeader();
+    }
+    boolean found = method.advanceWithinBlock(this, block);
+    assert found;
+    return doc;
+  }
+
+  public boolean advanceExact(int target) throws IOException {
+    final int targetBlock = target & 0xFFFF0000;
+    if (block < targetBlock) {
+      advanceBlock(targetBlock);
+    }
+    boolean found = block == targetBlock && method.advanceExactWithinBlock(this, target);
+    this.doc = target;
+    return found;
+  }
+
+  private void advanceBlock(int targetBlock) throws IOException {
+    final int blockIndex = targetBlock >> 16;
+    // If the destination block is 2 blocks or more ahead, we use the jump-table.
+    if (jumpTable != null && blockIndex >= (block >> 16) + 2) {
+      // If the jumpTableEntryCount is exceeded, there are no further bits. Last entry is always
+      // NO_MORE_DOCS
+      final int inRangeBlockIndex =
+          blockIndex < jumpTableEntryCount ? blockIndex : jumpTableEntryCount - 1;
+      final int index = jumpTable.readInt(inRangeBlockIndex * Integer.BYTES * 2);
+      final int offset = jumpTable.readInt(inRangeBlockIndex * Integer.BYTES * 2 + Integer.BYTES);
+      this.nextBlockIndex = index - 1; // -1 to compensate for the always-added 1 in readBlockHeader
+      slice.seek(offset);
+      readBlockHeader();
+      return;
+    }
+
+    // Fallback to iteration of blocks
+    do {
+      slice.seek(blockEnd);
+      readBlockHeader();
+    } while (block < targetBlock);
+  }
+
+  private void readBlockHeader() throws IOException {
+    block = Short.toUnsignedInt(slice.readShort()) << 16;
+    assert block >= 0;
+    final int numValues = 1 + Short.toUnsignedInt(slice.readShort());
+    index = nextBlockIndex;
+    nextBlockIndex = index + numValues;
+    if (numValues <= MAX_ARRAY_LENGTH) {
+      method = Method.SPARSE;
+      blockEnd = slice.getFilePointer() + (numValues << 1);
+    } else if (numValues == 65536) {
+      method = Method.ALL;
+      blockEnd = slice.getFilePointer();
+      gap = block - index - 1;
+    } else {
+      method = Method.DENSE;
+      denseBitmapOffset =
+          slice.getFilePointer() + (denseRankTable == null ? 0 : denseRankTable.length);
+      blockEnd = denseBitmapOffset + (1 << 13);
+      // Performance consideration: All rank (default 128 * 16 bits) are loaded up front. This
+      // should be fast with the
+      // reusable byte[] buffer, but it is still wasted if the DENSE block is iterated in small
+      // steps.
+      // If this results in too great a performance regression, a heuristic strategy might work
+      // where the rank data
+      // are loaded on first in-block advance, if said advance is > X docIDs. The hope being that a
+      // small first
+      // advance means that subsequent advances will be small too.
+      // Another alternative is to maintain an extra slice for DENSE rank, but IndexedDISI is
+      // already slice-heavy.
+      if (denseRankPower != -1) {
+        slice.readBytes(denseRankTable, 0, denseRankTable.length);
+      }
+      wordIndex = -1;
+      numberOfOnes = index + 1;
+      denseOrigoIndex = numberOfOnes;
+    }
+  }
+
+  @Override
+  public int nextDoc() throws IOException {
+    return advance(doc + 1);
+  }
+
+  public int index() {
+    return index;
+  }
+
+  @Override
+  public long cost() {
+    return cost;
+  }
+
+  enum Method {
+    SPARSE {
+      @Override
+      boolean advanceWithinBlock(IndexedDISI disi, int target) throws IOException {
+        final int targetInBlock = target & 0xFFFF;
+        // TODO: binary search
+        for (; disi.index < disi.nextBlockIndex; ) {
+          int doc = Short.toUnsignedInt(disi.slice.readShort());
+          disi.index++;
+          if (doc >= targetInBlock) {
+            disi.doc = disi.block | doc;
+            disi.exists = true;
+            return true;
+          }
+        }
+        return false;
+      }
+
+      @Override
+      boolean advanceExactWithinBlock(IndexedDISI disi, int target) throws IOException {
+        final int targetInBlock = target & 0xFFFF;
+        // TODO: binary search
+        if (target == disi.doc) {
+          return disi.exists;
+        }
+        for (; disi.index < disi.nextBlockIndex; ) {
+          int doc = Short.toUnsignedInt(disi.slice.readShort());
+          disi.index++;
+          if (doc >= targetInBlock) {
+            if (doc != targetInBlock) {
+              disi.index--;
+              disi.slice.seek(disi.slice.getFilePointer() - Short.BYTES);
+              break;
+            }
+            disi.exists = true;
+            return true;
+          }
+        }
+        disi.exists = false;
+        return false;
+      }
+    },
+    DENSE {
+      @Override
+      boolean advanceWithinBlock(IndexedDISI disi, int target) throws IOException {
+        final int targetInBlock = target & 0xFFFF;
+        final int targetWordIndex = targetInBlock >>> 6;
+
+        // If possible, skip ahead using the rank cache
+        // If the distance between the current position and the target is < rank-longs
+        // there is no sense in using rank
+        if (disi.denseRankPower != -1
+            && targetWordIndex - disi.wordIndex >= (1 << (disi.denseRankPower - 6))) {
+          rankSkip(disi, targetInBlock);
+        }
+
+        for (int i = disi.wordIndex + 1; i <= targetWordIndex; ++i) {
+          disi.word = disi.slice.readLong();
+          disi.numberOfOnes += Long.bitCount(disi.word);
+        }
+        disi.wordIndex = targetWordIndex;
+
+        long leftBits = disi.word >>> target;
+        if (leftBits != 0L) {
+          disi.doc = target + Long.numberOfTrailingZeros(leftBits);
+          disi.index = disi.numberOfOnes - Long.bitCount(leftBits);
+          return true;
+        }
+
+        // There were no set bits at the wanted position. Move forward until one is reached
+        while (++disi.wordIndex < 1024) {
+          // This could use the rank cache to skip empty spaces >= 512 bits, but it seems
+          // unrealistic
+          // that such blocks would be DENSE
+          disi.word = disi.slice.readLong();
+          if (disi.word != 0) {
+            disi.index = disi.numberOfOnes;
+            disi.numberOfOnes += Long.bitCount(disi.word);
+            disi.doc = disi.block | (disi.wordIndex << 6) | Long.numberOfTrailingZeros(disi.word);
+            return true;
+          }
+        }
+        // No set bits in the block at or after the wanted position.
+        return false;
+      }
+
+      @Override
+      boolean advanceExactWithinBlock(IndexedDISI disi, int target) throws IOException {
+        final int targetInBlock = target & 0xFFFF;
+        final int targetWordIndex = targetInBlock >>> 6;
+
+        // If possible, skip ahead using the rank cache
+        // If the distance between the current position and the target is < rank-longs
+        // there is no sense in using rank
+        if (disi.denseRankPower != -1
+            && targetWordIndex - disi.wordIndex >= (1 << (disi.denseRankPower - 6))) {
+          rankSkip(disi, targetInBlock);
+        }
+
+        for (int i = disi.wordIndex + 1; i <= targetWordIndex; ++i) {
+          disi.word = disi.slice.readLong();
+          disi.numberOfOnes += Long.bitCount(disi.word);
+        }
+        disi.wordIndex = targetWordIndex;
+
+        long leftBits = disi.word >>> target;
+        disi.index = disi.numberOfOnes - Long.bitCount(leftBits);
+        return (leftBits & 1L) != 0;
+      }
+    },
+    ALL {
+      @Override
+      boolean advanceWithinBlock(IndexedDISI disi, int target) {
+        disi.doc = target;
+        disi.index = target - disi.gap;
+        return true;
+      }
+
+      @Override
+      boolean advanceExactWithinBlock(IndexedDISI disi, int target) {
+        disi.index = target - disi.gap;
+        return true;
+      }
+    };
+
+    /**
+     * Advance to the first doc from the block that is equal to or greater than {@code target}.
+     * Return true if there is such a doc and false otherwise.
+     */
+    abstract boolean advanceWithinBlock(IndexedDISI disi, int target) throws IOException;
+
+    /**
+     * Advance the iterator exactly to the position corresponding to the given {@code target} and
+     * return whether this document exists.
+     */
+    abstract boolean advanceExactWithinBlock(IndexedDISI disi, int target) throws IOException;
+  }
+
+  /**
+   * If the distance between the current position and the target is > 8 words, the rank cache will
+   * be used to guarantee a worst-case of 1 rank-lookup and 7 word-read-and-count-bits operations.
+   * Note: This does not guarantee a skip up to target, only up to nearest rank boundary. It is the
+   * responsibility of the caller to iterate further to reach target.
+   *
+   * @param disi standard DISI.
+   * @param targetInBlock lower 16 bits of the target
+   * @throws IOException if a DISI seek failed.
+   */
+  private static void rankSkip(IndexedDISI disi, int targetInBlock) throws IOException {
+    assert disi.denseRankPower >= 0 : disi.denseRankPower;
+    // Resolve the rank as close to targetInBlock as possible (maximum distance is 8 longs)
+    // Note: rankOrigoOffset is tracked on block open, so it is absolute (e.g. don't add origo)
+    final int rankIndex =
+        targetInBlock >> disi.denseRankPower; // Default is 9 (8 longs: 2^3 * 2^6 = 512 docIDs)
+
+    final int rank =
+        (disi.denseRankTable[rankIndex << 1] & 0xFF) << 8
+            | (disi.denseRankTable[(rankIndex << 1) + 1] & 0xFF);
+
+    // Position the counting logic just after the rank point
+    final int rankAlignedWordIndex = rankIndex << disi.denseRankPower >> 6;
+    disi.slice.seek(disi.denseBitmapOffset + rankAlignedWordIndex * Long.BYTES);
+    long rankWord = disi.slice.readLong();
+    int denseNOO = rank + Long.bitCount(rankWord);
+
+    disi.wordIndex = rankAlignedWordIndex;
+    disi.word = rankWord;
+    disi.numberOfOnes = disi.denseOrigoIndex + denseNOO;
+  }
+}

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

@@ -35,7 +35,6 @@ import org.apache.lucene.codecs.StoredFieldsFormat;
 import org.apache.lucene.codecs.TermVectorsFormat;
 import org.apache.lucene.codecs.VectorFormat;
 import org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat;
-import org.apache.lucene.codecs.lucene80.Lucene80NormsFormat;
 import org.apache.lucene.codecs.perfield.PerFieldDocValuesFormat;
 import org.apache.lucene.codecs.perfield.PerFieldPostingsFormat;
 
@@ -44,7 +43,7 @@ import org.apache.lucene.codecs.perfield.PerFieldPostingsFormat;
  *
  * <p>
  *
- * @see org.apache.lucene.codecs.lucene80 package documentation for file format details.
+ * @see org.apache.lucene.backward_codecs.lucene80 package documentation for file format details.
  * @lucene.experimental
  */
 public class Lucene80Codec extends Codec {

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene80/Lucene80DocValuesConsumer.java

@@ -14,11 +14,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.backward_codecs.lucene80;
 
-import static org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat.DIRECT_MONOTONIC_BLOCK_SHIFT;
+import static org.apache.lucene.backward_codecs.lucene80.Lucene80DocValuesFormat.DIRECT_MONOTONIC_BLOCK_SHIFT;
-import static org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat.NUMERIC_BLOCK_SHIFT;
+import static org.apache.lucene.backward_codecs.lucene80.Lucene80DocValuesFormat.NUMERIC_BLOCK_SHIFT;
-import static org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat.NUMERIC_BLOCK_SIZE;
+import static org.apache.lucene.backward_codecs.lucene80.Lucene80DocValuesFormat.NUMERIC_BLOCK_SIZE;
 
 import java.io.Closeable;
 import java.io.IOException;
@@ -403,7 +403,7 @@ final class Lucene80DocValuesConsumer extends DocValuesConsumer implements Close
   }
 
   class CompressedBinaryBlockWriter implements Closeable {
-    final FastCompressionHashTable ht = new LZ4.FastCompressionHashTable();
+    final FastCompressionHashTable ht = new FastCompressionHashTable();
     int uncompressedBlockLength = 0;
     int maxUncompressedBlockLength = 0;
     int numDocsInCurrentBlock = 0;
@@ -772,10 +772,10 @@ final class Lucene80DocValuesConsumer extends DocValuesConsumer implements Close
     int maxLength = 0, maxBlockLength = 0;
     TermsEnum iterator = values.termsEnum();
 
-    LZ4.FastCompressionHashTable ht = null;
+    FastCompressionHashTable ht = null;
     ByteArrayDataOutput bufferedOutput = null;
     if (compress) {
-      ht = new LZ4.FastCompressionHashTable();
+      ht = new FastCompressionHashTable();
       bufferedOutput = new ByteArrayDataOutput(termsDictBuffer);
     }
 
@@ -840,7 +840,7 @@ final class Lucene80DocValuesConsumer extends DocValuesConsumer implements Close
   }
 
   private int compressAndGetTermsDictBlockLength(
-      ByteArrayDataOutput bufferedOutput, LZ4.FastCompressionHashTable ht) throws IOException {
+      ByteArrayDataOutput bufferedOutput, FastCompressionHashTable ht) throws IOException {
     int uncompressedLength = bufferedOutput.getPosition();
     data.writeVInt(uncompressedLength);
     long before = data.getFilePointer();

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene80/Lucene80DocValuesFormat.java

@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.backward_codecs.lucene80;
 
 import java.io.IOException;
 import java.util.Objects;
@@ -163,6 +163,11 @@ public final class Lucene80DocValuesFormat extends DocValuesFormat {
     this.mode = Objects.requireNonNull(mode);
   }
 
+  /**
+   * Note: although this format is only used on older versions, we need to keep the write logic in
+   * addition to the read logic. It's possible for doc values on older segments to be written to
+   * through doc values updates.
+   */
   @Override
   public DocValuesConsumer fieldsConsumer(SegmentWriteState state) throws IOException {
     return new Lucene80DocValuesConsumer(

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene80/Lucene80DocValuesProducer.java

@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.backward_codecs.lucene80;
 
 import java.io.Closeable;
 import java.io.IOException;

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene80/Lucene80NormsFormat.java

@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.backward_codecs.lucene80;
 
 import java.io.IOException;
 import org.apache.lucene.codecs.CodecUtil;
@@ -87,8 +87,7 @@ public class Lucene80NormsFormat extends NormsFormat {
 
   @Override
   public NormsConsumer normsConsumer(SegmentWriteState state) throws IOException {
-    return new Lucene80NormsConsumer(
+    throw new UnsupportedOperationException("Old codecs may only be used for reading");
-        state, DATA_CODEC, DATA_EXTENSION, METADATA_CODEC, METADATA_EXTENSION);
   }
 
   @Override
@@ -97,10 +96,10 @@ public class Lucene80NormsFormat extends NormsFormat {
         state, DATA_CODEC, DATA_EXTENSION, METADATA_CODEC, METADATA_EXTENSION);
   }
 
-  private static final String DATA_CODEC = "Lucene80NormsData";
+  static final String DATA_CODEC = "Lucene80NormsData";
-  private static final String DATA_EXTENSION = "nvd";
+  static final String DATA_EXTENSION = "nvd";
-  private static final String METADATA_CODEC = "Lucene80NormsMetadata";
+  static final String METADATA_CODEC = "Lucene80NormsMetadata";
-  private static final String METADATA_EXTENSION = "nvm";
+  static final String METADATA_EXTENSION = "nvm";
   static final int VERSION_START = 0;
   static final int VERSION_CURRENT = VERSION_START;
 }

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene80/Lucene80NormsProducer.java

@@ -14,10 +14,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.backward_codecs.lucene80;
 
-import static org.apache.lucene.codecs.lucene80.Lucene80NormsFormat.VERSION_CURRENT;
+import static org.apache.lucene.backward_codecs.lucene80.Lucene80NormsFormat.VERSION_CURRENT;
-import static org.apache.lucene.codecs.lucene80.Lucene80NormsFormat.VERSION_START;
+import static org.apache.lucene.backward_codecs.lucene80.Lucene80NormsFormat.VERSION_START;
 
 import java.io.IOException;
 import java.util.HashMap;

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

@@ -15,5 +15,5 @@
  * limitations under the License.
  */
 
-/** Lucene 8.0 file format. */
+/** Components from the Lucene 8.0 index format. */
 package org.apache.lucene.backward_codecs.lucene80;

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

@@ -24,6 +24,7 @@ import org.apache.lucene.backward_codecs.lucene50.Lucene50StoredFieldsFormat.Mod
 import org.apache.lucene.backward_codecs.lucene60.Lucene60FieldInfosFormat;
 import org.apache.lucene.backward_codecs.lucene60.Lucene60PointsFormat;
 import org.apache.lucene.backward_codecs.lucene70.Lucene70SegmentInfoFormat;
+import org.apache.lucene.backward_codecs.lucene80.Lucene80NormsFormat;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.CompoundFormat;
 import org.apache.lucene.codecs.DocValuesFormat;
@@ -38,7 +39,6 @@ import org.apache.lucene.codecs.StoredFieldsFormat;
 import org.apache.lucene.codecs.TermVectorsFormat;
 import org.apache.lucene.codecs.VectorFormat;
 import org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat;
-import org.apache.lucene.codecs.lucene80.Lucene80NormsFormat;
 import org.apache.lucene.codecs.perfield.PerFieldDocValuesFormat;
 import org.apache.lucene.codecs.perfield.PerFieldPostingsFormat;
 
@@ -173,7 +173,7 @@ public class Lucene84Codec extends Codec {
   private final NormsFormat normsFormat = new Lucene80NormsFormat();
 
   @Override
-  public final NormsFormat normsFormat() {
+  public NormsFormat normsFormat() {
     return normsFormat;
   }
 }

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

@@ -22,6 +22,7 @@ import org.apache.lucene.backward_codecs.lucene50.Lucene50CompoundFormat;
 import org.apache.lucene.backward_codecs.lucene50.Lucene50LiveDocsFormat;
 import org.apache.lucene.backward_codecs.lucene50.Lucene50StoredFieldsFormat;
 import org.apache.lucene.backward_codecs.lucene60.Lucene60FieldInfosFormat;
+import org.apache.lucene.backward_codecs.lucene80.Lucene80NormsFormat;
 import org.apache.lucene.backward_codecs.lucene84.Lucene84PostingsFormat;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.CompoundFormat;
@@ -37,7 +38,6 @@ import org.apache.lucene.codecs.StoredFieldsFormat;
 import org.apache.lucene.codecs.TermVectorsFormat;
 import org.apache.lucene.codecs.VectorFormat;
 import org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat;
-import org.apache.lucene.codecs.lucene80.Lucene80NormsFormat;
 import org.apache.lucene.codecs.lucene86.Lucene86PointsFormat;
 import org.apache.lucene.codecs.lucene86.Lucene86SegmentInfoFormat;
 import org.apache.lucene.codecs.perfield.PerFieldDocValuesFormat;
@@ -49,8 +49,8 @@ import org.apache.lucene.codecs.perfield.PerFieldPostingsFormat;
  *
  * <p>If you want to reuse functionality of this codec in another codec, extend {@link FilterCodec}.
  *
- * @see org.apache.lucene.codecs.lucene86 package documentation for file format details.
  * @lucene.experimental
+ * @see org.apache.lucene.codecs.lucene86 package documentation for file format details.
  */
 public class Lucene86Codec extends Codec {
   private final TermVectorsFormat vectorsFormat = new Lucene50TermVectorsFormat();
@@ -175,7 +175,7 @@ public class Lucene86Codec extends Codec {
   private final NormsFormat normsFormat = new Lucene80NormsFormat();
 
   @Override
-  public final NormsFormat normsFormat() {
+  public NormsFormat normsFormat() {
     return normsFormat;
   }
 }

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

@@ -21,6 +21,8 @@ import java.util.Objects;
 import org.apache.lucene.backward_codecs.lucene50.Lucene50CompoundFormat;
 import org.apache.lucene.backward_codecs.lucene50.Lucene50LiveDocsFormat;
 import org.apache.lucene.backward_codecs.lucene60.Lucene60FieldInfosFormat;
+import org.apache.lucene.backward_codecs.lucene80.Lucene80DocValuesFormat;
+import org.apache.lucene.backward_codecs.lucene80.Lucene80NormsFormat;
 import org.apache.lucene.backward_codecs.lucene84.Lucene84PostingsFormat;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.CompoundFormat;
@@ -36,8 +38,6 @@ import org.apache.lucene.codecs.StoredFieldsFormat;
 import org.apache.lucene.codecs.TermVectorsFormat;
 import org.apache.lucene.codecs.VectorFormat;
 import org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat;
-import org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat;
-import org.apache.lucene.codecs.lucene80.Lucene80NormsFormat;
 import org.apache.lucene.codecs.lucene86.Lucene86PointsFormat;
 import org.apache.lucene.codecs.lucene86.Lucene86SegmentInfoFormat;
 import org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat;
@@ -187,7 +187,7 @@ public class Lucene87Codec extends Codec {
   private final NormsFormat normsFormat = new Lucene80NormsFormat();
 
   @Override
-  public final NormsFormat normsFormat() {
+  public NormsFormat normsFormat() {
     return normsFormat;
   }
 }

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

@@ -14,3 +14,4 @@
 #  limitations under the License.
 
 org.apache.lucene.backward_codecs.lucene70.Lucene70DocValuesFormat
+org.apache.lucene.backward_codecs.lucene80.Lucene80DocValuesFormat

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/Lucene87/Lucene87RWCodec.java

@@ -14,12 +14,13 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.backward_codecs.Lucene87;
+package org.apache.lucene.backward_codecs.lucene87;
 
 import org.apache.lucene.backward_codecs.lucene50.Lucene50RWCompoundFormat;
+import org.apache.lucene.backward_codecs.lucene80.Lucene80RWNormsFormat;
 import org.apache.lucene.backward_codecs.lucene84.Lucene84RWPostingsFormat;
-import org.apache.lucene.backward_codecs.lucene87.Lucene87Codec;
 import org.apache.lucene.codecs.CompoundFormat;
+import org.apache.lucene.codecs.NormsFormat;
 import org.apache.lucene.codecs.PostingsFormat;
 import org.apache.lucene.codecs.perfield.PerFieldPostingsFormat;
 
@@ -40,6 +41,11 @@ public class Lucene87RWCodec extends Lucene87Codec {
     return new Lucene50RWCompoundFormat();
   }
 
+  @Override
+  public NormsFormat normsFormat() {
+    return new Lucene80RWNormsFormat();
+  }
+
   @Override
   public PostingsFormat postingsFormat() {
     return postingsFormat;

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene50/TestLucene50CompoundFormat.java

@@ -16,7 +16,7 @@
  */
 package org.apache.lucene.backward_codecs.lucene50;
 
-import org.apache.lucene.backward_codecs.Lucene87.Lucene87RWCodec;
+import org.apache.lucene.backward_codecs.lucene87.Lucene87RWCodec;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.index.BaseCompoundFormatTestCase;
 

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene80/BaseLucene80DocValuesFormatTestCase.java

@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.backward_codecs.lucene80;
 
 import java.io.IOException;
 import java.util.ArrayList;

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene80/Lucene80NormsConsumer.java

@@ -14,9 +14,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.backward_codecs.lucene80;
 
-import static org.apache.lucene.codecs.lucene80.Lucene80NormsFormat.VERSION_CURRENT;
+import static org.apache.lucene.backward_codecs.lucene80.Lucene80NormsFormat.VERSION_CURRENT;
 
 import java.io.IOException;
 import org.apache.lucene.codecs.CodecUtil;

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene80/Lucene80RWNormsFormat.java

@@ -0,0 +1,30 @@
+/*
+ * 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.lucene80;
+
+import java.io.IOException;
+import org.apache.lucene.codecs.NormsConsumer;
+import org.apache.lucene.index.SegmentWriteState;
+
+public class Lucene80RWNormsFormat extends Lucene80NormsFormat {
+
+  @Override
+  public NormsConsumer normsConsumer(SegmentWriteState state) throws IOException {
+    return new Lucene80NormsConsumer(
+        state, DATA_CODEC, DATA_EXTENSION, METADATA_CODEC, METADATA_EXTENSION);
+  }
+}

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene80/TestBestCompressionLucene80DocValuesFormat.java

@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.backward_codecs.lucene80;
 
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.util.TestUtil;

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene80/TestBestSpeedLucene80DocValuesFormat.java

@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.backward_codecs.lucene80;
 
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.util.TestUtil;

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene80/TestDocValuesCompression.java

@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.backward_codecs.lucene80;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -25,7 +25,6 @@ import java.util.Set;
 import org.apache.lucene.analysis.Analyzer;
 import org.apache.lucene.analysis.standard.StandardAnalyzer;
 import org.apache.lucene.codecs.Codec;
-import org.apache.lucene.codecs.lucene90.Lucene90Codec;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.SortedDocValuesField;
@@ -43,8 +42,13 @@ import org.apache.lucene.util.LuceneTestCase;
 import org.apache.lucene.util.TestUtil;
 
 public class TestDocValuesCompression extends LuceneTestCase {
-  private final Codec bestSpeed = new Lucene90Codec(Lucene90Codec.Mode.BEST_SPEED);
+  private final Codec bestSpeed =
-  private final Codec bestCompression = new Lucene90Codec(Lucene90Codec.Mode.BEST_COMPRESSION);
+      TestUtil.alwaysDocValuesFormat(
+          new Lucene80DocValuesFormat(Lucene80DocValuesFormat.Mode.BEST_SPEED));
+
+  private final Codec bestCompression =
+      TestUtil.alwaysDocValuesFormat(
+          new Lucene80DocValuesFormat(Lucene80DocValuesFormat.Mode.BEST_COMPRESSION));
 
   public void testTermsDictCompressionForLowCardinalityFields() throws IOException {
     final int CARDINALITY = Lucene80DocValuesFormat.TERMS_DICT_BLOCK_COMPRESSION_THRESHOLD - 1;

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene80/TestIndexedDISI.java

@@ -0,0 +1,593 @@
+/*
+ * 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.lucene80;
+
+import java.io.IOException;
+import java.util.Random;
+import org.apache.lucene.search.DocIdSetIterator;
+import org.apache.lucene.store.Directory;
+import org.apache.lucene.store.IOContext;
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.store.IndexOutput;
+import org.apache.lucene.store.RandomAccessInput;
+import org.apache.lucene.util.BitSet;
+import org.apache.lucene.util.BitSetIterator;
+import org.apache.lucene.util.FixedBitSet;
+import org.apache.lucene.util.LuceneTestCase;
+import org.apache.lucene.util.SparseFixedBitSet;
+import org.apache.lucene.util.TestUtil;
+
+public class TestIndexedDISI extends LuceneTestCase {
+
+  public void testEmpty() throws IOException {
+    int maxDoc = TestUtil.nextInt(random(), 1, 100000);
+    BitSet set = new SparseFixedBitSet(maxDoc);
+    try (Directory dir = newDirectory()) {
+      doTest(set, dir);
+    }
+  }
+
+  // EMPTY blocks are special with regard to jumps as they have size 0
+  @Nightly
+  public void testEmptyBlocks() throws IOException {
+    final int B = 65536;
+    int maxDoc = B * 11;
+    BitSet set = new SparseFixedBitSet(maxDoc);
+    // block 0: EMPTY
+    set.set(B + 5); // block 1: SPARSE
+    // block 2: EMPTY
+    // block 3: EMPTY
+    set.set(B * 4 + 5); // block 4: SPARSE
+
+    for (int i = 0; i < B; i++) {
+      set.set(B * 6 + i); // block 6: ALL
+    }
+    for (int i = 0; i < B; i += 3) {
+      set.set(B * 7 + i); // block 7: DENSE
+    }
+    for (int i = 0; i < B; i++) {
+      if (i != 32768) {
+        set.set(B * 8 + i); // block 8: DENSE (all-1)
+      }
+    }
+    // block 9-11: EMPTY
+
+    try (Directory dir = newDirectory()) {
+      doTestAllSingleJump(set, dir);
+    }
+
+    // Change the first block to DENSE to see if jump-tables sets to position 0
+    set.set(0);
+    try (Directory dir = newDirectory()) {
+      doTestAllSingleJump(set, dir);
+    }
+  }
+
+  // EMPTY blocks are special with regard to jumps as they have size 0
+  public void testLastEmptyBlocks() throws IOException {
+    final int B = 65536;
+    int maxDoc = B * 3;
+    BitSet set = new SparseFixedBitSet(maxDoc);
+    for (int docID = 0; docID < B * 2; docID++) { // first 2 blocks are ALL
+      set.set(docID);
+    }
+    // Last block is EMPTY
+
+    try (Directory dir = newDirectory()) {
+      doTestAllSingleJump(set, dir);
+      assertAdvanceBeyondEnd(set, dir);
+    }
+  }
+
+  // Checks that advance after the end of the blocks has been reached has the correct behaviour
+  private void assertAdvanceBeyondEnd(BitSet set, Directory dir) throws IOException {
+    final int cardinality = set.cardinality();
+    final byte denseRankPower = 9; // Not tested here so fixed to isolate factors
+    long length;
+    int jumpTableentryCount;
+    try (IndexOutput out = dir.createOutput("bar", IOContext.DEFAULT)) {
+      jumpTableentryCount =
+          IndexedDISI.writeBitSet(new BitSetIterator(set, cardinality), out, denseRankPower);
+    }
+
+    try (IndexInput in = dir.openInput("bar", IOContext.DEFAULT)) {
+      BitSetIterator disi2 = new BitSetIterator(set, cardinality);
+      int doc = disi2.docID();
+      int index = 0;
+      while (doc < cardinality) {
+        doc = disi2.nextDoc();
+        index++;
+      }
+
+      IndexedDISI disi =
+          new IndexedDISI(in, 0L, in.length(), jumpTableentryCount, denseRankPower, cardinality);
+      // Advance 1 docID beyond end
+      assertFalse(
+          "There should be no set bit beyond the valid docID range",
+          disi.advanceExact(set.length()));
+      disi.advance(
+          doc); // Should be the special docID signifyin NO_MORE_DOCS from the BitSetIterator
+      assertEquals(
+          "The index when advancing beyond the last defined docID should be correct",
+          index,
+          disi.index() + 1); // disi.index()+1 as the while-loop also counts the NO_MORE_DOCS
+    }
+  }
+
+  // TODO: can this be toned down?
+  @Nightly
+  public void testRandomBlocks() throws IOException {
+    final int BLOCKS = 5;
+    BitSet set = createSetWithRandomBlocks(BLOCKS);
+    try (Directory dir = newDirectory()) {
+      doTestAllSingleJump(set, dir);
+    }
+  }
+
+  // When doing merges in Lucene80NormsProducer, IndexedDISI are created from slices where the
+  // offset is not 0
+  public void testPositionNotZero() throws IOException {
+    final int BLOCKS = 10;
+    final byte denseRankPower =
+        rarely() ? -1 : (byte) (random().nextInt(7) + 7); // sane + chance of disable
+
+    BitSet set = createSetWithRandomBlocks(BLOCKS);
+    try (Directory dir = newDirectory()) {
+      final int cardinality = set.cardinality();
+      int jumpTableEntryCount;
+      try (IndexOutput out = dir.createOutput("foo", IOContext.DEFAULT)) {
+        jumpTableEntryCount =
+            IndexedDISI.writeBitSet(new BitSetIterator(set, cardinality), out, denseRankPower);
+      }
+      try (IndexInput fullInput = dir.openInput("foo", IOContext.DEFAULT)) {
+        IndexInput blockData =
+            IndexedDISI.createBlockSlice(
+                fullInput, "blocks", 0, fullInput.length(), jumpTableEntryCount);
+        blockData.seek(random().nextInt((int) blockData.length()));
+
+        RandomAccessInput jumpTable =
+            IndexedDISI.createJumpTable(fullInput, 0, fullInput.length(), jumpTableEntryCount);
+        IndexedDISI disi =
+            new IndexedDISI(blockData, jumpTable, jumpTableEntryCount, denseRankPower, cardinality);
+        // This failed at some point during LUCENE-8585 development as it did not reset the slice
+        // position
+        disi.advanceExact(BLOCKS * 65536 - 1);
+      }
+    }
+  }
+
+  private BitSet createSetWithRandomBlocks(int blockCount) {
+    final int B = 65536;
+    BitSet set = new SparseFixedBitSet(blockCount * B);
+    for (int block = 0; block < blockCount; block++) {
+      switch (random().nextInt(4)) {
+        case 0:
+          { // EMPTY
+            break;
+          }
+        case 1:
+          { // ALL
+            for (int docID = block * B; docID < (block + 1) * B; docID++) {
+              set.set(docID);
+            }
+            break;
+          }
+        case 2:
+          { // SPARSE ( < 4096 )
+            for (int docID = block * B; docID < (block + 1) * B; docID += 101) {
+              set.set(docID);
+            }
+            break;
+          }
+        case 3:
+          { // DENSE ( >= 4096 )
+            for (int docID = block * B; docID < (block + 1) * B; docID += 3) {
+              set.set(docID);
+            }
+            break;
+          }
+        default:
+          throw new IllegalStateException(
+              "Modulo logic error: there should only be 4 possibilities");
+      }
+    }
+    return set;
+  }
+
+  private void doTestAllSingleJump(BitSet set, Directory dir) throws IOException {
+    final int cardinality = set.cardinality();
+    final byte denseRankPower =
+        rarely() ? -1 : (byte) (random().nextInt(7) + 7); // sane + chance of disable
+    long length;
+    int jumpTableentryCount;
+    try (IndexOutput out = dir.createOutput("foo", IOContext.DEFAULT)) {
+      jumpTableentryCount =
+          IndexedDISI.writeBitSet(new BitSetIterator(set, cardinality), out, denseRankPower);
+      length = out.getFilePointer();
+    }
+
+    try (IndexInput in = dir.openInput("foo", IOContext.DEFAULT)) {
+      for (int i = 0; i < set.length(); i++) {
+        IndexedDISI disi =
+            new IndexedDISI(in, 0L, length, jumpTableentryCount, denseRankPower, cardinality);
+        assertEquals(
+            "The bit at " + i + " should be correct with advanceExact",
+            set.get(i),
+            disi.advanceExact(i));
+
+        IndexedDISI disi2 =
+            new IndexedDISI(in, 0L, length, jumpTableentryCount, denseRankPower, cardinality);
+        disi2.advance(i);
+        // Proper sanity check with jump tables as an error could make them seek backwards
+        assertTrue(
+            "The docID should at least be "
+                + i
+                + " after advance("
+                + i
+                + ") but was "
+                + disi2.docID(),
+            i <= disi2.docID());
+        if (set.get(i)) {
+          assertEquals("The docID should be present with advance", i, disi2.docID());
+        } else {
+          assertNotSame("The docID should not be present with advance", i, disi2.docID());
+        }
+      }
+    }
+  }
+
+  public void testOneDoc() throws IOException {
+    int maxDoc = TestUtil.nextInt(random(), 1, 100000);
+    BitSet set = new SparseFixedBitSet(maxDoc);
+    set.set(random().nextInt(maxDoc));
+    try (Directory dir = newDirectory()) {
+      doTest(set, dir);
+    }
+  }
+
+  public void testTwoDocs() throws IOException {
+    int maxDoc = TestUtil.nextInt(random(), 1, 100000);
+    BitSet set = new SparseFixedBitSet(maxDoc);
+    set.set(random().nextInt(maxDoc));
+    set.set(random().nextInt(maxDoc));
+    try (Directory dir = newDirectory()) {
+      doTest(set, dir);
+    }
+  }
+
+  public void testAllDocs() throws IOException {
+    int maxDoc = TestUtil.nextInt(random(), 1, 100000);
+    FixedBitSet set = new FixedBitSet(maxDoc);
+    set.set(1, maxDoc);
+    try (Directory dir = newDirectory()) {
+      doTest(set, dir);
+    }
+  }
+
+  public void testHalfFull() throws IOException {
+    int maxDoc = TestUtil.nextInt(random(), 1, 100000);
+    BitSet set = new SparseFixedBitSet(maxDoc);
+    for (int i = random().nextInt(2); i < maxDoc; i += TestUtil.nextInt(random(), 1, 3)) {
+      set.set(i);
+    }
+    try (Directory dir = newDirectory()) {
+      doTest(set, dir);
+    }
+  }
+
+  public void testDocRange() throws IOException {
+    try (Directory dir = newDirectory()) {
+      for (int iter = 0; iter < 10; ++iter) {
+        int maxDoc = TestUtil.nextInt(random(), 1, 1000000);
+        FixedBitSet set = new FixedBitSet(maxDoc);
+        final int start = random().nextInt(maxDoc);
+        final int end = TestUtil.nextInt(random(), start + 1, maxDoc);
+        set.set(start, end);
+        doTest(set, dir);
+      }
+    }
+  }
+
+  public void testSparseDenseBoundary() throws IOException {
+    try (Directory dir = newDirectory()) {
+      FixedBitSet set = new FixedBitSet(200000);
+      int start = 65536 + random().nextInt(100);
+      final byte denseRankPower =
+          rarely() ? -1 : (byte) (random().nextInt(7) + 7); // sane + chance of disable
+
+      // we set MAX_ARRAY_LENGTH bits so the encoding will be sparse
+      set.set(start, start + IndexedDISI.MAX_ARRAY_LENGTH);
+      long length;
+      int jumpTableEntryCount;
+      try (IndexOutput out = dir.createOutput("sparse", IOContext.DEFAULT)) {
+        jumpTableEntryCount =
+            IndexedDISI.writeBitSet(
+                new BitSetIterator(set, IndexedDISI.MAX_ARRAY_LENGTH), out, denseRankPower);
+        length = out.getFilePointer();
+      }
+      try (IndexInput in = dir.openInput("sparse", IOContext.DEFAULT)) {
+        IndexedDISI disi =
+            new IndexedDISI(
+                in, 0L, length, jumpTableEntryCount, denseRankPower, IndexedDISI.MAX_ARRAY_LENGTH);
+        assertEquals(start, disi.nextDoc());
+        assertEquals(IndexedDISI.Method.SPARSE, disi.method);
+      }
+      doTest(set, dir);
+
+      // now we set one more bit so the encoding will be dense
+      set.set(start + IndexedDISI.MAX_ARRAY_LENGTH + random().nextInt(100));
+      try (IndexOutput out = dir.createOutput("bar", IOContext.DEFAULT)) {
+        IndexedDISI.writeBitSet(
+            new BitSetIterator(set, IndexedDISI.MAX_ARRAY_LENGTH + 1), out, denseRankPower);
+        length = out.getFilePointer();
+      }
+      try (IndexInput in = dir.openInput("bar", IOContext.DEFAULT)) {
+        IndexedDISI disi =
+            new IndexedDISI(
+                in,
+                0L,
+                length,
+                jumpTableEntryCount,
+                denseRankPower,
+                IndexedDISI.MAX_ARRAY_LENGTH + 1);
+        assertEquals(start, disi.nextDoc());
+        assertEquals(IndexedDISI.Method.DENSE, disi.method);
+      }
+      doTest(set, dir);
+    }
+  }
+
+  public void testOneDocMissing() throws IOException {
+    int maxDoc = TestUtil.nextInt(random(), 1, 1000000);
+    FixedBitSet set = new FixedBitSet(maxDoc);
+    set.set(0, maxDoc);
+    set.clear(random().nextInt(maxDoc));
+    try (Directory dir = newDirectory()) {
+      doTest(set, dir);
+    }
+  }
+
+  public void testFewMissingDocs() throws IOException {
+    try (Directory dir = newDirectory()) {
+      int numIters = atLeast(10);
+      for (int iter = 0; iter < numIters; ++iter) {
+        int maxDoc = TestUtil.nextInt(random(), 1, 100000);
+        FixedBitSet set = new FixedBitSet(maxDoc);
+        set.set(0, maxDoc);
+        final int numMissingDocs = TestUtil.nextInt(random(), 2, 1000);
+        for (int i = 0; i < numMissingDocs; ++i) {
+          set.clear(random().nextInt(maxDoc));
+        }
+        doTest(set, dir);
+      }
+    }
+  }
+
+  public void testDenseMultiBlock() throws IOException {
+    try (Directory dir = newDirectory()) {
+      int maxDoc = 10 * 65536; // 10 blocks
+      FixedBitSet set = new FixedBitSet(maxDoc);
+      for (int i = 0; i < maxDoc; i += 2) { // Set every other to ensure dense
+        set.set(i);
+      }
+      doTest(set, dir);
+    }
+  }
+
+  public void testIllegalDenseRankPower() throws IOException {
+
+    // Legal values
+    for (byte denseRankPower : new byte[] {-1, 7, 8, 9, 10, 11, 12, 13, 14, 15}) {
+      createAndOpenDISI(denseRankPower, denseRankPower);
+    }
+
+    // Illegal values
+    for (byte denseRankPower : new byte[] {-2, 0, 1, 6, 16}) {
+      try {
+        createAndOpenDISI(
+            denseRankPower, (byte) 8); // Illegal write, legal read (should not reach read)
+        fail(
+            "Trying to create an IndexedDISI data stream with denseRankPower-read "
+                + denseRankPower
+                + " and denseRankPower-write 8 should fail");
+      } catch (IllegalArgumentException e) {
+        // Expected
+      }
+      try {
+        createAndOpenDISI(
+            (byte) 8, denseRankPower); // Legal write, illegal read (should reach read)
+        fail(
+            "Trying to create an IndexedDISI data stream with denseRankPower-write 8 and denseRankPower-read "
+                + denseRankPower
+                + " should fail");
+      } catch (IllegalArgumentException e) {
+        // Expected
+      }
+    }
+  }
+
+  private void createAndOpenDISI(byte denseRankPowerWrite, byte denseRankPowerRead)
+      throws IOException {
+    BitSet set = new FixedBitSet(10);
+    set.set(set.length() - 1);
+    try (Directory dir = newDirectory()) {
+      long length;
+      int jumpTableEntryCount = -1;
+      try (IndexOutput out = dir.createOutput("foo", IOContext.DEFAULT)) {
+        jumpTableEntryCount =
+            IndexedDISI.writeBitSet(
+                new BitSetIterator(set, set.cardinality()), out, denseRankPowerWrite);
+        length = out.getFilePointer();
+      }
+      try (IndexInput in = dir.openInput("foo", IOContext.DEFAULT)) {
+        IndexedDISI disi =
+            new IndexedDISI(
+                in, 0L, length, jumpTableEntryCount, denseRankPowerRead, set.cardinality());
+      }
+      // This tests the legality of the denseRankPower only, so we don't do anything with the disi
+    }
+  }
+
+  public void testOneDocMissingFixed() throws IOException {
+    int maxDoc = 9699;
+    final byte denseRankPower =
+        rarely() ? -1 : (byte) (random().nextInt(7) + 7); // sane + chance of disable
+    FixedBitSet set = new FixedBitSet(maxDoc);
+    set.set(0, maxDoc);
+    set.clear(1345);
+    try (Directory dir = newDirectory()) {
+
+      final int cardinality = set.cardinality();
+      long length;
+      int jumpTableentryCount;
+      try (IndexOutput out = dir.createOutput("foo", IOContext.DEFAULT)) {
+        jumpTableentryCount =
+            IndexedDISI.writeBitSet(new BitSetIterator(set, cardinality), out, denseRankPower);
+        length = out.getFilePointer();
+      }
+
+      int step = 16000;
+      try (IndexInput in = dir.openInput("foo", IOContext.DEFAULT)) {
+        IndexedDISI disi =
+            new IndexedDISI(in, 0L, length, jumpTableentryCount, denseRankPower, cardinality);
+        BitSetIterator disi2 = new BitSetIterator(set, cardinality);
+        assertAdvanceEquality(disi, disi2, step);
+      }
+    }
+  }
+
+  public void testRandom() throws IOException {
+    try (Directory dir = newDirectory()) {
+      int numIters = atLeast(3);
+      for (int i = 0; i < numIters; ++i) {
+        doTestRandom(dir);
+      }
+    }
+  }
+
+  private void doTestRandom(Directory dir) throws IOException {
+    Random random = random();
+    final int maxStep = TestUtil.nextInt(random, 1, 1 << TestUtil.nextInt(random, 2, 20));
+    final int numDocs = TestUtil.nextInt(random, 1, Math.min(100000, Integer.MAX_VALUE / maxStep));
+    BitSet docs = new SparseFixedBitSet(numDocs * (maxStep + 1));
+    int lastDoc = -1;
+    for (int doc = -1, i = 0; i < numDocs; ++i) {
+      doc += TestUtil.nextInt(random, 1, maxStep);
+      docs.set(doc);
+      lastDoc = doc;
+    }
+    final int maxDoc = lastDoc + TestUtil.nextInt(random, 1, 100);
+
+    BitSet set = BitSet.of(new BitSetIterator(docs, docs.approximateCardinality()), maxDoc);
+    doTest(set, dir);
+  }
+
+  private void doTest(BitSet set, Directory dir) throws IOException {
+    final int cardinality = set.cardinality();
+    final byte denseRankPower =
+        rarely() ? -1 : (byte) (random().nextInt(7) + 7); // sane + chance of disable
+    long length;
+    int jumpTableentryCount;
+    try (IndexOutput out = dir.createOutput("foo", IOContext.DEFAULT)) {
+      jumpTableentryCount =
+          IndexedDISI.writeBitSet(new BitSetIterator(set, cardinality), out, denseRankPower);
+      length = out.getFilePointer();
+    }
+
+    try (IndexInput in = dir.openInput("foo", IOContext.DEFAULT)) {
+      IndexedDISI disi =
+          new IndexedDISI(in, 0L, length, jumpTableentryCount, denseRankPower, cardinality);
+      BitSetIterator disi2 = new BitSetIterator(set, cardinality);
+      assertSingleStepEquality(disi, disi2);
+    }
+
+    for (int step : new int[] {1, 10, 100, 1000, 10000, 100000}) {
+      try (IndexInput in = dir.openInput("foo", IOContext.DEFAULT)) {
+        IndexedDISI disi =
+            new IndexedDISI(in, 0L, length, jumpTableentryCount, denseRankPower, cardinality);
+        BitSetIterator disi2 = new BitSetIterator(set, cardinality);
+        assertAdvanceEquality(disi, disi2, step);
+      }
+    }
+
+    for (int step : new int[] {10, 100, 1000, 10000, 100000}) {
+      try (IndexInput in = dir.openInput("foo", IOContext.DEFAULT)) {
+        IndexedDISI disi =
+            new IndexedDISI(in, 0L, length, jumpTableentryCount, denseRankPower, cardinality);
+        BitSetIterator disi2 = new BitSetIterator(set, cardinality);
+        int disi2length = set.length();
+        assertAdvanceExactRandomized(disi, disi2, disi2length, step);
+      }
+    }
+
+    dir.deleteFile("foo");
+  }
+
+  private void assertAdvanceExactRandomized(
+      IndexedDISI disi, BitSetIterator disi2, int disi2length, int step) throws IOException {
+    int index = -1;
+    Random random = random();
+    for (int target = 0; target < disi2length; ) {
+      target += TestUtil.nextInt(random, 0, step);
+      int doc = disi2.docID();
+      while (doc < target) {
+        doc = disi2.nextDoc();
+        index++;
+      }
+
+      boolean exists = disi.advanceExact(target);
+      assertEquals(doc == target, exists);
+      if (exists) {
+        assertEquals(index, disi.index());
+      } else if (random.nextBoolean()) {
+        assertEquals(doc, disi.nextDoc());
+        // This is a bit strange when doc == NO_MORE_DOCS as the index overcounts in the disi2
+        // while-loop
+        assertEquals(index, disi.index());
+        target = doc;
+      }
+    }
+  }
+
+  private void assertSingleStepEquality(IndexedDISI disi, BitSetIterator disi2) throws IOException {
+    int i = 0;
+    for (int doc = disi2.nextDoc(); doc != DocIdSetIterator.NO_MORE_DOCS; doc = disi2.nextDoc()) {
+      assertEquals(doc, disi.nextDoc());
+      assertEquals(i++, disi.index());
+    }
+    assertEquals(DocIdSetIterator.NO_MORE_DOCS, disi.nextDoc());
+  }
+
+  private void assertAdvanceEquality(IndexedDISI disi, BitSetIterator disi2, int step)
+      throws IOException {
+    int index = -1;
+    while (true) {
+      int target = disi2.docID() + step;
+      int doc;
+      do {
+        doc = disi2.nextDoc();
+        index++;
+      } while (doc < target);
+      assertEquals(doc, disi.advance(target));
+      if (doc == DocIdSetIterator.NO_MORE_DOCS) {
+        break;
+      }
+      assertEquals(
+          "Expected equality using step " + step + " at docID " + doc, index, disi.index());
+    }
+  }
+}

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene80/TestLucene80NormsFormat.java

@@ -14,15 +14,15 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.backward_codecs.lucene80;
 
+import org.apache.lucene.backward_codecs.lucene87.Lucene87RWCodec;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.index.BaseNormsFormatTestCase;
-import org.apache.lucene.util.TestUtil;
 
 /** Tests Lucene80NormsFormat */
 public class TestLucene80NormsFormat extends BaseNormsFormatTestCase {
-  private final Codec codec = TestUtil.getDefaultCodec();
+  private final Codec codec = new Lucene87RWCodec();
 
   @Override
   protected Codec getCodec() {

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene80/TestLucene80NormsFormatMergeInstance.java

@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.backward_codecs.lucene80;
 
 /** Test the merge instance of the Lucene80 norms format. */
 public class TestLucene80NormsFormatMergeInstance extends TestLucene80NormsFormat {

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene84/Lucene84RWCodec.java

@@ -20,7 +20,9 @@ import org.apache.lucene.backward_codecs.lucene50.Lucene50RWCompoundFormat;
 import org.apache.lucene.backward_codecs.lucene50.Lucene50RWStoredFieldsFormat;
 import org.apache.lucene.backward_codecs.lucene60.Lucene60RWPointsFormat;
 import org.apache.lucene.backward_codecs.lucene70.Lucene70RWSegmentInfoFormat;
+import org.apache.lucene.backward_codecs.lucene80.Lucene80RWNormsFormat;
 import org.apache.lucene.codecs.CompoundFormat;
+import org.apache.lucene.codecs.NormsFormat;
 import org.apache.lucene.codecs.PointsFormat;
 import org.apache.lucene.codecs.PostingsFormat;
 import org.apache.lucene.codecs.SegmentInfoFormat;
@@ -54,6 +56,11 @@ public class Lucene84RWCodec extends Lucene84Codec {
     return new Lucene50RWStoredFieldsFormat();
   }
 
+  @Override
+  public NormsFormat normsFormat() {
+    return new Lucene80RWNormsFormat();
+  }
+
   @Override
   public PostingsFormat postingsFormat() {
     return postingsFormat;

lucene/backward-codecs/src/test/org/apache/lucene/backward_codecs/lucene86/Lucene86RWCodec.java

@@ -19,8 +19,10 @@ package org.apache.lucene.backward_codecs.lucene86;
 import org.apache.lucene.backward_codecs.lucene50.Lucene50RWCompoundFormat;
 import org.apache.lucene.backward_codecs.lucene50.Lucene50RWStoredFieldsFormat;
 import org.apache.lucene.backward_codecs.lucene50.Lucene50StoredFieldsFormat;
+import org.apache.lucene.backward_codecs.lucene80.Lucene80RWNormsFormat;
 import org.apache.lucene.backward_codecs.lucene84.Lucene84RWPostingsFormat;
 import org.apache.lucene.codecs.CompoundFormat;
+import org.apache.lucene.codecs.NormsFormat;
 import org.apache.lucene.codecs.PostingsFormat;
 import org.apache.lucene.codecs.StoredFieldsFormat;
 import org.apache.lucene.codecs.perfield.PerFieldPostingsFormat;
@@ -53,6 +55,11 @@ public class Lucene86RWCodec extends Lucene86Codec {
     return storedFieldsFormat;
   }
 
+  @Override
+  public NormsFormat normsFormat() {
+    return new Lucene80RWNormsFormat();
+  }
+
   @Override
   public PostingsFormat postingsFormat() {
     return postingsFormat;

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

@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.codecs.lucene90;
 
 import java.io.DataInput;
 import java.io.IOException;

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

@@ -31,8 +31,6 @@ import org.apache.lucene.codecs.StoredFieldsFormat;
 import org.apache.lucene.codecs.TermVectorsFormat;
 import org.apache.lucene.codecs.VectorFormat;
 import org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat;
-import org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat;
-import org.apache.lucene.codecs.lucene80.Lucene80NormsFormat;
 import org.apache.lucene.codecs.lucene86.Lucene86PointsFormat;
 import org.apache.lucene.codecs.lucene86.Lucene86SegmentInfoFormat;
 import org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat;
@@ -52,16 +50,16 @@ public class Lucene90Codec extends Codec {
   /** Configuration option for the codec. */
   public static enum Mode {
     /** Trade compression ratio for retrieval speed. */
-    BEST_SPEED(Lucene87StoredFieldsFormat.Mode.BEST_SPEED, Lucene80DocValuesFormat.Mode.BEST_SPEED),
+    BEST_SPEED(Lucene87StoredFieldsFormat.Mode.BEST_SPEED, Lucene90DocValuesFormat.Mode.BEST_SPEED),
     /** Trade retrieval speed for compression ratio. */
     BEST_COMPRESSION(
         Lucene87StoredFieldsFormat.Mode.BEST_COMPRESSION,
-        Lucene80DocValuesFormat.Mode.BEST_COMPRESSION);
+        Lucene90DocValuesFormat.Mode.BEST_COMPRESSION);
 
     private final Lucene87StoredFieldsFormat.Mode storedMode;
-    private final Lucene80DocValuesFormat.Mode dvMode;
+    private final Lucene90DocValuesFormat.Mode dvMode;
 
-    private Mode(Lucene87StoredFieldsFormat.Mode storedMode, Lucene80DocValuesFormat.Mode dvMode) {
+    private Mode(Lucene87StoredFieldsFormat.Mode storedMode, Lucene90DocValuesFormat.Mode dvMode) {
       this.storedMode = Objects.requireNonNull(storedMode);
       this.dvMode = Objects.requireNonNull(dvMode);
     }
@@ -109,7 +107,7 @@ public class Lucene90Codec extends Codec {
     this.storedFieldsFormat =
         new Lucene87StoredFieldsFormat(Objects.requireNonNull(mode).storedMode);
     this.defaultFormat = new Lucene90PostingsFormat();
-    this.defaultDVFormat = new Lucene80DocValuesFormat(mode.dvMode);
+    this.defaultDVFormat = new Lucene90DocValuesFormat(mode.dvMode);
   }
 
   @Override
@@ -189,7 +187,7 @@ public class Lucene90Codec extends Codec {
 
   private final DocValuesFormat defaultDVFormat;
 
-  private final NormsFormat normsFormat = new Lucene80NormsFormat();
+  private final NormsFormat normsFormat = new Lucene90NormsFormat();
 
   @Override
   public final NormsFormat normsFormat() {

lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90DocValuesFormat.java

@@ -0,0 +1,216 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.codecs.lucene90;
+
+import java.io.IOException;
+import java.util.Objects;
+import org.apache.lucene.codecs.DocValuesConsumer;
+import org.apache.lucene.codecs.DocValuesFormat;
+import org.apache.lucene.codecs.DocValuesProducer;
+import org.apache.lucene.index.DocValuesType;
+import org.apache.lucene.index.IndexWriterConfig;
+import org.apache.lucene.index.SegmentReadState;
+import org.apache.lucene.index.SegmentWriteState;
+import org.apache.lucene.store.DataOutput;
+import org.apache.lucene.util.SmallFloat;
+import org.apache.lucene.util.packed.DirectWriter;
+
+/**
+ * Lucene 9.0 DocValues format.
+ *
+ * <p>Documents that have a value for the field are encoded in a way that it is always possible to
+ * know the ordinal of the current document in the set of documents that have a value. For instance,
+ * say the set of documents that have a value for the field is <code>{1, 5, 6, 11}</code>. When the
+ * iterator is on <code>6</code>, it knows that this is the 3rd item of the set. This way, values
+ * can be stored densely and accessed based on their index at search time. If all documents in a
+ * segment have a value for the field, the index is the same as the doc ID, so this case is encoded
+ * implicitly and is very fast at query time. On the other hand if some documents are missing a
+ * value for the field then the set of documents that have a value is encoded into blocks. All doc
+ * IDs that share the same upper 16 bits are encoded into the same block with the following
+ * strategies:
+ *
+ * <ul>
+ *   <li>SPARSE: This strategy is used when a block contains at most 4095 documents. The lower 16
+ *       bits of doc IDs are stored as {@link DataOutput#writeShort(short) shorts} while the upper
+ *       16 bits are given by the block ID.
+ *   <li>DENSE: This strategy is used when a block contains between 4096 and 65535 documents. The
+ *       lower bits of doc IDs are stored in a bit set. Advancing &lt; 512 documents is performed
+ *       using {@link Long#numberOfTrailingZeros(long) ntz} operations while the index is computed
+ *       by accumulating the {@link Long#bitCount(long) bit counts} of the visited longs. Advancing
+ *       &gt;= 512 documents is performed by skipping to the start of the needed 512 document
+ *       sub-block and iterating to the specific document within that block. The index for the
+ *       sub-block that is skipped to is retrieved from a rank-table positioned beforethe bit set.
+ *       The rank-table holds the origo index numbers for all 512 documents sub-blocks, represented
+ *       as an unsigned short for each 128 blocks.
+ *   <li>ALL: This strategy is used when a block contains exactly 65536 documents, meaning that the
+ *       block is full. In that case doc IDs do not need to be stored explicitly. This is typically
+ *       faster than both SPARSE and DENSE which is a reason why it is preferable to have all
+ *       documents that have a value for a field using contiguous doc IDs, for instance by using
+ *       {@link IndexWriterConfig#setIndexSort(org.apache.lucene.search.Sort) index sorting}.
+ * </ul>
+ *
+ * <p>Skipping blocks to arrive at a wanted document is either done on an iterative basis or by
+ * using the jump-table stored at the end of the chain of blocks. The jump-table holds the offset as
+ * well as the index for all blocks, packed in a single long per block.
+ *
+ * <p>Then the five per-document value types (Numeric,Binary,Sorted,SortedSet,SortedNumeric) are
+ * encoded using the following strategies:
+ *
+ * <p>{@link DocValuesType#NUMERIC NUMERIC}:
+ *
+ * <ul>
+ *   <li>Delta-compressed: per-document integers written as deltas from the minimum value,
+ *       compressed with bitpacking. For more information, see {@link DirectWriter}.
+ *   <li>Table-compressed: when the number of unique values is very small (&lt; 256), and when there
+ *       are unused "gaps" in the range of values used (such as {@link SmallFloat}), a lookup table
+ *       is written instead. Each per-document entry is instead the ordinal to this table, and those
+ *       ordinals are compressed with bitpacking ({@link DirectWriter}).
+ *   <li>GCD-compressed: when all numbers share a common divisor, such as dates, the greatest common
+ *       denominator (GCD) is computed, and quotients are stored using Delta-compressed Numerics.
+ *   <li>Monotonic-compressed: when all numbers are monotonically increasing offsets, they are
+ *       written as blocks of bitpacked integers, encoding the deviation from the expected delta.
+ *   <li>Const-compressed: when there is only one possible value, no per-document data is needed and
+ *       this value is encoded alone.
+ * </ul>
+ *
+ * <p>Depending on calculated gains, the numbers might be split into blocks of 16384 values. In that
+ * case, a jump-table with block offsets is appended to the blocks for O(1) access to the needed
+ * block.
+ *
+ * <p>{@link DocValuesType#BINARY BINARY}:
+ *
+ * <ul>
+ *   <li>Fixed-width Binary: one large concatenated byte[] is written, along with the fixed length.
+ *       Each document's value can be addressed directly with multiplication ({@code docID *
+ *       length}).
+ *   <li>Variable-width Binary: one large concatenated byte[] is written, along with end addresses
+ *       for each document. The addresses are written as Monotonic-compressed numerics.
+ *   <li>Prefix-compressed Binary: values are written in chunks of 16, with the first value written
+ *       completely and other values sharing prefixes. chunk addresses are written as
+ *       Monotonic-compressed numerics. A reverse lookup index is written from a portion of every
+ *       1024th term.
+ * </ul>
+ *
+ * <p>{@link DocValuesType#SORTED SORTED}:
+ *
+ * <ul>
+ *   <li>Sorted: a mapping of ordinals to deduplicated terms is written as Prefix-compressed Binary,
+ *       along with the per-document ordinals written using one of the numeric strategies above.
+ * </ul>
+ *
+ * <p>{@link DocValuesType#SORTED_SET SORTED_SET}:
+ *
+ * <ul>
+ *   <li>Single: if all documents have 0 or 1 value, then data are written like SORTED.
+ *   <li>SortedSet: a mapping of ordinals to deduplicated terms is written as Binary, an ordinal
+ *       list and per-document index into this list are written using the numeric strategies above.
+ * </ul>
+ *
+ * <p>{@link DocValuesType#SORTED_NUMERIC SORTED_NUMERIC}:
+ *
+ * <ul>
+ *   <li>Single: if all documents have 0 or 1 value, then data are written like NUMERIC.
+ *   <li>SortedNumeric: a value list and per-document index into this list are written using the
+ *       numeric strategies above.
+ * </ul>
+ *
+ * <p>Files:
+ *
+ * <ol>
+ *   <li><code>.dvd</code>: DocValues data
+ *   <li><code>.dvm</code>: DocValues metadata
+ * </ol>
+ *
+ * @lucene.experimental
+ */
+public final class Lucene90DocValuesFormat extends DocValuesFormat {
+
+  /** Configuration option for doc values. */
+  public static enum Mode {
+    /** Trade compression ratio for retrieval speed. */
+    BEST_SPEED,
+    /** Trade retrieval speed for compression ratio. */
+    BEST_COMPRESSION
+  }
+
+  /** Attribute key for compression mode. */
+  public static final String MODE_KEY = Lucene90DocValuesFormat.class.getSimpleName() + ".mode";
+
+  private final Mode mode;
+
+  /** Default constructor. */
+  public Lucene90DocValuesFormat() {
+    this(Mode.BEST_SPEED);
+  }
+
+  /** Constructor */
+  public Lucene90DocValuesFormat(Mode mode) {
+    super("Lucene90");
+    this.mode = Objects.requireNonNull(mode);
+  }
+
+  @Override
+  public DocValuesConsumer fieldsConsumer(SegmentWriteState state) throws IOException {
+    return new Lucene90DocValuesConsumer(
+        state, DATA_CODEC, DATA_EXTENSION, META_CODEC, META_EXTENSION, mode);
+  }
+
+  @Override
+  public DocValuesProducer fieldsProducer(SegmentReadState state) throws IOException {
+    return new Lucene90DocValuesProducer(
+        state, DATA_CODEC, DATA_EXTENSION, META_CODEC, META_EXTENSION);
+  }
+
+  static final String DATA_CODEC = "Lucene90DocValuesData";
+  static final String DATA_EXTENSION = "dvd";
+  static final String META_CODEC = "Lucene90DocValuesMetadata";
+  static final String META_EXTENSION = "dvm";
+  static final int VERSION_START = 0;
+  static final int VERSION_CURRENT = VERSION_START;
+
+  // indicates docvalues type
+  static final byte NUMERIC = 0;
+  static final byte BINARY = 1;
+  static final byte SORTED = 2;
+  static final byte SORTED_SET = 3;
+  static final byte SORTED_NUMERIC = 4;
+
+  static final int DIRECT_MONOTONIC_BLOCK_SHIFT = 16;
+
+  static final int NUMERIC_BLOCK_SHIFT = 14;
+  static final int NUMERIC_BLOCK_SIZE = 1 << NUMERIC_BLOCK_SHIFT;
+
+  static final int BINARY_BLOCK_SHIFT = 5;
+  static final int BINARY_DOCS_PER_COMPRESSED_BLOCK = 1 << BINARY_BLOCK_SHIFT;
+
+  static final int TERMS_DICT_BLOCK_SHIFT = 4;
+  static final int TERMS_DICT_BLOCK_SIZE = 1 << TERMS_DICT_BLOCK_SHIFT;
+  static final int TERMS_DICT_BLOCK_MASK = TERMS_DICT_BLOCK_SIZE - 1;
+
+  static final int TERMS_DICT_BLOCK_COMPRESSION_THRESHOLD = 32;
+  static final int TERMS_DICT_BLOCK_LZ4_SHIFT = 6;
+  static final int TERMS_DICT_BLOCK_LZ4_SIZE = 1 << TERMS_DICT_BLOCK_LZ4_SHIFT;
+  static final int TERMS_DICT_BLOCK_LZ4_MASK = TERMS_DICT_BLOCK_LZ4_SIZE - 1;
+  static final int TERMS_DICT_COMPRESSOR_LZ4_CODE = 1;
+  // Writing a special code so we know this is a LZ4-compressed block.
+  static final int TERMS_DICT_BLOCK_LZ4_CODE =
+      TERMS_DICT_BLOCK_LZ4_SHIFT << 16 | TERMS_DICT_COMPRESSOR_LZ4_CODE;
+
+  static final int TERMS_DICT_REVERSE_INDEX_SHIFT = 10;
+  static final int TERMS_DICT_REVERSE_INDEX_SIZE = 1 << TERMS_DICT_REVERSE_INDEX_SHIFT;
+  static final int TERMS_DICT_REVERSE_INDEX_MASK = TERMS_DICT_REVERSE_INDEX_SIZE - 1;
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90NormsConsumer.java

@@ -0,0 +1,176 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.codecs.lucene90;
+
+import static org.apache.lucene.codecs.lucene90.Lucene90NormsFormat.VERSION_CURRENT;
+
+import java.io.IOException;
+import org.apache.lucene.codecs.CodecUtil;
+import org.apache.lucene.codecs.NormsConsumer;
+import org.apache.lucene.codecs.NormsProducer;
+import org.apache.lucene.index.FieldInfo;
+import org.apache.lucene.index.IndexFileNames;
+import org.apache.lucene.index.NumericDocValues;
+import org.apache.lucene.index.SegmentWriteState;
+import org.apache.lucene.search.DocIdSetIterator;
+import org.apache.lucene.store.IndexOutput;
+import org.apache.lucene.util.IOUtils;
+
+/** Writer for {@link Lucene90NormsFormat} */
+final class Lucene90NormsConsumer extends NormsConsumer {
+  IndexOutput data, meta;
+  final int maxDoc;
+
+  Lucene90NormsConsumer(
+      SegmentWriteState state,
+      String dataCodec,
+      String dataExtension,
+      String metaCodec,
+      String metaExtension)
+      throws IOException {
+    boolean success = false;
+    try {
+      String dataName =
+          IndexFileNames.segmentFileName(
+              state.segmentInfo.name, state.segmentSuffix, dataExtension);
+      data = state.directory.createOutput(dataName, state.context);
+      CodecUtil.writeIndexHeader(
+          data, dataCodec, VERSION_CURRENT, state.segmentInfo.getId(), state.segmentSuffix);
+      String metaName =
+          IndexFileNames.segmentFileName(
+              state.segmentInfo.name, state.segmentSuffix, metaExtension);
+      meta = state.directory.createOutput(metaName, state.context);
+      CodecUtil.writeIndexHeader(
+          meta, metaCodec, VERSION_CURRENT, state.segmentInfo.getId(), state.segmentSuffix);
+      maxDoc = state.segmentInfo.maxDoc();
+      success = true;
+    } finally {
+      if (!success) {
+        IOUtils.closeWhileHandlingException(this);
+      }
+    }
+  }
+
+  @Override
+  public void close() throws IOException {
+    boolean success = false;
+    try {
+      if (meta != null) {
+        meta.writeInt(-1); // write EOF marker
+        CodecUtil.writeFooter(meta); // write checksum
+      }
+      if (data != null) {
+        CodecUtil.writeFooter(data); // write checksum
+      }
+      success = true;
+    } finally {
+      if (success) {
+        IOUtils.close(data, meta);
+      } else {
+        IOUtils.closeWhileHandlingException(data, meta);
+      }
+      meta = data = null;
+    }
+  }
+
+  @Override
+  public void addNormsField(FieldInfo field, NormsProducer normsProducer) throws IOException {
+    NumericDocValues values = normsProducer.getNorms(field);
+    int numDocsWithValue = 0;
+    long min = Long.MAX_VALUE;
+    long max = Long.MIN_VALUE;
+    for (int doc = values.nextDoc(); doc != DocIdSetIterator.NO_MORE_DOCS; doc = values.nextDoc()) {
+      numDocsWithValue++;
+      long v = values.longValue();
+      min = Math.min(min, v);
+      max = Math.max(max, v);
+    }
+    assert numDocsWithValue <= maxDoc;
+
+    meta.writeInt(field.number);
+
+    if (numDocsWithValue == 0) {
+      meta.writeLong(-2); // docsWithFieldOffset
+      meta.writeLong(0L); // docsWithFieldLength
+      meta.writeShort((short) -1); // jumpTableEntryCount
+      meta.writeByte((byte) -1); // denseRankPower
+    } else if (numDocsWithValue == maxDoc) {
+      meta.writeLong(-1); // docsWithFieldOffset
+      meta.writeLong(0L); // docsWithFieldLength
+      meta.writeShort((short) -1); // jumpTableEntryCount
+      meta.writeByte((byte) -1); // denseRankPower
+    } else {
+      long offset = data.getFilePointer();
+      meta.writeLong(offset); // docsWithFieldOffset
+      values = normsProducer.getNorms(field);
+      final short jumpTableEntryCount =
+          IndexedDISI.writeBitSet(values, data, IndexedDISI.DEFAULT_DENSE_RANK_POWER);
+      meta.writeLong(data.getFilePointer() - offset); // docsWithFieldLength
+      meta.writeShort(jumpTableEntryCount);
+      meta.writeByte(IndexedDISI.DEFAULT_DENSE_RANK_POWER);
+    }
+
+    meta.writeInt(numDocsWithValue);
+    int numBytesPerValue = numBytesPerValue(min, max);
+
+    meta.writeByte((byte) numBytesPerValue);
+    if (numBytesPerValue == 0) {
+      meta.writeLong(min);
+    } else {
+      meta.writeLong(data.getFilePointer()); // normsOffset
+      values = normsProducer.getNorms(field);
+      writeValues(values, numBytesPerValue, data);
+    }
+  }
+
+  private int numBytesPerValue(long min, long max) {
+    if (min >= max) {
+      return 0;
+    } else if (min >= Byte.MIN_VALUE && max <= Byte.MAX_VALUE) {
+      return 1;
+    } else if (min >= Short.MIN_VALUE && max <= Short.MAX_VALUE) {
+      return 2;
+    } else if (min >= Integer.MIN_VALUE && max <= Integer.MAX_VALUE) {
+      return 4;
+    } else {
+      return 8;
+    }
+  }
+
+  private void writeValues(NumericDocValues values, int numBytesPerValue, IndexOutput out)
+      throws IOException, AssertionError {
+    for (int doc = values.nextDoc(); doc != DocIdSetIterator.NO_MORE_DOCS; doc = values.nextDoc()) {
+      long value = values.longValue();
+      switch (numBytesPerValue) {
+        case 1:
+          out.writeByte((byte) value);
+          break;
+        case 2:
+          out.writeShort((short) value);
+          break;
+        case 4:
+          out.writeInt((int) value);
+          break;
+        case 8:
+          out.writeLong(value);
+          break;
+        default:
+          throw new AssertionError();
+      }
+    }
+  }
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90NormsFormat.java

@@ -0,0 +1,106 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.codecs.lucene90;
+
+import java.io.IOException;
+import org.apache.lucene.codecs.CodecUtil;
+import org.apache.lucene.codecs.NormsConsumer;
+import org.apache.lucene.codecs.NormsFormat;
+import org.apache.lucene.codecs.NormsProducer;
+import org.apache.lucene.index.SegmentReadState;
+import org.apache.lucene.index.SegmentWriteState;
+import org.apache.lucene.store.DataOutput;
+
+/**
+ * Lucene 9.0 Score normalization format.
+ *
+ * <p>Encodes normalization values by encoding each value with the minimum number of bytes needed to
+ * represent the range (which can be zero).
+ *
+ * <p>Files:
+ *
+ * <ol>
+ *   <li><code>.nvd</code>: Norms data
+ *   <li><code>.nvm</code>: Norms metadata
+ * </ol>
+ *
+ * <ol>
+ *   <li><a id="nvm"></a>
+ *       <p>The Norms metadata or .nvm file.
+ *       <p>For each norms field, this stores metadata, such as the offset into the Norms data
+ *       (.nvd)
+ *       <p>Norms metadata (.dvm) --&gt; Header,&lt;Entry&gt;<sup>NumFields</sup>,Footer
+ *       <ul>
+ *         <li>Header --&gt; {@link CodecUtil#writeIndexHeader IndexHeader}
+ *         <li>Entry --&gt; FieldNumber, DocsWithFieldAddress, DocsWithFieldLength,
+ *             NumDocsWithField, BytesPerNorm, NormsAddress
+ *         <li>FieldNumber --&gt; {@link DataOutput#writeInt Int32}
+ *         <li>DocsWithFieldAddress --&gt; {@link DataOutput#writeLong Int64}
+ *         <li>DocsWithFieldLength --&gt; {@link DataOutput#writeLong Int64}
+ *         <li>NumDocsWithField --&gt; {@link DataOutput#writeInt Int32}
+ *         <li>BytesPerNorm --&gt; {@link DataOutput#writeByte byte}
+ *         <li>NormsAddress --&gt; {@link DataOutput#writeLong Int64}
+ *         <li>Footer --&gt; {@link CodecUtil#writeFooter CodecFooter}
+ *       </ul>
+ *       <p>FieldNumber of -1 indicates the end of metadata.
+ *       <p>NormsAddress is the pointer to the start of the data in the norms data (.nvd), or the
+ *       singleton value when BytesPerValue = 0. If BytesPerValue is different from 0 then there are
+ *       NumDocsWithField values to read at that offset.
+ *       <p>DocsWithFieldAddress is the pointer to the start of the bit set containing documents
+ *       that have a norm in the norms data (.nvd), or -2 if no documents have a norm value, or -1
+ *       if all documents have a norm value.
+ *       <p>DocsWithFieldLength is the number of bytes used to encode the set of documents that have
+ *       a norm.
+ *   <li><a id="nvd"></a>
+ *       <p>The Norms data or .nvd file.
+ *       <p>For each Norms field, this stores the actual per-document data (the heavy-lifting)
+ *       <p>Norms data (.nvd) --&gt; Header,&lt; Data &gt;<sup>NumFields</sup>,Footer
+ *       <ul>
+ *         <li>Header --&gt; {@link CodecUtil#writeIndexHeader IndexHeader}
+ *         <li>DocsWithFieldData --&gt; {@link IndexedDISI#writeBitSet Bit set of MaxDoc bits}
+ *         <li>NormsData --&gt; {@link DataOutput#writeByte(byte) byte}<sup>NumDocsWithField *
+ *             BytesPerValue</sup>
+ *         <li>Footer --&gt; {@link CodecUtil#writeFooter CodecFooter}
+ *       </ul>
+ * </ol>
+ *
+ * @lucene.experimental
+ */
+public class Lucene90NormsFormat extends NormsFormat {
+
+  /** Sole Constructor */
+  public Lucene90NormsFormat() {}
+
+  @Override
+  public NormsConsumer normsConsumer(SegmentWriteState state) throws IOException {
+    return new Lucene90NormsConsumer(
+        state, DATA_CODEC, DATA_EXTENSION, METADATA_CODEC, METADATA_EXTENSION);
+  }
+
+  @Override
+  public NormsProducer normsProducer(SegmentReadState state) throws IOException {
+    return new Lucene90NormsProducer(
+        state, DATA_CODEC, DATA_EXTENSION, METADATA_CODEC, METADATA_EXTENSION);
+  }
+
+  private static final String DATA_CODEC = "Lucene90NormsData";
+  private static final String DATA_EXTENSION = "nvd";
+  private static final String METADATA_CODEC = "Lucene90NormsMetadata";
+  private static final String METADATA_EXTENSION = "nvm";
+  static final int VERSION_START = 0;
+  static final int VERSION_CURRENT = VERSION_START;
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90NormsProducer.java

@@ -0,0 +1,492 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.codecs.lucene90;
+
+import static org.apache.lucene.codecs.lucene90.Lucene90NormsFormat.VERSION_CURRENT;
+import static org.apache.lucene.codecs.lucene90.Lucene90NormsFormat.VERSION_START;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+import org.apache.lucene.codecs.CodecUtil;
+import org.apache.lucene.codecs.NormsProducer;
+import org.apache.lucene.index.CorruptIndexException;
+import org.apache.lucene.index.DocValues;
+import org.apache.lucene.index.FieldInfo;
+import org.apache.lucene.index.FieldInfos;
+import org.apache.lucene.index.IndexFileNames;
+import org.apache.lucene.index.NumericDocValues;
+import org.apache.lucene.index.SegmentReadState;
+import org.apache.lucene.store.ChecksumIndexInput;
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.store.RandomAccessInput;
+import org.apache.lucene.util.IOUtils;
+
+/** Reader for {@link Lucene90NormsFormat} */
+final class Lucene90NormsProducer extends NormsProducer implements Cloneable {
+  // metadata maps (just file pointers and minimal stuff)
+  private final Map<Integer, NormsEntry> norms = new HashMap<>();
+  private final int maxDoc;
+  private IndexInput data;
+  private boolean merging;
+  private Map<Integer, IndexInput> disiInputs;
+  private Map<Integer, RandomAccessInput> disiJumpTables;
+  private Map<Integer, RandomAccessInput> dataInputs;
+
+  Lucene90NormsProducer(
+      SegmentReadState state,
+      String dataCodec,
+      String dataExtension,
+      String metaCodec,
+      String metaExtension)
+      throws IOException {
+    maxDoc = state.segmentInfo.maxDoc();
+    String metaName =
+        IndexFileNames.segmentFileName(state.segmentInfo.name, state.segmentSuffix, metaExtension);
+    int version = -1;
+
+    // read in the entries from the metadata file.
+    try (ChecksumIndexInput in = state.directory.openChecksumInput(metaName, state.context)) {
+      Throwable priorE = null;
+      try {
+        version =
+            CodecUtil.checkIndexHeader(
+                in,
+                metaCodec,
+                VERSION_START,
+                VERSION_CURRENT,
+                state.segmentInfo.getId(),
+                state.segmentSuffix);
+        readFields(in, state.fieldInfos);
+      } catch (Throwable exception) {
+        priorE = exception;
+      } finally {
+        CodecUtil.checkFooter(in, priorE);
+      }
+    }
+
+    String dataName =
+        IndexFileNames.segmentFileName(state.segmentInfo.name, state.segmentSuffix, dataExtension);
+    data = state.directory.openInput(dataName, state.context);
+    boolean success = false;
+    try {
+      final int version2 =
+          CodecUtil.checkIndexHeader(
+              data,
+              dataCodec,
+              VERSION_START,
+              VERSION_CURRENT,
+              state.segmentInfo.getId(),
+              state.segmentSuffix);
+      if (version != version2) {
+        throw new CorruptIndexException(
+            "Format versions mismatch: meta=" + version + ",data=" + version2, data);
+      }
+
+      // NOTE: data file is too costly to verify checksum against all the bytes on open,
+      // but for now we at least verify proper structure of the checksum footer: which looks
+      // for FOOTER_MAGIC + algorithmID. This is cheap and can detect some forms of corruption
+      // such as file truncation.
+      CodecUtil.retrieveChecksum(data);
+
+      success = true;
+    } finally {
+      if (!success) {
+        IOUtils.closeWhileHandlingException(this.data);
+      }
+    }
+  }
+
+  @Override
+  public NormsProducer getMergeInstance() {
+    Lucene90NormsProducer clone;
+    try {
+      clone = (Lucene90NormsProducer) super.clone();
+    } catch (CloneNotSupportedException e) {
+      // cannot happen
+      throw new RuntimeException(e);
+    }
+    clone.data = data.clone();
+    clone.disiInputs = new HashMap<>();
+    clone.disiJumpTables = new HashMap<>();
+    clone.dataInputs = new HashMap<>();
+    clone.merging = true;
+    return clone;
+  }
+
+  static class NormsEntry {
+    byte denseRankPower;
+    byte bytesPerNorm;
+    long docsWithFieldOffset;
+    long docsWithFieldLength;
+    short jumpTableEntryCount;
+    int numDocsWithField;
+    long normsOffset;
+  }
+
+  abstract static class DenseNormsIterator extends NumericDocValues {
+
+    final int maxDoc;
+    int doc = -1;
+
+    DenseNormsIterator(int maxDoc) {
+      this.maxDoc = maxDoc;
+    }
+
+    @Override
+    public int docID() {
+      return doc;
+    }
+
+    @Override
+    public int nextDoc() throws IOException {
+      return advance(doc + 1);
+    }
+
+    @Override
+    public int advance(int target) throws IOException {
+      if (target >= maxDoc) {
+        return doc = NO_MORE_DOCS;
+      }
+      return doc = target;
+    }
+
+    @Override
+    public boolean advanceExact(int target) throws IOException {
+      this.doc = target;
+      return true;
+    }
+
+    @Override
+    public long cost() {
+      return maxDoc;
+    }
+  }
+
+  abstract static class SparseNormsIterator extends NumericDocValues {
+
+    final IndexedDISI disi;
+
+    SparseNormsIterator(IndexedDISI disi) {
+      this.disi = disi;
+    }
+
+    @Override
+    public int docID() {
+      return disi.docID();
+    }
+
+    @Override
+    public int nextDoc() throws IOException {
+      return disi.nextDoc();
+    }
+
+    @Override
+    public int advance(int target) throws IOException {
+      return disi.advance(target);
+    }
+
+    @Override
+    public boolean advanceExact(int target) throws IOException {
+      return disi.advanceExact(target);
+    }
+
+    @Override
+    public long cost() {
+      return disi.cost();
+    }
+  }
+
+  private void readFields(IndexInput 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);
+      } else if (!info.hasNorms()) {
+        throw new CorruptIndexException("Invalid field: " + info.name, meta);
+      }
+      NormsEntry entry = new NormsEntry();
+      entry.docsWithFieldOffset = meta.readLong();
+      entry.docsWithFieldLength = meta.readLong();
+      entry.jumpTableEntryCount = meta.readShort();
+      entry.denseRankPower = meta.readByte();
+      entry.numDocsWithField = meta.readInt();
+      entry.bytesPerNorm = meta.readByte();
+      switch (entry.bytesPerNorm) {
+        case 0:
+        case 1:
+        case 2:
+        case 4:
+        case 8:
+          break;
+        default:
+          throw new CorruptIndexException(
+              "Invalid bytesPerValue: " + entry.bytesPerNorm + ", field: " + info.name, meta);
+      }
+      entry.normsOffset = meta.readLong();
+      norms.put(info.number, entry);
+    }
+  }
+
+  private RandomAccessInput getDataInput(FieldInfo field, NormsEntry entry) throws IOException {
+    RandomAccessInput slice = null;
+    if (merging) {
+      slice = dataInputs.get(field.number);
+    }
+    if (slice == null) {
+      slice =
+          data.randomAccessSlice(
+              entry.normsOffset, entry.numDocsWithField * (long) entry.bytesPerNorm);
+      if (merging) {
+        dataInputs.put(field.number, slice);
+      }
+    }
+    return slice;
+  }
+
+  private IndexInput getDisiInput(FieldInfo field, NormsEntry entry) throws IOException {
+    if (merging == false) {
+      return IndexedDISI.createBlockSlice(
+          data,
+          "docs",
+          entry.docsWithFieldOffset,
+          entry.docsWithFieldLength,
+          entry.jumpTableEntryCount);
+    }
+
+    IndexInput in = disiInputs.get(field.number);
+    if (in == null) {
+      in =
+          IndexedDISI.createBlockSlice(
+              data,
+              "docs",
+              entry.docsWithFieldOffset,
+              entry.docsWithFieldLength,
+              entry.jumpTableEntryCount);
+      disiInputs.put(field.number, in);
+    }
+
+    final IndexInput inF = in; // same as in but final
+
+    // Wrap so that reads can be interleaved from the same thread if two
+    // norms instances are pulled and consumed in parallel. Merging usually
+    // doesn't need this feature but CheckIndex might, plus we need merge
+    // instances to behave well and not be trappy.
+    return new IndexInput("docs") {
+
+      long offset = 0;
+
+      @Override
+      public void readBytes(byte[] b, int off, int len) throws IOException {
+        inF.seek(offset);
+        offset += len;
+        inF.readBytes(b, off, len);
+      }
+
+      @Override
+      public byte readByte() throws IOException {
+        throw new UnsupportedOperationException("Unused by IndexedDISI");
+      }
+
+      @Override
+      public IndexInput slice(String sliceDescription, long offset, long length)
+          throws IOException {
+        throw new UnsupportedOperationException("Unused by IndexedDISI");
+      }
+
+      @Override
+      public short readShort() throws IOException {
+        inF.seek(offset);
+        offset += Short.BYTES;
+        return inF.readShort();
+      }
+
+      @Override
+      public long readLong() throws IOException {
+        inF.seek(offset);
+        offset += Long.BYTES;
+        return inF.readLong();
+      }
+
+      @Override
+      public void seek(long pos) throws IOException {
+        offset = pos;
+      }
+
+      @Override
+      public long length() {
+        throw new UnsupportedOperationException("Unused by IndexedDISI");
+      }
+
+      @Override
+      public long getFilePointer() {
+        return offset;
+      }
+
+      @Override
+      public void close() throws IOException {
+        throw new UnsupportedOperationException("Unused by IndexedDISI");
+      }
+    };
+  }
+
+  private RandomAccessInput getDisiJumpTable(FieldInfo field, NormsEntry entry) throws IOException {
+    RandomAccessInput jumpTable = null;
+    if (merging) {
+      jumpTable = disiJumpTables.get(field.number);
+    }
+    if (jumpTable == null) {
+      jumpTable =
+          IndexedDISI.createJumpTable(
+              data,
+              entry.docsWithFieldOffset,
+              entry.docsWithFieldLength,
+              entry.jumpTableEntryCount);
+      if (merging) {
+        disiJumpTables.put(field.number, jumpTable);
+      }
+    }
+    return jumpTable;
+  }
+
+  @Override
+  public NumericDocValues getNorms(FieldInfo field) throws IOException {
+    final NormsEntry entry = norms.get(field.number);
+    if (entry.docsWithFieldOffset == -2) {
+      // empty
+      return DocValues.emptyNumeric();
+    } else if (entry.docsWithFieldOffset == -1) {
+      // dense
+      if (entry.bytesPerNorm == 0) {
+        return new DenseNormsIterator(maxDoc) {
+          @Override
+          public long longValue() throws IOException {
+            return entry.normsOffset;
+          }
+        };
+      }
+      final RandomAccessInput slice = getDataInput(field, entry);
+      switch (entry.bytesPerNorm) {
+        case 1:
+          return new DenseNormsIterator(maxDoc) {
+            @Override
+            public long longValue() throws IOException {
+              return slice.readByte(doc);
+            }
+          };
+        case 2:
+          return new DenseNormsIterator(maxDoc) {
+            @Override
+            public long longValue() throws IOException {
+              return slice.readShort(((long) doc) << 1);
+            }
+          };
+        case 4:
+          return new DenseNormsIterator(maxDoc) {
+            @Override
+            public long longValue() throws IOException {
+              return slice.readInt(((long) doc) << 2);
+            }
+          };
+        case 8:
+          return new DenseNormsIterator(maxDoc) {
+            @Override
+            public long longValue() throws IOException {
+              return slice.readLong(((long) doc) << 3);
+            }
+          };
+        default:
+          // should not happen, we already validate bytesPerNorm in readFields
+          throw new AssertionError();
+      }
+    } else {
+      // sparse
+      final IndexInput disiInput = getDisiInput(field, entry);
+      final RandomAccessInput disiJumpTable = getDisiJumpTable(field, entry);
+      final IndexedDISI disi =
+          new IndexedDISI(
+              disiInput,
+              disiJumpTable,
+              entry.jumpTableEntryCount,
+              entry.denseRankPower,
+              entry.numDocsWithField);
+
+      if (entry.bytesPerNorm == 0) {
+        return new SparseNormsIterator(disi) {
+          @Override
+          public long longValue() throws IOException {
+            return entry.normsOffset;
+          }
+        };
+      }
+      final RandomAccessInput slice = getDataInput(field, entry);
+      switch (entry.bytesPerNorm) {
+        case 1:
+          return new SparseNormsIterator(disi) {
+            @Override
+            public long longValue() throws IOException {
+              return slice.readByte(disi.index());
+            }
+          };
+        case 2:
+          return new SparseNormsIterator(disi) {
+            @Override
+            public long longValue() throws IOException {
+              return slice.readShort(((long) disi.index()) << 1);
+            }
+          };
+        case 4:
+          return new SparseNormsIterator(disi) {
+            @Override
+            public long longValue() throws IOException {
+              return slice.readInt(((long) disi.index()) << 2);
+            }
+          };
+        case 8:
+          return new SparseNormsIterator(disi) {
+            @Override
+            public long longValue() throws IOException {
+              return slice.readLong(((long) disi.index()) << 3);
+            }
+          };
+        default:
+          // should not happen, we already validate bytesPerNorm in readFields
+          throw new AssertionError();
+      }
+    }
+  }
+
+  @Override
+  public void close() throws IOException {
+    data.close();
+  }
+
+  @Override
+  public long ramBytesUsed() {
+    return 64L * norms.size(); // good enough
+  }
+
+  @Override
+  public void checkIntegrity() throws IOException {
+    CodecUtil.checksumEntireFile(data);
+  }
+
+  @Override
+  public String toString() {
+    return getClass().getSimpleName() + "(fields=" + norms.size() + ")";
+  }
+}

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

@@ -162,14 +162,14 @@
  *   <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.lucene80.Lucene80NormsFormat Normalization factors}. For
+ *   <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.lucene50.Lucene50TermVectorsFormat Term Vectors}. For each
  *       field in each document, the term vector (sometimes called document vector) may be stored. A
  *       term vector consists of term text and term frequency. To add Term Vectors to your index see
  *       the {@link org.apache.lucene.document.Field Field} constructors
- *   <li>{@link org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat Per-document values}. Like
+ *   <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
@@ -280,12 +280,12 @@
  * <td>Stores additional per-position metadata information such as character offsets and user payloads</td>
  * </tr>
  * <tr>
- * <td>{@link org.apache.lucene.codecs.lucene80.Lucene80NormsFormat Norms}</td>
+ * <td>{@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.lucene80.Lucene80DocValuesFormat Per-Document Values}</td>
+ * <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>

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

@@ -13,4 +13,4 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat
+org.apache.lucene.codecs.lucene90.Lucene90DocValuesFormat

lucene/core/src/test/org/apache/lucene/codecs/lucene80/TestLucene90NormsFormat.java

@@ -0,0 +1,31 @@
+/*
+ * 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.lucene80;
+
+import org.apache.lucene.codecs.Codec;
+import org.apache.lucene.index.BaseNormsFormatTestCase;
+import org.apache.lucene.util.TestUtil;
+
+/** Tests Lucene90NormsFormat */
+public class TestLucene90NormsFormat extends BaseNormsFormatTestCase {
+  private final Codec codec = TestUtil.getDefaultCodec();
+
+  @Override
+  protected Codec getCodec() {
+    return codec;
+  }
+}

lucene/core/src/test/org/apache/lucene/codecs/lucene80/TestLucene90NormsFormatMergeInstance.java

@@ -0,0 +1,26 @@
+/*
+ * 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.lucene80;
+
+/** Test the merge instance of the Lucene90 norms format. */
+public class TestLucene90NormsFormatMergeInstance extends TestLucene90NormsFormat {
+
+  @Override
+  protected boolean shouldTestMergeInstance() {
+    return true;
+  }
+}

lucene/core/src/test/org/apache/lucene/codecs/lucene90/BaseLucene90DocValuesFormatTestCase.java

@@ -0,0 +1,764 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.codecs.lucene90;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.TreeSet;
+import java.util.function.LongSupplier;
+import java.util.function.Supplier;
+import org.apache.lucene.analysis.MockAnalyzer;
+import org.apache.lucene.codecs.DocValuesFormat;
+import org.apache.lucene.codecs.PostingsFormat;
+import org.apache.lucene.codecs.asserting.AssertingCodec;
+import org.apache.lucene.codecs.perfield.PerFieldDocValuesFormat;
+import org.apache.lucene.document.BinaryDocValuesField;
+import org.apache.lucene.document.Document;
+import org.apache.lucene.document.Field;
+import org.apache.lucene.document.NumericDocValuesField;
+import org.apache.lucene.document.SortedDocValuesField;
+import org.apache.lucene.document.SortedNumericDocValuesField;
+import org.apache.lucene.document.SortedSetDocValuesField;
+import org.apache.lucene.document.StoredField;
+import org.apache.lucene.document.StringField;
+import org.apache.lucene.index.BaseCompressingDocValuesFormatTestCase;
+import org.apache.lucene.index.BinaryDocValues;
+import org.apache.lucene.index.DirectoryReader;
+import org.apache.lucene.index.DocValues;
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.IndexWriter;
+import org.apache.lucene.index.IndexWriterConfig;
+import org.apache.lucene.index.IndexableField;
+import org.apache.lucene.index.LeafReader;
+import org.apache.lucene.index.LeafReaderContext;
+import org.apache.lucene.index.NumericDocValues;
+import org.apache.lucene.index.RandomIndexWriter;
+import org.apache.lucene.index.SerialMergeScheduler;
+import org.apache.lucene.index.SortedDocValues;
+import org.apache.lucene.index.SortedNumericDocValues;
+import org.apache.lucene.index.SortedSetDocValues;
+import org.apache.lucene.index.Term;
+import org.apache.lucene.index.Terms;
+import org.apache.lucene.index.TermsEnum;
+import org.apache.lucene.index.TermsEnum.SeekStatus;
+import org.apache.lucene.store.ByteBuffersDataInput;
+import org.apache.lucene.store.ByteBuffersDataOutput;
+import org.apache.lucene.store.Directory;
+import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.BytesRefBuilder;
+import org.apache.lucene.util.TestUtil;
+
+/** Tests Lucene90DocValuesFormat */
+public abstract class BaseLucene90DocValuesFormatTestCase
+    extends BaseCompressingDocValuesFormatTestCase {
+
+  // TODO: these big methods can easily blow up some of the other ram-hungry codecs...
+  // for now just keep them here, as we want to test this for this format.
+
+  public void testSortedSetVariableLengthBigVsStoredFields() throws Exception {
+    int numIterations = atLeast(1);
+    for (int i = 0; i < numIterations; i++) {
+      int numDocs = TEST_NIGHTLY ? atLeast(100) : atLeast(10);
+      doTestSortedSetVsStoredFields(numDocs, 1, 32766, 16, 100);
+    }
+  }
+
+  @Nightly
+  public void testSortedSetVariableLengthManyVsStoredFields() throws Exception {
+    int numIterations = atLeast(1);
+    for (int i = 0; i < numIterations; i++) {
+      doTestSortedSetVsStoredFields(TestUtil.nextInt(random(), 1024, 2049), 1, 500, 16, 100);
+    }
+  }
+
+  @Slow
+  public void testSortedVariableLengthBigVsStoredFields() throws Exception {
+    int numIterations = atLeast(1);
+    for (int i = 0; i < numIterations; i++) {
+      doTestSortedVsStoredFields(atLeast(100), 1d, 1, 32766);
+    }
+  }
+
+  @Nightly
+  public void testSortedVariableLengthManyVsStoredFields() throws Exception {
+    int numIterations = atLeast(1);
+    for (int i = 0; i < numIterations; i++) {
+      doTestSortedVsStoredFields(TestUtil.nextInt(random(), 1024, 2049), 1d, 1, 500);
+    }
+  }
+
+  @Nightly
+  public void testTermsEnumFixedWidth() throws Exception {
+    int numIterations = atLeast(1);
+    for (int i = 0; i < numIterations; i++) {
+      doTestTermsEnumRandom(
+          TestUtil.nextInt(random(), 1025, 5121),
+          () -> TestUtil.randomSimpleString(random(), 10, 10));
+    }
+  }
+
+  @Nightly
+  public void testTermsEnumVariableWidth() throws Exception {
+    int numIterations = atLeast(1);
+    for (int i = 0; i < numIterations; i++) {
+      doTestTermsEnumRandom(
+          TestUtil.nextInt(random(), 1025, 5121),
+          () -> TestUtil.randomSimpleString(random(), 1, 500));
+    }
+  }
+
+  @Nightly
+  public void testTermsEnumRandomMany() throws Exception {
+    int numIterations = atLeast(1);
+    for (int i = 0; i < numIterations; i++) {
+      doTestTermsEnumRandom(
+          TestUtil.nextInt(random(), 1025, 8121),
+          () -> TestUtil.randomSimpleString(random(), 1, 500));
+    }
+  }
+
+  @Nightly
+  public void testTermsEnumLongSharedPrefixes() throws Exception {
+    int numIterations = atLeast(1);
+    for (int i = 0; i < numIterations; i++) {
+      doTestTermsEnumRandom(
+          TestUtil.nextInt(random(), 1025, 5121),
+          () -> {
+            char[] chars = new char[random().nextInt(500)];
+            Arrays.fill(chars, 'a');
+            if (chars.length > 0) {
+              chars[random().nextInt(chars.length)] = 'b';
+            }
+            return new String(chars);
+          });
+    }
+  }
+
+  @Slow
+  public void testSparseDocValuesVsStoredFields() throws Exception {
+    int numIterations = atLeast(1);
+    for (int i = 0; i < numIterations; i++) {
+      doTestSparseDocValuesVsStoredFields();
+    }
+  }
+
+  private void doTestSparseDocValuesVsStoredFields() throws Exception {
+    final long[] values = new long[TestUtil.nextInt(random(), 1, 500)];
+    for (int i = 0; i < values.length; ++i) {
+      values[i] = random().nextLong();
+    }
+
+    Directory dir = newFSDirectory(createTempDir());
+    IndexWriterConfig conf = newIndexWriterConfig(new MockAnalyzer(random()));
+    conf.setMergeScheduler(new SerialMergeScheduler());
+    RandomIndexWriter writer = new RandomIndexWriter(random(), dir, conf);
+
+    // sparse compression is only enabled if less than 1% of docs have a value
+    final int avgGap = 100;
+
+    final int numDocs = atLeast(200);
+    for (int i = random().nextInt(avgGap * 2); i >= 0; --i) {
+      writer.addDocument(new Document());
+    }
+    final int maxNumValuesPerDoc = random().nextBoolean() ? 1 : TestUtil.nextInt(random(), 2, 5);
+    for (int i = 0; i < numDocs; ++i) {
+      Document doc = new Document();
+
+      // single-valued
+      long docValue = values[random().nextInt(values.length)];
+      doc.add(new NumericDocValuesField("numeric", docValue));
+      doc.add(new SortedDocValuesField("sorted", new BytesRef(Long.toString(docValue))));
+      doc.add(new BinaryDocValuesField("binary", new BytesRef(Long.toString(docValue))));
+      doc.add(new StoredField("value", docValue));
+
+      // multi-valued
+      final int numValues = TestUtil.nextInt(random(), 1, maxNumValuesPerDoc);
+      for (int j = 0; j < numValues; ++j) {
+        docValue = values[random().nextInt(values.length)];
+        doc.add(new SortedNumericDocValuesField("sorted_numeric", docValue));
+        doc.add(new SortedSetDocValuesField("sorted_set", new BytesRef(Long.toString(docValue))));
+        doc.add(new StoredField("values", docValue));
+      }
+
+      writer.addDocument(doc);
+
+      // add a gap
+      for (int j = TestUtil.nextInt(random(), 0, avgGap * 2); j >= 0; --j) {
+        writer.addDocument(new Document());
+      }
+    }
+
+    if (random().nextBoolean()) {
+      writer.forceMerge(1);
+    }
+
+    final IndexReader indexReader = writer.getReader();
+    writer.close();
+
+    for (LeafReaderContext context : indexReader.leaves()) {
+      final LeafReader reader = context.reader();
+      final NumericDocValues numeric = DocValues.getNumeric(reader, "numeric");
+
+      final SortedDocValues sorted = DocValues.getSorted(reader, "sorted");
+
+      final BinaryDocValues binary = DocValues.getBinary(reader, "binary");
+
+      final SortedNumericDocValues sortedNumeric =
+          DocValues.getSortedNumeric(reader, "sorted_numeric");
+
+      final SortedSetDocValues sortedSet = DocValues.getSortedSet(reader, "sorted_set");
+
+      for (int i = 0; i < reader.maxDoc(); ++i) {
+        final Document doc = reader.document(i);
+        final IndexableField valueField = doc.getField("value");
+        final Long value = valueField == null ? null : valueField.numericValue().longValue();
+
+        if (value == null) {
+          assertTrue(numeric.docID() + " vs " + i, numeric.docID() < i);
+        } else {
+          assertEquals(i, numeric.nextDoc());
+          assertEquals(i, binary.nextDoc());
+          assertEquals(i, sorted.nextDoc());
+          assertEquals(value.longValue(), numeric.longValue());
+          assertTrue(sorted.ordValue() >= 0);
+          assertEquals(new BytesRef(Long.toString(value)), sorted.lookupOrd(sorted.ordValue()));
+          assertEquals(new BytesRef(Long.toString(value)), binary.binaryValue());
+        }
+
+        final IndexableField[] valuesFields = doc.getFields("values");
+        if (valuesFields.length == 0) {
+          assertTrue(sortedNumeric.docID() + " vs " + i, sortedNumeric.docID() < i);
+        } else {
+          final Set<Long> valueSet = new HashSet<>();
+          for (IndexableField sf : valuesFields) {
+            valueSet.add(sf.numericValue().longValue());
+          }
+
+          assertEquals(i, sortedNumeric.nextDoc());
+          assertEquals(valuesFields.length, sortedNumeric.docValueCount());
+          for (int j = 0; j < sortedNumeric.docValueCount(); ++j) {
+            assertTrue(valueSet.contains(sortedNumeric.nextValue()));
+          }
+          assertEquals(i, sortedSet.nextDoc());
+          int sortedSetCount = 0;
+          while (true) {
+            long ord = sortedSet.nextOrd();
+            if (ord == SortedSetDocValues.NO_MORE_ORDS) {
+              break;
+            }
+            assertTrue(valueSet.contains(Long.parseLong(sortedSet.lookupOrd(ord).utf8ToString())));
+            sortedSetCount++;
+          }
+          assertEquals(valueSet.size(), sortedSetCount);
+        }
+      }
+    }
+
+    indexReader.close();
+    dir.close();
+  }
+
+  // TODO: try to refactor this and some termsenum tests into the base class.
+  // to do this we need to fix the test class to get a DVF not a Codec so we can setup
+  // the postings format correctly.
+  private void doTestTermsEnumRandom(int numDocs, Supplier<String> valuesProducer)
+      throws Exception {
+    Directory dir = newFSDirectory(createTempDir());
+    IndexWriterConfig conf = newIndexWriterConfig(new MockAnalyzer(random()));
+    conf.setMergeScheduler(new SerialMergeScheduler());
+    // set to duel against a codec which has ordinals:
+    final PostingsFormat pf = TestUtil.getPostingsFormatWithOrds(random());
+    final DocValuesFormat dv =
+        ((PerFieldDocValuesFormat) getCodec().docValuesFormat())
+            .getDocValuesFormatForField("random_field_name");
+    conf.setCodec(
+        new AssertingCodec() {
+          @Override
+          public PostingsFormat getPostingsFormatForField(String field) {
+            return pf;
+          }
+
+          @Override
+          public DocValuesFormat getDocValuesFormatForField(String field) {
+            return dv;
+          }
+        });
+    RandomIndexWriter writer = new RandomIndexWriter(random(), dir, conf);
+
+    // index some docs
+    for (int i = 0; i < numDocs; i++) {
+      Document doc = new Document();
+      Field idField = new StringField("id", Integer.toString(i), Field.Store.NO);
+      doc.add(idField);
+      int numValues = random().nextInt(17);
+      // create a random list of strings
+      List<String> values = new ArrayList<>();
+      for (int v = 0; v < numValues; v++) {
+        values.add(valuesProducer.get());
+      }
+
+      // add in any order to the indexed field
+      ArrayList<String> unordered = new ArrayList<>(values);
+      Collections.shuffle(unordered, random());
+      for (String v : values) {
+        doc.add(newStringField("indexed", v, Field.Store.NO));
+      }
+
+      // add in any order to the dv field
+      ArrayList<String> unordered2 = new ArrayList<>(values);
+      Collections.shuffle(unordered2, random());
+      for (String v : unordered2) {
+        doc.add(new SortedSetDocValuesField("dv", new BytesRef(v)));
+      }
+
+      writer.addDocument(doc);
+      if (random().nextInt(31) == 0) {
+        writer.commit();
+      }
+    }
+
+    // delete some docs
+    int numDeletions = random().nextInt(numDocs / 10);
+    for (int i = 0; i < numDeletions; i++) {
+      int id = random().nextInt(numDocs);
+      writer.deleteDocuments(new Term("id", Integer.toString(id)));
+    }
+
+    // compare per-segment
+    DirectoryReader ir = writer.getReader();
+    for (LeafReaderContext context : ir.leaves()) {
+      LeafReader r = context.reader();
+      Terms terms = r.terms("indexed");
+      if (terms != null) {
+        SortedSetDocValues ssdv = r.getSortedSetDocValues("dv");
+        assertEquals(terms.size(), ssdv.getValueCount());
+        TermsEnum expected = terms.iterator();
+        TermsEnum actual = r.getSortedSetDocValues("dv").termsEnum();
+        assertEquals(terms.size(), expected, actual);
+
+        doTestSortedSetEnumAdvanceIndependently(ssdv);
+      }
+    }
+    ir.close();
+
+    writer.forceMerge(1);
+
+    // now compare again after the merge
+    ir = writer.getReader();
+    LeafReader ar = getOnlyLeafReader(ir);
+    Terms terms = ar.terms("indexed");
+    if (terms != null) {
+      assertEquals(terms.size(), ar.getSortedSetDocValues("dv").getValueCount());
+      TermsEnum expected = terms.iterator();
+      TermsEnum actual = ar.getSortedSetDocValues("dv").termsEnum();
+      assertEquals(terms.size(), expected, actual);
+    }
+    ir.close();
+
+    writer.close();
+    dir.close();
+  }
+
+  private void assertEquals(long numOrds, TermsEnum expected, TermsEnum actual) throws Exception {
+    BytesRef ref;
+
+    // sequential next() through all terms
+    while ((ref = expected.next()) != null) {
+      assertEquals(ref, actual.next());
+      assertEquals(expected.ord(), actual.ord());
+      assertEquals(expected.term(), actual.term());
+    }
+    assertNull(actual.next());
+
+    // sequential seekExact(ord) through all terms
+    for (long i = 0; i < numOrds; i++) {
+      expected.seekExact(i);
+      actual.seekExact(i);
+      assertEquals(expected.ord(), actual.ord());
+      assertEquals(expected.term(), actual.term());
+    }
+
+    // sequential seekExact(BytesRef) through all terms
+    for (long i = 0; i < numOrds; i++) {
+      expected.seekExact(i);
+      assertTrue(actual.seekExact(expected.term()));
+      assertEquals(expected.ord(), actual.ord());
+      assertEquals(expected.term(), actual.term());
+    }
+
+    // sequential seekCeil(BytesRef) through all terms
+    for (long i = 0; i < numOrds; i++) {
+      expected.seekExact(i);
+      assertEquals(SeekStatus.FOUND, actual.seekCeil(expected.term()));
+      assertEquals(expected.ord(), actual.ord());
+      assertEquals(expected.term(), actual.term());
+    }
+
+    // random seekExact(ord)
+    for (long i = 0; i < numOrds; i++) {
+      long randomOrd = TestUtil.nextLong(random(), 0, numOrds - 1);
+      expected.seekExact(randomOrd);
+      actual.seekExact(randomOrd);
+      assertEquals(expected.ord(), actual.ord());
+      assertEquals(expected.term(), actual.term());
+    }
+
+    // random seekExact(BytesRef)
+    for (long i = 0; i < numOrds; i++) {
+      long randomOrd = TestUtil.nextLong(random(), 0, numOrds - 1);
+      expected.seekExact(randomOrd);
+      actual.seekExact(expected.term());
+      assertEquals(expected.ord(), actual.ord());
+      assertEquals(expected.term(), actual.term());
+    }
+
+    // random seekCeil(BytesRef)
+    for (long i = 0; i < numOrds; i++) {
+      BytesRef target = new BytesRef(TestUtil.randomUnicodeString(random()));
+      SeekStatus expectedStatus = expected.seekCeil(target);
+      assertEquals(expectedStatus, actual.seekCeil(target));
+      if (expectedStatus != SeekStatus.END) {
+        assertEquals(expected.ord(), actual.ord());
+        assertEquals(expected.term(), actual.term());
+      }
+    }
+  }
+
+  @Nightly
+  public void testSortedSetAroundBlockSize() throws IOException {
+    final int frontier = 1 << Lucene90DocValuesFormat.DIRECT_MONOTONIC_BLOCK_SHIFT;
+    for (int maxDoc = frontier - 1; maxDoc <= frontier + 1; ++maxDoc) {
+      final Directory dir = newDirectory();
+      IndexWriter w =
+          new IndexWriter(dir, newIndexWriterConfig().setMergePolicy(newLogMergePolicy()));
+      ByteBuffersDataOutput out = new ByteBuffersDataOutput();
+      Document doc = new Document();
+      SortedSetDocValuesField field1 = new SortedSetDocValuesField("sset", new BytesRef());
+      doc.add(field1);
+      SortedSetDocValuesField field2 = new SortedSetDocValuesField("sset", new BytesRef());
+      doc.add(field2);
+      for (int i = 0; i < maxDoc; ++i) {
+        BytesRef s1 = new BytesRef(TestUtil.randomSimpleString(random(), 2));
+        BytesRef s2 = new BytesRef(TestUtil.randomSimpleString(random(), 2));
+        field1.setBytesValue(s1);
+        field2.setBytesValue(s2);
+        w.addDocument(doc);
+        Set<BytesRef> set = new TreeSet<>(Arrays.asList(s1, s2));
+        out.writeVInt(set.size());
+        for (BytesRef ref : set) {
+          out.writeVInt(ref.length);
+          out.writeBytes(ref.bytes, ref.offset, ref.length);
+        }
+      }
+
+      w.forceMerge(1);
+      DirectoryReader r = DirectoryReader.open(w);
+      w.close();
+      LeafReader sr = getOnlyLeafReader(r);
+      assertEquals(maxDoc, sr.maxDoc());
+      SortedSetDocValues values = sr.getSortedSetDocValues("sset");
+      assertNotNull(values);
+      ByteBuffersDataInput in = out.toDataInput();
+      BytesRefBuilder b = new BytesRefBuilder();
+      for (int i = 0; i < maxDoc; ++i) {
+        assertEquals(i, values.nextDoc());
+        final int numValues = in.readVInt();
+
+        for (int j = 0; j < numValues; ++j) {
+          b.setLength(in.readVInt());
+          b.grow(b.length());
+          in.readBytes(b.bytes(), 0, b.length());
+          assertEquals(b.get(), values.lookupOrd(values.nextOrd()));
+        }
+
+        assertEquals(SortedSetDocValues.NO_MORE_ORDS, values.nextOrd());
+      }
+      r.close();
+      dir.close();
+    }
+  }
+
+  @Nightly
+  public void testSortedNumericAroundBlockSize() throws IOException {
+    final int frontier = 1 << Lucene90DocValuesFormat.DIRECT_MONOTONIC_BLOCK_SHIFT;
+    for (int maxDoc = frontier - 1; maxDoc <= frontier + 1; ++maxDoc) {
+      final Directory dir = newDirectory();
+      IndexWriter w =
+          new IndexWriter(dir, newIndexWriterConfig().setMergePolicy(newLogMergePolicy()));
+      ByteBuffersDataOutput buffer = new ByteBuffersDataOutput();
+
+      Document doc = new Document();
+      SortedNumericDocValuesField field1 = new SortedNumericDocValuesField("snum", 0L);
+      doc.add(field1);
+      SortedNumericDocValuesField field2 = new SortedNumericDocValuesField("snum", 0L);
+      doc.add(field2);
+      for (int i = 0; i < maxDoc; ++i) {
+        long s1 = random().nextInt(100);
+        long s2 = random().nextInt(100);
+        field1.setLongValue(s1);
+        field2.setLongValue(s2);
+        w.addDocument(doc);
+        buffer.writeVLong(Math.min(s1, s2));
+        buffer.writeVLong(Math.max(s1, s2));
+      }
+
+      w.forceMerge(1);
+      DirectoryReader r = DirectoryReader.open(w);
+      w.close();
+      LeafReader sr = getOnlyLeafReader(r);
+      assertEquals(maxDoc, sr.maxDoc());
+      SortedNumericDocValues values = sr.getSortedNumericDocValues("snum");
+      assertNotNull(values);
+      ByteBuffersDataInput dataInput = buffer.toDataInput();
+      for (int i = 0; i < maxDoc; ++i) {
+        assertEquals(i, values.nextDoc());
+        assertEquals(2, values.docValueCount());
+        assertEquals(dataInput.readVLong(), values.nextValue());
+        assertEquals(dataInput.readVLong(), values.nextValue());
+      }
+      r.close();
+      dir.close();
+    }
+  }
+
+  @Nightly
+  public void testSortedNumericBlocksOfVariousBitsPerValue() throws Exception {
+    doTestSortedNumericBlocksOfVariousBitsPerValue(() -> TestUtil.nextInt(random(), 1, 3));
+  }
+
+  @Nightly
+  public void testSparseSortedNumericBlocksOfVariousBitsPerValue() throws Exception {
+    doTestSortedNumericBlocksOfVariousBitsPerValue(() -> TestUtil.nextInt(random(), 0, 2));
+  }
+
+  @Nightly
+  public void testNumericBlocksOfVariousBitsPerValue() throws Exception {
+    doTestSparseNumericBlocksOfVariousBitsPerValue(1);
+  }
+
+  @Nightly
+  public void testSparseNumericBlocksOfVariousBitsPerValue() throws Exception {
+    doTestSparseNumericBlocksOfVariousBitsPerValue(random().nextDouble());
+  }
+
+  // The LUCENE-8585 jump-tables enables O(1) skipping of IndexedDISI blocks, DENSE block lookup
+  // and numeric multi blocks. This test focuses on testing these jumps.
+  @Nightly
+  public void testNumericFieldJumpTables() throws Exception {
+    // IndexedDISI block skipping only activated if target >= current+2, so we need at least 5
+    // blocks to
+    // trigger consecutive block skips
+    final int maxDoc = atLeast(5 * 65536);
+
+    Directory dir = newDirectory();
+    IndexWriter iw = createFastIndexWriter(dir, maxDoc);
+
+    Field idField = newStringField("id", "", Field.Store.NO);
+    Field storedField = newStringField("stored", "", Field.Store.YES);
+    Field dvField = new NumericDocValuesField("dv", 0);
+
+    for (int i = 0; i < maxDoc; i++) {
+      Document doc = new Document();
+      idField.setStringValue(Integer.toBinaryString(i));
+      doc.add(idField);
+      if (random().nextInt(100) > 10) { // Skip 10% to make DENSE blocks
+        int value = random().nextInt(100000);
+        storedField.setStringValue(Integer.toString(value));
+        doc.add(storedField);
+        dvField.setLongValue(value);
+        doc.add(dvField);
+      }
+      iw.addDocument(doc);
+    }
+    iw.flush();
+    iw.forceMerge(1, true); // Single segment to force large enough structures
+    iw.commit();
+    iw.close();
+
+    assertDVIterate(dir);
+    assertDVAdvance(
+        dir, rarely() ? 1 : 7); // 1 is heavy (~20 s), so we do it rarely. 7 is a lot faster (8 s)
+
+    dir.close();
+  }
+
+  private IndexWriter createFastIndexWriter(Directory dir, int maxBufferedDocs) throws IOException {
+    IndexWriterConfig conf = newIndexWriterConfig(new MockAnalyzer(random()));
+    conf.setMaxBufferedDocs(maxBufferedDocs);
+    conf.setRAMBufferSizeMB(-1);
+    conf.setMergePolicy(newLogMergePolicy(random().nextBoolean()));
+    return new IndexWriter(dir, conf);
+  }
+
+  private static LongSupplier blocksOfVariousBPV() {
+    final long mul = TestUtil.nextInt(random(), 1, 100);
+    final long min = random().nextInt();
+    return new LongSupplier() {
+      int i = Lucene90DocValuesFormat.NUMERIC_BLOCK_SIZE;
+      int maxDelta;
+
+      @Override
+      public long getAsLong() {
+        if (i == Lucene90DocValuesFormat.NUMERIC_BLOCK_SIZE) {
+          maxDelta = 1 << random().nextInt(5);
+          i = 0;
+        }
+        i++;
+        return min + mul * random().nextInt(maxDelta);
+      }
+    };
+  }
+
+  private void doTestSortedNumericBlocksOfVariousBitsPerValue(LongSupplier counts)
+      throws Exception {
+    Directory dir = newDirectory();
+    IndexWriterConfig conf = newIndexWriterConfig(new MockAnalyzer(random()));
+    conf.setMaxBufferedDocs(atLeast(Lucene90DocValuesFormat.NUMERIC_BLOCK_SIZE));
+    conf.setRAMBufferSizeMB(-1);
+    conf.setMergePolicy(newLogMergePolicy(random().nextBoolean()));
+    IndexWriter writer = new IndexWriter(dir, conf);
+
+    final int numDocs = atLeast(Lucene90DocValuesFormat.NUMERIC_BLOCK_SIZE * 3);
+    final LongSupplier values = blocksOfVariousBPV();
+    for (int i = 0; i < numDocs; i++) {
+      Document doc = new Document();
+
+      int valueCount = (int) counts.getAsLong();
+      long valueArray[] = new long[valueCount];
+      for (int j = 0; j < valueCount; j++) {
+        long value = values.getAsLong();
+        valueArray[j] = value;
+        doc.add(new SortedNumericDocValuesField("dv", value));
+      }
+      Arrays.sort(valueArray);
+      for (int j = 0; j < valueCount; j++) {
+        doc.add(new StoredField("stored", Long.toString(valueArray[j])));
+      }
+      writer.addDocument(doc);
+      if (random().nextInt(31) == 0) {
+        writer.commit();
+      }
+    }
+    writer.forceMerge(1);
+
+    writer.close();
+
+    // compare
+    DirectoryReader ir = DirectoryReader.open(dir);
+    TestUtil.checkReader(ir);
+    for (LeafReaderContext context : ir.leaves()) {
+      LeafReader r = context.reader();
+      SortedNumericDocValues docValues = DocValues.getSortedNumeric(r, "dv");
+      for (int i = 0; i < r.maxDoc(); i++) {
+        if (i > docValues.docID()) {
+          docValues.nextDoc();
+        }
+        String expected[] = r.document(i).getValues("stored");
+        if (i < docValues.docID()) {
+          assertEquals(0, expected.length);
+        } else {
+          String actual[] = new String[docValues.docValueCount()];
+          for (int j = 0; j < actual.length; j++) {
+            actual[j] = Long.toString(docValues.nextValue());
+          }
+          assertArrayEquals(expected, actual);
+        }
+      }
+    }
+    ir.close();
+    dir.close();
+  }
+
+  private void doTestSparseNumericBlocksOfVariousBitsPerValue(double density) throws Exception {
+    Directory dir = newDirectory();
+    IndexWriterConfig conf = newIndexWriterConfig(new MockAnalyzer(random()));
+    conf.setMaxBufferedDocs(atLeast(Lucene90DocValuesFormat.NUMERIC_BLOCK_SIZE));
+    conf.setRAMBufferSizeMB(-1);
+    conf.setMergePolicy(newLogMergePolicy(random().nextBoolean()));
+    IndexWriter writer = new IndexWriter(dir, conf);
+    Document doc = new Document();
+    Field storedField = newStringField("stored", "", Field.Store.YES);
+    Field dvField = new NumericDocValuesField("dv", 0);
+    doc.add(storedField);
+    doc.add(dvField);
+
+    final int numDocs = atLeast(Lucene90DocValuesFormat.NUMERIC_BLOCK_SIZE * 3);
+    final LongSupplier longs = blocksOfVariousBPV();
+    for (int i = 0; i < numDocs; i++) {
+      if (random().nextDouble() > density) {
+        writer.addDocument(new Document());
+        continue;
+      }
+      long value = longs.getAsLong();
+      storedField.setStringValue(Long.toString(value));
+      dvField.setLongValue(value);
+      writer.addDocument(doc);
+    }
+
+    writer.forceMerge(1);
+
+    writer.close();
+
+    // compare
+    assertDVIterate(dir);
+    assertDVAdvance(
+        dir, 1); // Tests all jump-lengths from 1 to maxDoc (quite slow ~= 1 minute for 200K docs)
+
+    dir.close();
+  }
+
+  // Tests that advanceExact does not change the outcome
+  private void assertDVAdvance(Directory dir, int jumpStep) throws IOException {
+    DirectoryReader ir = DirectoryReader.open(dir);
+    TestUtil.checkReader(ir);
+    for (LeafReaderContext context : ir.leaves()) {
+      LeafReader r = context.reader();
+
+      for (int jump = jumpStep; jump < r.maxDoc(); jump += jumpStep) {
+        // Create a new instance each time to ensure jumps from the beginning
+        NumericDocValues docValues = DocValues.getNumeric(r, "dv");
+        for (int docID = 0; docID < r.maxDoc(); docID += jump) {
+          String base =
+              "document #"
+                  + docID
+                  + "/"
+                  + r.maxDoc()
+                  + ", jumping "
+                  + jump
+                  + " from #"
+                  + (docID - jump);
+          String storedValue = r.document(docID).get("stored");
+          if (storedValue == null) {
+            assertFalse("There should be no DocValue for " + base, docValues.advanceExact(docID));
+          } else {
+            assertTrue("There should be a DocValue for " + base, docValues.advanceExact(docID));
+            assertEquals(
+                "The doc value should be correct for " + base,
+                Long.parseLong(storedValue),
+                docValues.longValue());
+          }
+        }
+      }
+    }
+    ir.close();
+  }
+}

lucene/core/src/test/org/apache/lucene/codecs/lucene90/TestBestCompressionLucene90DocValuesFormat.java

@@ -0,0 +1,33 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.codecs.lucene90;
+
+import org.apache.lucene.codecs.Codec;
+import org.apache.lucene.util.TestUtil;
+
+/** Tests Lucene90DocValuesFormat */
+public class TestBestCompressionLucene90DocValuesFormat
+    extends BaseLucene90DocValuesFormatTestCase {
+  private final Codec codec =
+      TestUtil.alwaysDocValuesFormat(
+          new Lucene90DocValuesFormat(Lucene90DocValuesFormat.Mode.BEST_COMPRESSION));
+
+  @Override
+  protected Codec getCodec() {
+    return codec;
+  }
+}

lucene/core/src/test/org/apache/lucene/codecs/lucene90/TestBestSpeedLucene90DocValuesFormat.java

@@ -0,0 +1,32 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.codecs.lucene90;
+
+import org.apache.lucene.codecs.Codec;
+import org.apache.lucene.util.TestUtil;
+
+/** Tests Lucene90DocValuesFormat */
+public class TestBestSpeedLucene90DocValuesFormat extends BaseLucene90DocValuesFormatTestCase {
+  private final Codec codec =
+      TestUtil.alwaysDocValuesFormat(
+          new Lucene90DocValuesFormat(Lucene90DocValuesFormat.Mode.BEST_SPEED));
+
+  @Override
+  protected Codec getCodec() {
+    return codec;
+  }
+}

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

@@ -0,0 +1,313 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.codecs.lucene90;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import org.apache.lucene.analysis.Analyzer;
+import org.apache.lucene.analysis.standard.StandardAnalyzer;
+import org.apache.lucene.codecs.Codec;
+import org.apache.lucene.document.Document;
+import org.apache.lucene.document.Field;
+import org.apache.lucene.document.SortedDocValuesField;
+import org.apache.lucene.document.SortedSetDocValuesField;
+import org.apache.lucene.document.StringField;
+import org.apache.lucene.index.DirectoryReader;
+import org.apache.lucene.index.IndexWriter;
+import org.apache.lucene.index.IndexWriterConfig;
+import org.apache.lucene.index.LeafReader;
+import org.apache.lucene.index.SortedDocValues;
+import org.apache.lucene.index.SortedSetDocValues;
+import org.apache.lucene.store.Directory;
+import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.LuceneTestCase;
+import org.apache.lucene.util.TestUtil;
+
+public class TestDocValuesCompression extends LuceneTestCase {
+  private final Codec bestSpeed = new Lucene90Codec(Lucene90Codec.Mode.BEST_SPEED);
+  private final Codec bestCompression = new Lucene90Codec(Lucene90Codec.Mode.BEST_COMPRESSION);
+
+  public void testTermsDictCompressionForLowCardinalityFields() throws IOException {
+    final int CARDINALITY = Lucene90DocValuesFormat.TERMS_DICT_BLOCK_COMPRESSION_THRESHOLD - 1;
+    Set<String> valuesSet = new HashSet<>();
+    for (int i = 0; i < CARDINALITY; ++i) {
+      final int length = TestUtil.nextInt(random(), 10, 30);
+      String value = TestUtil.randomSimpleString(random(), length);
+      valuesSet.add(value);
+    }
+
+    List<String> values = new ArrayList<>(valuesSet);
+    long sizeForBestSpeed = writeAndGetDocValueFileSize(bestSpeed, values);
+    long sizeForBestCompression = writeAndGetDocValueFileSize(bestCompression, values);
+
+    // Ensure terms dict data was not compressed for low-cardinality fields.
+    assertEquals(sizeForBestSpeed, sizeForBestCompression);
+  }
+
+  public void testTermsDictCompressionForHighCardinalityFields() throws IOException {
+    final int CARDINALITY = Lucene90DocValuesFormat.TERMS_DICT_BLOCK_COMPRESSION_THRESHOLD << 1;
+    Set<String> valuesSet = new HashSet<>();
+    for (int i = 0; i < CARDINALITY; ++i) {
+      final int length = TestUtil.nextInt(random(), 10, 30);
+      String value = TestUtil.randomSimpleString(random(), length);
+      // Add common suffix for better compression ratio.
+      valuesSet.add(value + "_CommonPartBetterForCompression");
+    }
+
+    List<String> values = new ArrayList<>(valuesSet);
+    long sizeForBestSpeed = writeAndGetDocValueFileSize(bestSpeed, values);
+    long sizeForBestCompression = writeAndGetDocValueFileSize(bestCompression, values);
+
+    // Compression happened.
+    assertTrue(sizeForBestCompression < sizeForBestSpeed);
+  }
+
+  public void testReseekAfterSkipDecompression() throws IOException {
+    final int CARDINALITY = (Lucene90DocValuesFormat.TERMS_DICT_BLOCK_LZ4_SIZE << 1) + 11;
+    Set<String> valueSet = new HashSet<>(CARDINALITY);
+    for (int i = 0; i < CARDINALITY; i++) {
+      valueSet.add(TestUtil.randomSimpleString(random(), 64));
+    }
+    List<String> values = new ArrayList<>(valueSet);
+    Collections.sort(values);
+    // Create one non-existent value just between block-1 and block-2.
+    String nonexistentValue =
+        values.get(Lucene90DocValuesFormat.TERMS_DICT_BLOCK_LZ4_SIZE - 1)
+            + TestUtil.randomSimpleString(random(), 64, 128);
+    int docValues = values.size();
+
+    try (Directory directory = newDirectory()) {
+      Analyzer analyzer = new StandardAnalyzer();
+      IndexWriterConfig config = new IndexWriterConfig(analyzer);
+      config.setCodec(bestCompression);
+      config.setUseCompoundFile(false);
+      IndexWriter writer = new IndexWriter(directory, config);
+      for (int i = 0; i < 280; i++) {
+        Document doc = new Document();
+        doc.add(new StringField("id", "Doc" + i, Field.Store.NO));
+        doc.add(new SortedDocValuesField("sdv", new BytesRef(values.get(i % docValues))));
+        writer.addDocument(doc);
+      }
+      writer.commit();
+      writer.forceMerge(1);
+      DirectoryReader dReader = DirectoryReader.open(writer);
+      writer.close();
+
+      LeafReader reader = getOnlyLeafReader(dReader);
+      // Check values count.
+      SortedDocValues ssdvMulti = reader.getSortedDocValues("sdv");
+      assertEquals(docValues, ssdvMulti.getValueCount());
+
+      // Seek to first block.
+      int ord1 = ssdvMulti.lookupTerm(new BytesRef(values.get(0)));
+      assertTrue(ord1 >= 0);
+      int ord2 = ssdvMulti.lookupTerm(new BytesRef(values.get(1)));
+      assertTrue(ord2 >= ord1);
+      // Ensure re-seek logic is correct after skip-decompression.
+      int nonexistentOrd2 = ssdvMulti.lookupTerm(new BytesRef(nonexistentValue));
+      assertTrue(nonexistentOrd2 < 0);
+      dReader.close();
+    }
+  }
+
+  public void testLargeTermsCompression() throws IOException {
+    final int CARDINALITY = Lucene90DocValuesFormat.TERMS_DICT_BLOCK_COMPRESSION_THRESHOLD << 1;
+    Set<String> valuesSet = new HashSet<>();
+    for (int i = 0; i < CARDINALITY; ++i) {
+      final int length = TestUtil.nextInt(random(), 512, 1024);
+      valuesSet.add(TestUtil.randomSimpleString(random(), length));
+    }
+    int valuesCount = valuesSet.size();
+    List<String> values = new ArrayList<>(valuesSet);
+
+    try (Directory directory = newDirectory()) {
+      Analyzer analyzer = new StandardAnalyzer();
+      IndexWriterConfig config = new IndexWriterConfig(analyzer);
+      config.setCodec(bestCompression);
+      config.setUseCompoundFile(false);
+      IndexWriter writer = new IndexWriter(directory, config);
+      for (int i = 0; i < 256; i++) {
+        Document doc = new Document();
+        doc.add(new StringField("id", "Doc" + i, Field.Store.NO));
+        doc.add(new SortedDocValuesField("sdv", new BytesRef(values.get(i % valuesCount))));
+        writer.addDocument(doc);
+      }
+      writer.commit();
+      writer.forceMerge(1);
+      DirectoryReader ireader = DirectoryReader.open(writer);
+      writer.close();
+
+      LeafReader reader = getOnlyLeafReader(ireader);
+      // Check values count.
+      SortedDocValues ssdvMulti = reader.getSortedDocValues("sdv");
+      assertEquals(valuesCount, ssdvMulti.getValueCount());
+      ireader.close();
+    }
+  }
+
+  // Ensure the old segment can be merged together with the new compressed segment.
+  public void testMergeWithUncompressedSegment() throws IOException {
+    final int CARDINALITY = Lucene90DocValuesFormat.TERMS_DICT_BLOCK_COMPRESSION_THRESHOLD << 1;
+    Set<String> valuesSet = new HashSet<>();
+    for (int i = 0; i < CARDINALITY; ++i) {
+      final int length = TestUtil.nextInt(random(), 10, 30);
+      // Add common suffix for better compression ratio.
+      valuesSet.add(TestUtil.randomSimpleString(random(), length));
+    }
+    List<String> values = new ArrayList<>(valuesSet);
+    int valuesCount = values.size();
+
+    try (Directory directory = newDirectory()) {
+      // 1. Write 256 documents without terms dict compression.
+      Analyzer analyzer = new StandardAnalyzer();
+      IndexWriterConfig config = new IndexWriterConfig(analyzer);
+      config.setCodec(bestSpeed);
+      config.setUseCompoundFile(false);
+      IndexWriter writer = new IndexWriter(directory, config);
+      for (int i = 0; i < 256; i++) {
+        Document doc = new Document();
+        doc.add(new StringField("id", "Doc" + i, Field.Store.NO));
+        doc.add(new SortedSetDocValuesField("ssdv", new BytesRef(values.get(i % valuesCount))));
+        doc.add(
+            new SortedSetDocValuesField("ssdv", new BytesRef(values.get((i + 1) % valuesCount))));
+        doc.add(
+            new SortedSetDocValuesField("ssdv", new BytesRef(values.get((i + 2) % valuesCount))));
+        doc.add(new SortedDocValuesField("sdv", new BytesRef(values.get(i % valuesCount))));
+        writer.addDocument(doc);
+      }
+      writer.commit();
+      DirectoryReader ireader = DirectoryReader.open(writer);
+      assertEquals(256, ireader.numDocs());
+      LeafReader reader = getOnlyLeafReader(ireader);
+      SortedSetDocValues ssdv = reader.getSortedSetDocValues("ssdv");
+      assertEquals(valuesCount, ssdv.getValueCount());
+      SortedDocValues sdv = reader.getSortedDocValues("sdv");
+      assertEquals(valuesCount, sdv.getValueCount());
+      ireader.close();
+      writer.close();
+
+      // 2. Add another 100 documents, and enabling terms dict compression.
+      config = new IndexWriterConfig(analyzer);
+      config.setCodec(bestCompression);
+      config.setUseCompoundFile(false);
+      writer = new IndexWriter(directory, config);
+      // Add 2 new values.
+      valuesSet.add(TestUtil.randomSimpleString(random(), 10));
+      valuesSet.add(TestUtil.randomSimpleString(random(), 10));
+      values = new ArrayList<>(valuesSet);
+      valuesCount = valuesSet.size();
+
+      for (int i = 256; i < 356; i++) {
+        Document doc = new Document();
+        doc.add(new StringField("id", "Doc" + i, Field.Store.NO));
+        doc.add(new SortedSetDocValuesField("ssdv", new BytesRef(values.get(i % valuesCount))));
+        doc.add(new SortedDocValuesField("sdv", new BytesRef(values.get(i % valuesCount))));
+        writer.addDocument(doc);
+      }
+      writer.commit();
+      writer.forceMerge(1);
+      ireader = DirectoryReader.open(writer);
+      assertEquals(356, ireader.numDocs());
+      reader = getOnlyLeafReader(ireader);
+      ssdv = reader.getSortedSetDocValues("ssdv");
+      assertEquals(valuesCount, ssdv.getValueCount());
+      ireader.close();
+      writer.close();
+    }
+  }
+
+  private static long writeAndGetDocValueFileSize(Codec codec, List<String> values)
+      throws IOException {
+    int valuesCount = values.size();
+    long dvdFileSize = -1;
+    try (Directory directory = newDirectory()) {
+      Analyzer analyzer = new StandardAnalyzer();
+      IndexWriterConfig config = new IndexWriterConfig(analyzer);
+      config.setCodec(codec);
+      config.setUseCompoundFile(false);
+      IndexWriter writer = new IndexWriter(directory, config);
+      for (int i = 0; i < 256; i++) {
+        Document doc = new Document();
+        doc.add(new StringField("id", "Doc" + i, Field.Store.NO));
+        // Multi value sorted-set field.
+        doc.add(
+            new SortedSetDocValuesField("ssdv_multi_", new BytesRef(values.get(i % valuesCount))));
+        doc.add(
+            new SortedSetDocValuesField(
+                "ssdv_multi_", new BytesRef(values.get((i + 1) % valuesCount))));
+        doc.add(
+            new SortedSetDocValuesField(
+                "ssdv_multi_", new BytesRef(values.get((i + 2) % valuesCount))));
+        // Single value sorted-set field.
+        doc.add(
+            new SortedSetDocValuesField("ssdv_single_", new BytesRef(values.get(i % valuesCount))));
+        // Sorted field.
+        doc.add(new SortedDocValuesField("sdv", new BytesRef(values.get(i % valuesCount))));
+        writer.addDocument(doc);
+      }
+      writer.commit();
+      writer.forceMerge(1);
+      DirectoryReader ireader = DirectoryReader.open(writer);
+      writer.close();
+
+      LeafReader reader = getOnlyLeafReader(ireader);
+      // Check values count.
+      SortedSetDocValues ssdvMulti = reader.getSortedSetDocValues("ssdv_multi_");
+      assertEquals(valuesCount, ssdvMulti.getValueCount());
+      for (int i = 0; i < valuesCount; i++) {
+        BytesRef term = ssdvMulti.lookupOrd(i);
+        assertTrue(term.bytes.length > 0);
+      }
+      for (int i = 0; i < valuesCount; i++) {
+        for (int j = 0; j < 3; j++) {
+          assertTrue(ssdvMulti.lookupTerm(new BytesRef(values.get((i + j) % valuesCount))) >= 0);
+        }
+      }
+
+      SortedSetDocValues ssdvSingle = reader.getSortedSetDocValues("ssdv_single_");
+      assertEquals(valuesCount, ssdvSingle.getValueCount());
+      for (int i = 0; i < valuesCount; i++) {
+        assertTrue(ssdvSingle.lookupTerm(new BytesRef(values.get(i % valuesCount))) >= 0);
+      }
+
+      SortedDocValues sdv = reader.getSortedDocValues("sdv");
+      assertEquals(valuesCount, sdv.getValueCount());
+      for (int i = 0; i < valuesCount; i++) {
+        assertTrue(sdv.lookupTerm(new BytesRef(values.get(i % valuesCount))) >= 0);
+      }
+
+      dvdFileSize = docValueFileSize(directory);
+      assertTrue(dvdFileSize > 0);
+      ireader.close();
+    }
+
+    return dvdFileSize;
+  }
+
+  static long docValueFileSize(Directory d) throws IOException {
+    for (String file : d.listAll()) {
+      if (file.endsWith(Lucene90DocValuesFormat.DATA_EXTENSION)) {
+        return d.fileLength(file);
+      }
+    }
+    return -1;
+  }
+}

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

@@ -14,7 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.lucene.codecs.lucene80;
+package org.apache.lucene.codecs.lucene90;
 
 import java.io.IOException;
 import java.util.Random;

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

@@ -39,9 +39,9 @@ import org.apache.lucene.codecs.blockterms.LuceneVarGapDocFreqInterval;
 import org.apache.lucene.codecs.blockterms.LuceneVarGapFixedInterval;
 import org.apache.lucene.codecs.blocktreeords.BlockTreeOrdsPostingsFormat;
 import org.apache.lucene.codecs.bloom.TestBloomFilteredLucenePostings;
-import org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat;
 import org.apache.lucene.codecs.lucene86.Lucene86PointsReader;
 import org.apache.lucene.codecs.lucene86.Lucene86PointsWriter;
+import org.apache.lucene.codecs.lucene90.Lucene90DocValuesFormat;
 import org.apache.lucene.codecs.memory.DirectPostingsFormat;
 import org.apache.lucene.codecs.memory.FSTPostingsFormat;
 import org.apache.lucene.codecs.mockrandom.MockRandomPostingsFormat;
@@ -227,7 +227,7 @@ public class RandomCodec extends AssertingCodec {
     addDocValues(
         avoidCodecs,
         TestUtil.getDefaultDocValuesFormat(),
-        new Lucene80DocValuesFormat(Lucene80DocValuesFormat.Mode.BEST_COMPRESSION),
+        new Lucene90DocValuesFormat(Lucene90DocValuesFormat.Mode.BEST_COMPRESSION),
         new AssertingDocValuesFormat());
 
     Collections.shuffle(formats, random);

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

@@ -53,8 +53,8 @@ import org.apache.lucene.codecs.PostingsFormat;
 import org.apache.lucene.codecs.asserting.AssertingCodec;
 import org.apache.lucene.codecs.blockterms.LuceneFixedGap;
 import org.apache.lucene.codecs.blocktreeords.BlockTreeOrdsPostingsFormat;
-import org.apache.lucene.codecs.lucene80.Lucene80DocValuesFormat;
 import org.apache.lucene.codecs.lucene90.Lucene90Codec;
+import org.apache.lucene.codecs.lucene90.Lucene90DocValuesFormat;
 import org.apache.lucene.codecs.lucene90.Lucene90PostingsFormat;
 import org.apache.lucene.codecs.perfield.PerFieldDocValuesFormat;
 import org.apache.lucene.codecs.perfield.PerFieldPostingsFormat;
@@ -1252,7 +1252,7 @@ public final class TestUtil {
    * Lucene.
    */
   public static DocValuesFormat getDefaultDocValuesFormat() {
-    return new Lucene80DocValuesFormat();
+    return new Lucene90DocValuesFormat();
   }
 
   // TODO: generalize all 'test-checks-for-crazy-codecs' to