executor: reuse iterator4Slice and Row/RowPtrs slice in HashJoin.

executor/hash_table.go

@@ -112,23 +112,24 @@ func (c *hashRowContainer) ShallowCopy() *hashRowContainer {
 // GetMatchedRowsAndPtrs get matched rows and Ptrs from probeRow. It can be called
 // in multiple goroutines while each goroutine should keep its own
 // h and buf.
-func (c *hashRowContainer) GetMatchedRowsAndPtrs(probeKey uint64, probeRow chunk.Row, hCtx *hashContext) (matched []chunk.Row, matchedPtrs []chunk.RowPtr, err error) {
+func (c *hashRowContainer) GetMatchedRowsAndPtrs(probeKey uint64, probeRow chunk.Row, hCtx *hashContext, matched []chunk.Row, matchedPtrs []chunk.RowPtr) ([]chunk.Row, []chunk.RowPtr, error) {
+	var err error
 	innerPtrs := c.hashTable.Get(probeKey)
 	if len(innerPtrs) == 0 {
-		return
+		return nil, nil, err
 	}
-	matched = make([]chunk.Row, 0, len(innerPtrs))
+	matched = matched[:0]
 	var matchedRow chunk.Row
-	matchedPtrs = make([]chunk.RowPtr, 0, len(innerPtrs))
+	matchedPtrs = matchedPtrs[:0]
 	for _, ptr := range innerPtrs {
 		matchedRow, err = c.rowContainer.GetRow(ptr)
 		if err != nil {
-			return
+			return nil, nil, err
 		}
 		var ok bool
 		ok, err = c.matchJoinKey(matchedRow, probeRow, hCtx)
 		if err != nil {
-			return
+			return nil, nil, err
 		}
 		if !ok {
 			atomic.AddInt64(&c.stat.probeCollision, 1)
@@ -137,7 +138,7 @@ func (c *hashRowContainer) GetMatchedRowsAndPtrs(probeKey uint64, probeRow chunk
 		matched = append(matched, matchedRow)
 		matchedPtrs = append(matchedPtrs, ptr)
 	}
-	return
+	return matched, matchedPtrs, err
 }
 
 // matchJoinKey checks if join keys of buildRow and probeRow are logically equal.

executor/hash_table_test.go

@@ -158,7 +158,7 @@ func testHashRowContainer(t *testing.T, hashFunc func() hash.Hash64, spill bool)
 	}
 	probeCtx.hasNull = make([]bool, 1)
 	probeCtx.hashVals = append(hCtx.hashVals, hashFunc())
-	matched, _, err := rowContainer.GetMatchedRowsAndPtrs(hCtx.hashVals[1].Sum64(), probeRow, probeCtx)
+	matched, _, err := rowContainer.GetMatchedRowsAndPtrs(hCtx.hashVals[1].Sum64(), probeRow, probeCtx, nil, nil)
 	require.NoError(t, err)
 	require.Equal(t, 2, len(matched))
 	require.Equal(t, chk0.GetRow(1).GetDatumRow(colTypes), matched[0].GetDatumRow(colTypes))

executor/join.go

@@ -94,6 +94,10 @@ type HashJoinExec struct {
 	finished            atomic.Value
 
 	stats *hashJoinRuntimeStats
+
+	// We pre-alloc and reuse the Rows and RowPtrs for each probe goroutine, to avoid allocation frequently
+	buildSideRows    [][]chunk.Row
+	buildSideRowPtrs [][]chunk.RowPtr
 }
 
 // probeChkResource stores the result of the join probe side fetch worker,
@@ -148,7 +152,8 @@ func (e *HashJoinExec) Close() error {
 		terror.Call(e.rowContainer.Close)
 	}
 	e.outerMatchedStatus = e.outerMatchedStatus[:0]
-
+	e.buildSideRows = nil
+	e.buildSideRowPtrs = nil
 	if e.stats != nil && e.rowContainer != nil {
 		e.stats.hashStat = *e.rowContainer.stat
 	}
@@ -328,6 +333,9 @@ func (e *HashJoinExec) initializeForProbe() {
 	// e.joinResultCh is for transmitting the join result chunks to the main
 	// thread.
 	e.joinResultCh = make(chan *hashjoinWorkerResult, e.concurrency+1)
+
+	e.buildSideRows = make([][]chunk.Row, e.concurrency)
+	e.buildSideRowPtrs = make([][]chunk.RowPtr, e.concurrency)
 }
 
 func (e *HashJoinExec) fetchAndProbeHashTable(ctx context.Context) {
@@ -487,7 +495,9 @@ func (e *HashJoinExec) runJoinWorker(workerID uint, probeKeyColIdx []int) {
 }
 
 func (e *HashJoinExec) joinMatchedProbeSideRow2ChunkForOuterHashJoin(workerID uint, probeKey uint64, probeSideRow chunk.Row, hCtx *hashContext, rowContainer *hashRowContainer, joinResult *hashjoinWorkerResult) (bool, *hashjoinWorkerResult) {
-	buildSideRows, rowsPtrs, err := rowContainer.GetMatchedRowsAndPtrs(probeKey, probeSideRow, hCtx)
+	var err error
+	e.buildSideRows[workerID], e.buildSideRowPtrs[workerID], err = rowContainer.GetMatchedRowsAndPtrs(probeKey, probeSideRow, hCtx, e.buildSideRows[workerID], e.buildSideRowPtrs[workerID])
+	buildSideRows, rowsPtrs := e.buildSideRows[workerID], e.buildSideRowPtrs[workerID]
 	if err != nil {
 		joinResult.err = err
 		return false, joinResult
@@ -497,6 +507,7 @@ func (e *HashJoinExec) joinMatchedProbeSideRow2ChunkForOuterHashJoin(workerID ui
 	}
 
 	iter := chunk.NewIterator4Slice(buildSideRows)
+	defer chunk.FreeIterator(iter)
 	var outerMatchStatus []outerRowStatusFlag
 	rowIdx, ok := 0, false
 	for iter.Begin(); iter.Current() != iter.End(); {
@@ -523,7 +534,9 @@ func (e *HashJoinExec) joinMatchedProbeSideRow2ChunkForOuterHashJoin(workerID ui
 }
 func (e *HashJoinExec) joinMatchedProbeSideRow2Chunk(workerID uint, probeKey uint64, probeSideRow chunk.Row, hCtx *hashContext,
 	rowContainer *hashRowContainer, joinResult *hashjoinWorkerResult) (bool, *hashjoinWorkerResult) {
-	buildSideRows, _, err := rowContainer.GetMatchedRowsAndPtrs(probeKey, probeSideRow, hCtx)
+	var err error
+	e.buildSideRows[workerID], e.buildSideRowPtrs[workerID], err = rowContainer.GetMatchedRowsAndPtrs(probeKey, probeSideRow, hCtx, e.buildSideRows[workerID], e.buildSideRowPtrs[workerID])
+	buildSideRows := e.buildSideRows[workerID]
 	if err != nil {
 		joinResult.err = err
 		return false, joinResult
@@ -533,6 +546,7 @@ func (e *HashJoinExec) joinMatchedProbeSideRow2Chunk(workerID uint, probeKey uin
 		return true, joinResult
 	}
 	iter := chunk.NewIterator4Slice(buildSideRows)
+	defer chunk.FreeIterator(iter)
 	hasMatch, hasNull, ok := false, false, false
 	for iter.Begin(); iter.Current() != iter.End(); {
 		matched, isNull, err := e.joiners[workerID].tryToMatchInners(probeSideRow, iter, joinResult.chk)

util/chunk/iterator.go

@@ -14,6 +14,8 @@
 
 package chunk
 
+import "sync"
+
 var (
 	_ Iterator = (*Iterator4Chunk)(nil)
 	_ Iterator = (*iterator4RowPtr)(nil)
@@ -23,6 +25,22 @@ var (
 	_ Iterator = (*multiIterator)(nil)
 )
 
+var (
+	iterator4SlicePool = &sync.Pool{New: func() any { return new(iterator4Slice) }}
+)
+
+// FreeIterator try to free and reuse the iterator.
+func FreeIterator(it any) {
+	switch it := it.(type) {
+	case *iterator4Slice:
+		it.rows = nil
+		it.cursor = 0
+		iterator4SlicePool.Put(it)
+	default:
+		// Do Nothing.
+	}
+}
+
 // Iterator is used to iterate a number of rows.
 //
 // for row := it.Begin(); row != it.End(); row = it.Next() {
@@ -53,7 +71,10 @@ type Iterator interface {
 
 // NewIterator4Slice returns a Iterator for Row slice.
 func NewIterator4Slice(rows []Row) Iterator {
-	return &iterator4Slice{rows: rows}
+	it := iterator4SlicePool.Get().(*iterator4Slice)
+	it.rows = rows
+	it.cursor = 0
+	return it
 }
 
 type iterator4Slice struct {