fix for stored fields force merge regression

Signed-off-by: bharath-techie <[email protected]>

Author: bharath-techie

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

@@ -55,4 +55,11 @@ protected StoredFieldsReader() {}
   public StoredFieldsReader getMergeInstance() {
     return this;
   }
+
+  /**
+   * Optional: reset or close merge resources used in the reader
+   *
+   * <p>The default implementation is empty
+   */
+  public void finishMerge() throws IOException {}
 }

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

@@ -155,9 +155,16 @@ public int merge(MergeState mergeState) throws IOException {
       docCount++;
     }
     finish(docCount);
+    finishMerge(mergeState);
     return docCount;
   }
 
+  public void finishMerge(MergeState mergeState) throws IOException {
+    for (int i = 0; i < mergeState.storedFieldsReaders.length; i++) {
+      mergeState.storedFieldsReaders[i].finishMerge();
+    }
+  }
+
   /**
    * A visitor that adds every field it sees.
    *

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

@@ -104,6 +104,13 @@ private Lucene90CompressingStoredFieldsReader(
     this.version = reader.version;
     this.fieldInfos = reader.fieldInfos;
     this.fieldsStream = reader.fieldsStream.clone();
+    if (merging) {
+      try {
+        this.fieldsStream.updateReadAdvice(ReadAdvice.SEQUENTIAL);
+      } catch (IOException e) {
+        throw new AlreadyClosedException("failed to update read advice", e);
+      }
+    }
     this.indexReader = reader.indexReader.clone();
     this.maxPointer = reader.maxPointer;
     this.chunkSize = reader.chunkSize;
@@ -257,6 +264,11 @@ public void close() throws IOException {
     }
   }
 
+  @Override
+  public void finishMerge() throws IOException {
+    this.fieldsStream.updateReadAdvice(ReadAdvice.RANDOM);
+  }
+
   private static void readField(DataInput in, StoredFieldVisitor visitor, FieldInfo info, int bits)
       throws IOException {
     switch (bits & TYPE_MASK) {