From 0d37e4dc768fdb50ba030d69447c927687a7b70f Mon Sep 17 00:00:00 2001
From: Adrien Grand <jpountz@gmail.com>
Date: Thu, 3 Sep 2020 11:37:34 +0200
Subject: [PATCH] LUCENE-9483: Disable per-thread caching of buffers for
 decompression of stored fields. (#1787)

These buffers can use lots of memory when the number of segments,
threads or both is high.
---
 .../CompressingStoredFieldsReader.java        | 20 +++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/lucene/core/src/java/org/apache/lucene/codecs/compressing/CompressingStoredFieldsReader.java b/lucene/core/src/java/org/apache/lucene/codecs/compressing/CompressingStoredFieldsReader.java
index 91916ddb951..cd9197f1a34 100644
--- a/lucene/core/src/java/org/apache/lucene/codecs/compressing/CompressingStoredFieldsReader.java
+++ b/lucene/core/src/java/org/apache/lucene/codecs/compressing/CompressingStoredFieldsReader.java
@@ -405,8 +405,17 @@ public final class CompressingStoredFieldsReader extends StoredFieldsReader {
     // the start pointer at which you can read the compressed documents
     private long startPointer;
 
-    private final BytesRef spare = new BytesRef();
-    private final BytesRef bytes = new BytesRef();
+    private final BytesRef spare;
+    private final BytesRef bytes;
+
+    BlockState() {
+      if (merging) {
+        spare = new BytesRef();
+        bytes = new BytesRef();
+      } else {
+        spare = bytes = null;
+      }
+    }
 
     boolean contains(int docID) {
       return docID >= docBase && docID < docBase + chunkDocs;
@@ -536,6 +545,13 @@ public final class CompressingStoredFieldsReader extends StoredFieldsReader {
       final int totalLength = offsets[chunkDocs];
       final int numStoredFields = this.numStoredFields[index];
 
+      final BytesRef bytes;
+      if (merging) {
+        bytes = this.bytes;
+      } else {
+        bytes = new BytesRef();
+      }
+
       final DataInput documentInput;
       if (length == 0) {
         // empty