dweiss commented on code in PR #16746:
URL: https://github.com/apache/lucene/pull/16746#discussion_r4452168388
##########
lucene/core/src/java/org/apache/lucene/util/compress/LZ4.java:
##########
@@ -133,6 +133,10 @@ public static int decompress(DataInput compressed, int
decompressedLen, byte[] d
// copying a multiple of 8 bytes can make decompression from 5% to 10%
faster
final int fastLen = (matchLen + 7) & 0xFFFFFFF8;
if (matchDec < matchLen || dOff + fastLen > destEnd) {
+ if (matchLen >= 274 && matchDec < matchLen) {
Review Comment:
Can we extract this 274 to a constant, with some explanation that it was
arrived at experimentally (and a link to this issue)?
##########
lucene/CHANGES.txt:
##########
@@ -19,6 +19,9 @@ Improvements
Optimizations
---------------------
+* GITHUB#16746: Speed up decoding long overlapping LZ4 matches using bulk
copies
+ of initialized bytes. (Andre Kurait)
+
Review Comment:
This should go into 11x and main, I think? If so, move the entry to 11x
##########
lucene/core/src/test/org/apache/lucene/util/compress/TestDecompressLZ4.java:
##########
@@ -18,9 +18,54 @@
import java.io.IOException;
import org.apache.lucene.store.ByteArrayDataInput;
+import org.apache.lucene.store.ByteBuffersDataOutput;
import org.apache.lucene.tests.util.LuceneTestCase;
+import org.apache.lucene.util.ArrayUtil;
public class TestDecompressLZ4 extends LuceneTestCase {
+ public void testOverlappingMatchesWithDictionaryAndPartialReads() throws
IOException {
Review Comment:
I don't think any human being other than just a bunch of lz4 enthusiasts can
follow this test but I trust it's fine in these times.
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