executor: control Chunk size for StreamAgg&HashAgg (pingcap#9512)

executor/aggregate.go

@@ -86,8 +86,6 @@ type HashAggFinalWorker struct {
 type AfFinalResult struct {
 	chk *chunk.Chunk
 	err error
-
-	giveBackCh chan *chunk.Chunk
 }
 
 // HashAggExec deals with all the aggregate functions.
@@ -152,6 +150,7 @@ type HashAggExec struct {
 
 	finishCh         chan struct{}
 	finalOutputCh    chan *AfFinalResult
+	finalInputCh     chan *chunk.Chunk
 	partialOutputChs []chan *HashAggIntermData
 	inputCh          chan *HashAggInput
 	partialInputChs  []chan *chunk.Chunk
@@ -247,6 +246,7 @@ func (e *HashAggExec) initForParallelExec(ctx sessionctx.Context) {
 	partialConcurrency := sessionVars.HashAggPartialConcurrency
 	e.isChildReturnEmpty = true
 	e.finalOutputCh = make(chan *AfFinalResult, finalConcurrency)
+	e.finalInputCh = make(chan *chunk.Chunk, finalConcurrency)
 	e.inputCh = make(chan *HashAggInput, partialConcurrency)
 	e.finishCh = make(chan struct{}, 1)
 
@@ -291,11 +291,10 @@ func (e *HashAggExec) initForParallelExec(ctx sessionctx.Context) {
 			groupSet:            set.NewStringSet(),
 			inputCh:             e.partialOutputChs[i],
 			outputCh:            e.finalOutputCh,
-			finalResultHolderCh: make(chan *chunk.Chunk, 1),
+			finalResultHolderCh: e.finalInputCh,
 			rowBuffer:           make([]types.Datum, 0, e.Schema().Len()),
 			mutableRow:          chunk.MutRowFromTypes(e.retTypes()),
 		}
-		e.finalWorkers[i].finalResultHolderCh <- e.newFirstChunk()
 	}
 }
 
@@ -469,7 +468,6 @@ func (w *HashAggFinalWorker) getFinalResult(sctx sessionctx.Context) {
 	if finished {
 		return
 	}
-	result.Reset()
 	for groupKey := range w.groupSet {
 		partialResults := w.getPartialResult(sctx.GetSessionVars().StmtCtx, []byte(groupKey), w.partialResultMap)
 		for i, af := range w.aggFuncs {
@@ -480,18 +478,15 @@ func (w *HashAggFinalWorker) getFinalResult(sctx sessionctx.Context) {
 		if len(w.aggFuncs) == 0 {
 			result.SetNumVirtualRows(result.NumRows() + 1)
 		}
-		if result.NumRows() == w.maxChunkSize {
-			w.outputCh <- &AfFinalResult{chk: result, giveBackCh: w.finalResultHolderCh}
+		if result.IsFull() {
+			w.outputCh <- &AfFinalResult{chk: result}
 			result, finished = w.receiveFinalResultHolder()
 			if finished {
 				return
 			}
-			result.Reset()
 		}
 	}
-	if result.NumRows() > 0 {
-		w.outputCh <- &AfFinalResult{chk: result, giveBackCh: w.finalResultHolderCh}
-	}
+	w.outputCh <- &AfFinalResult{chk: result}
 }
 
 func (w *HashAggFinalWorker) receiveFinalResultHolder() (*chunk.Chunk, bool) {
@@ -606,24 +601,30 @@ func (e *HashAggExec) parallelExec(ctx context.Context, chk *chunk.Chunk) error
 		e.prepare4ParallelExec(ctx)
 		e.prepared = true
 	}
-	for {
+
+	// gofail: var parallelHashAggError bool
+	// if parallelHashAggError {
+	// 	return errors.New("HashAggExec.parallelExec error")
+	// }
+
+	for !chk.IsFull() {
+		e.finalInputCh <- chk
 		result, ok := <-e.finalOutputCh
-		if !ok || result.err != nil || result.chk.NumRows() == 0 {
-			if result != nil {
-				return errors.Trace(result.err)
+		if !ok { // all finalWorkers exited
+			if chk.NumRows() > 0 { // but there are some data left
+				return nil
 			}
 			if e.isChildReturnEmpty && e.defaultVal != nil {
 				chk.Append(e.defaultVal, 0, 1)
 			}
 			e.isChildReturnEmpty = false
 			return nil
 		}
-		e.isChildReturnEmpty = false
-		chk.SwapColumns(result.chk)
-		// Put result.chk back to the corresponded final worker's finalResultHolderCh.
-		result.giveBackCh <- result.chk
+		if result.err != nil {
+			return result.err
+		}
 		if chk.NumRows() > 0 {
-			break
+			e.isChildReturnEmpty = false
 		}
 	}
 	return nil
@@ -657,11 +658,11 @@ func (e *HashAggExec) unparallelExec(ctx context.Context, chk *chunk.Chunk) erro
 			chk.SetNumVirtualRows(chk.NumRows() + 1)
 		}
 		for i, af := range e.PartialAggFuncs {
-			if err := (af.AppendFinalResult2Chunk(e.ctx, partialResults[i], chk)); err != nil {
+			if err := af.AppendFinalResult2Chunk(e.ctx, partialResults[i], chk); err != nil {
 				return err
 			}
 		}
-		if chk.NumRows() == e.maxChunkSize {
+		if chk.IsFull() {
 			e.cursor4GroupKey++
 			return nil
 		}
@@ -787,7 +788,7 @@ func (e *StreamAggExec) Next(ctx context.Context, chk *chunk.Chunk) error {
 		defer func() { e.runtimeStats.Record(time.Now().Sub(start), chk.NumRows()) }()
 	}
 	chk.Reset()
-	for !e.executed && chk.NumRows() < e.maxChunkSize {
+	for !e.executed && !chk.IsFull() {
 		err := e.consumeOneGroup(ctx, chk)
 		if err != nil {
 			e.executed = true