LUCENE-9955: Reduced state of stored fields readers.

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene50/compressing/Lucene50CompressingStoredFieldsReader.java

@@ -95,7 +95,6 @@ public final class Lucene50CompressingStoredFieldsReader extends StoredFieldsRea
   private final int chunkSize;
   private final int packedIntsVersion;
   private final CompressionMode compressionMode;
-  private final Decompressor decompressor;
   private final int numDocs;
   private final boolean merging;
   private final BlockState state;
@@ -114,12 +113,11 @@ private Lucene50CompressingStoredFieldsReader(
     this.chunkSize = reader.chunkSize;
     this.packedIntsVersion = reader.packedIntsVersion;
     this.compressionMode = reader.compressionMode;
-    this.decompressor = reader.decompressor.clone();
     this.numDocs = reader.numDocs;
     this.numDirtyChunks = reader.numDirtyChunks;
     this.numDirtyDocs = reader.numDirtyDocs;
     this.merging = merging;
-    this.state = new BlockState();
+    this.state = merging ? new BlockState() : null;
     this.closed = false;
   }
 
@@ -171,9 +169,8 @@ public Lucene50CompressingStoredFieldsReader(
         packedIntsVersion = fieldsStream.readVInt();
       }
 
-      decompressor = compressionMode.newDecompressor();
       this.merging = false;
-      this.state = new BlockState();
+      this.state = null;
 
       // 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
@@ -445,17 +442,10 @@ private class BlockState {
     // the start pointer at which you can read the compressed documents
     private long startPointer;
 
-    private final BytesRef spare;
-    private final BytesRef bytes;
+    private final BytesRef spare = new BytesRef();
+    private final BytesRef bytes = new BytesRef();
 
-    BlockState() {
-      if (merging) {
-        spare = new BytesRef();
-        bytes = new BytesRef();
-      } else {
-        spare = bytes = null;
-      }
-    }
+    private final Decompressor decompressor = compressionMode.newDecompressor();
 
     boolean contains(int docID) {
       return docID >= docBase && docID < docBase + chunkDocs;
@@ -609,13 +599,6 @@ SerializedDocument document(int docID) throws IOException {
       final int totalLength = Math.toIntExact(offsets[chunkDocs]);
       final int numStoredFields = Math.toIntExact(this.numStoredFields[index]);
 
-      final BytesRef bytes;
-      if (merging) {
-        bytes = this.bytes;
-      } else {
-        bytes = new BytesRef();
-      }
-
       final DataInput documentInput;
       if (length == 0) {
         // empty
@@ -690,6 +673,11 @@ public void skipBytes(long numBytes) throws IOException {
   }
 
   SerializedDocument document(int docID) throws IOException {
+    assert merging == (state != null);
+    BlockState state = this.state;
+    if (state == null) {
+      state = new BlockState();
+    }
     if (state.contains(docID) == false) {
       fieldsStream.seek(indexReader.getStartPointer(docID));
       state.reset(docID);

lucene/backward-codecs/src/java/org/apache/lucene/backward_codecs/lucene50/compressing/Lucene50CompressingTermVectorsReader.java

@@ -86,7 +86,6 @@ public final class Lucene50CompressingTermVectorsReader extends TermVectorsReade
   private final int version;
   private final int packedIntsVersion;
   private final CompressionMode compressionMode;
-  private final Decompressor decompressor;
   private final int chunkSize;
   private final int numDocs;
   private boolean closed;
@@ -102,7 +101,6 @@ private Lucene50CompressingTermVectorsReader(Lucene50CompressingTermVectorsReade
     this.indexReader = reader.indexReader.clone();
     this.packedIntsVersion = reader.packedIntsVersion;
     this.compressionMode = reader.compressionMode;
-    this.decompressor = reader.decompressor.clone();
     this.chunkSize = reader.chunkSize;
     this.numDocs = reader.numDocs;
     this.reader =
@@ -235,7 +233,6 @@ public Lucene50CompressingTermVectorsReader(
         numDirtyChunks = numDirtyDocs = -1;
       }
 
-      decompressor = compressionMode.newDecompressor();
       this.reader =
           new BlockPackedReaderIterator(vectorsStream, packedIntsVersion, PACKED_BLOCK_SIZE, 0);
 
@@ -689,6 +686,7 @@ public Fields get(int doc) throws IOException {
 
     // decompress data
     final BytesRef suffixBytes = new BytesRef();
+    final Decompressor decompressor = compressionMode.newDecompressor();
     decompressor.decompress(
         vectorsStream,
         totalLen + totalPayloadLength,

lucene/core/src/java/org/apache/lucene/codecs/compressing/Decompressor.java

@@ -21,7 +21,7 @@
 import org.apache.lucene.util.BytesRef;
 
 /** A decompressor. */
-public abstract class Decompressor implements Cloneable {
+public abstract class Decompressor {
 
   /** Sole constructor, typically called from sub-classes. */
   protected Decompressor() {}
@@ -41,7 +41,4 @@ protected Decompressor() {}
    */
   public abstract void decompress(
       DataInput in, int originalLength, int offset, int length, BytesRef bytes) throws IOException;
-
-  @Override
-  public abstract Decompressor clone();
 }

lucene/core/src/java/org/apache/lucene/codecs/lucene90/compressing/Lucene90CompressingStoredFieldsReader.java

@@ -78,7 +78,6 @@ public final class Lucene90CompressingStoredFieldsReader extends StoredFieldsRea
   private final IndexInput fieldsStream;
   private final int chunkSize;
   private final CompressionMode compressionMode;
-  private final Decompressor decompressor;
   private final int numDocs;
   private final boolean merging;
   private final BlockState state;
@@ -97,13 +96,12 @@ private Lucene90CompressingStoredFieldsReader(
     this.maxPointer = reader.maxPointer;
     this.chunkSize = reader.chunkSize;
     this.compressionMode = reader.compressionMode;
-    this.decompressor = reader.decompressor.clone();
     this.numDocs = reader.numDocs;
     this.numChunks = reader.numChunks;
     this.numDirtyChunks = reader.numDirtyChunks;
     this.numDirtyDocs = reader.numDirtyDocs;
     this.merging = merging;
-    this.state = new BlockState();
+    this.state = merging ? new BlockState() : null;
     this.closed = false;
   }
 
@@ -148,9 +146,8 @@ public Lucene90CompressingStoredFieldsReader(
 
       chunkSize = metaIn.readVInt();
 
-      decompressor = compressionMode.newDecompressor();
       this.merging = false;
-      this.state = new BlockState();
+      this.state = null;
 
       // 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
@@ -401,17 +398,10 @@ private class BlockState {
     // the start pointer at which you can read the compressed documents
     private long startPointer;
 
-    private final BytesRef spare;
-    private final BytesRef bytes;
+    private final BytesRef spare = new BytesRef();
+    private final BytesRef bytes = new BytesRef();
 
-    BlockState() {
-      if (merging) {
-        spare = new BytesRef();
-        bytes = new BytesRef();
-      } else {
-        spare = bytes = null;
-      }
-    }
+    private final Decompressor decompressor = compressionMode.newDecompressor();
 
     boolean contains(int docID) {
       return docID >= docBase && docID < docBase + chunkDocs;
@@ -522,13 +512,6 @@ SerializedDocument document(int docID) throws IOException {
       final int totalLength = Math.toIntExact(offsets[chunkDocs]);
       final int numStoredFields = Math.toIntExact(this.numStoredFields[index]);
 
-      final BytesRef bytes;
-      if (merging) {
-        bytes = this.bytes;
-      } else {
-        bytes = new BytesRef();
-      }
-
       final DataInput documentInput;
       if (length == 0) {
         // empty
@@ -602,6 +585,11 @@ public void skipBytes(long numBytes) throws IOException {
   }
 
   SerializedDocument document(int docID) throws IOException {
+    assert merging == (state != null);
+    BlockState state = this.state;
+    if (state == null) {
+      state = new BlockState();
+    }
     if (state.contains(docID) == false) {
       fieldsStream.seek(indexReader.getStartPointer(docID));
       state.reset(docID);

lucene/core/src/java/org/apache/lucene/codecs/lucene90/compressing/Lucene90CompressingTermVectorsReader.java

@@ -82,7 +82,6 @@ public final class Lucene90CompressingTermVectorsReader extends TermVectorsReade
   private final int version;
   private final int packedIntsVersion;
   private final CompressionMode compressionMode;
-  private final Decompressor decompressor;
   private final int chunkSize;
   private final int numDocs;
   private boolean closed;
@@ -99,7 +98,6 @@ private Lucene90CompressingTermVectorsReader(Lucene90CompressingTermVectorsReade
     this.indexReader = reader.indexReader.clone();
     this.packedIntsVersion = reader.packedIntsVersion;
     this.compressionMode = reader.compressionMode;
-    this.decompressor = reader.decompressor.clone();
     this.chunkSize = reader.chunkSize;
     this.numDocs = reader.numDocs;
     this.reader =
@@ -202,7 +200,6 @@ public Lucene90CompressingTermVectorsReader(
             metaIn);
       }
 
-      decompressor = compressionMode.newDecompressor();
       this.reader =
           new BlockPackedReaderIterator(vectorsStream, packedIntsVersion, PACKED_BLOCK_SIZE, 0);
 
@@ -651,6 +648,7 @@ public Fields get(int doc) throws IOException {
 
     // decompress data
     final BytesRef suffixBytes = new BytesRef();
+    final Decompressor decompressor = compressionMode.newDecompressor();
     decompressor.decompress(
         vectorsStream,
         totalLen + totalPayloadLength,