From 9e55944362e6971b25185c36b2d059f80bc2895e Mon Sep 17 00:00:00 2001
From: Ti Chi Robot <ti-community-prow-bot@tidb.io>
Date: Fri, 3 Nov 2023 11:59:10 +0800
Subject: [PATCH] executor: reuse chunk for GetMatchedRowsAndPtrs calls
 (#48090) (#48103)

close pingcap/tidb#48082
---
 executor/benchmark_test.go | 10 ++++++++++
 executor/hash_table.go     |  5 ++---
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/executor/benchmark_test.go b/executor/benchmark_test.go
index 5bff882e426f6..7a05282ebc9ed 100644
--- a/executor/benchmark_test.go
+++ b/executor/benchmark_test.go
@@ -1130,6 +1130,16 @@ func BenchmarkHashJoinExec(b *testing.B) {
 	b.Run(fmt.Sprintf("%v", cas), func(b *testing.B) {
 		benchmarkHashJoinExecWithCase(b, cas)
 	})
+
+	cols = []*types.FieldType{
+		types.NewFieldType(mysql.TypeLonglong),
+	}
+	cas = defaultHashJoinTestCase(cols, 0, false)
+	cas.keyIdx = []int{0}
+	cas.disk = true
+	b.Run(fmt.Sprintf("%v", cas), func(b *testing.B) {
+		benchmarkHashJoinExecWithCase(b, cas)
+	})
 }
 
 func BenchmarkOuterHashJoinExec(b *testing.B) {
diff --git a/executor/hash_table.go b/executor/hash_table.go
index 4afdef58e1973..1562b37e8014c 100644
--- a/executor/hash_table.go
+++ b/executor/hash_table.go
@@ -243,11 +243,10 @@ func (c *hashRowContainer) GetMatchedRowsAndPtrs(probeKey uint64, probeRow chunk
 	// Some variables used for memTracker.
 	var (
 		matchedDataSize                  = int64(cap(matched))*rowSize + int64(cap(matchedPtrs))*rowPtrSize
-		lastChunkBufPointer *chunk.Chunk = nil
+		lastChunkBufPointer *chunk.Chunk = c.chkBuf
 		memDelta            int64        = 0
 		needTrackMemUsage                = cap(innerPtrs) > signalCheckpointForJoinMask
 	)
-	c.chkBuf = nil
 	c.memTracker.Consume(-c.chkBufSizeForOneProbe)
 	if needTrackMemUsage {
 		c.memTracker.Consume(int64(cap(innerPtrs)) * rowPtrSize)
@@ -265,7 +264,7 @@ func (c *hashRowContainer) GetMatchedRowsAndPtrs(probeKey uint64, probeRow chunk
 		if err != nil {
 			return nil, nil, err
 		}
-		if needTrackMemUsage && c.chkBuf != lastChunkBufPointer && lastChunkBufPointer != nil {
+		if c.chkBuf != lastChunkBufPointer && lastChunkBufPointer != nil {
 			lastChunkSize := lastChunkBufPointer.MemoryUsage()
 			c.chkBufSizeForOneProbe += lastChunkSize
 			memDelta += lastChunkSize