Reduce ArrayUtil#grow in decompress (#12996)

apache · Apr 9, 2024 · 7ef18f2 · 7ef18f2
1 parent 1edda10
commit 7ef18f2
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diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
@@ -58,6 +58,8 @@ Improvements
 Optimizations
 ---------------------
 
+* GITHUB#12996: Reduce ArrayUtil#grow in decompress. (Zhang Chao)
+
 * GITHUB#13115: Short circuit queued flush check when flush on update is disabled (Prabhat Sharma)
 
 * GITHUB#13085: Remove unnecessary toString() / substring() calls to save some String allocations (Dmitry Cherniachenko)

diff --git a/lucene/core/src/java/org/apache/lucene/codecs/lucene90/LZ4WithPresetDictCompressionMode.java b/lucene/core/src/java/org/apache/lucene/codecs/lucene90/LZ4WithPresetDictCompressionMode.java
@@ -128,10 +128,12 @@ public void decompress(DataInput in, int originalLength, int offset, int length,
       }
 
       // Read blocks that intersect with the interval we need
+      if (offsetInBlock < offset + length) {
+        bytes.bytes = ArrayUtil.grow(bytes.bytes, bytes.length + offset + length - offsetInBlock);
+      }
       while (offsetInBlock < offset + length) {
         final int bytesToDecompress = Math.min(blockLength, offset + length - offsetInBlock);
         LZ4.decompress(in, bytesToDecompress, buffer, dictLength);
-        bytes.bytes = ArrayUtil.grow(bytes.bytes, bytes.length + bytesToDecompress);
         System.arraycopy(buffer, dictLength, bytes.bytes, bytes.length, bytesToDecompress);
         bytes.length += bytesToDecompress;
         offsetInBlock += blockLength;