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index_lookup_join.go
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/
index_lookup_join.go
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// Copyright 2017 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package executor
import (
"fmt"
"runtime"
"sort"
"sync"
"unsafe"
"github.com/juju/errors"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/mysql"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/sessionctx/stmtctx"
"github.com/pingcap/tidb/terror"
"github.com/pingcap/tidb/types"
"github.com/pingcap/tidb/util/chunk"
"github.com/pingcap/tidb/util/codec"
"github.com/pingcap/tidb/util/memory"
"github.com/pingcap/tidb/util/mvmap"
"github.com/pingcap/tidb/util/ranger"
log "github.com/sirupsen/logrus"
"golang.org/x/net/context"
)
var _ Executor = &IndexLookUpJoin{}
// IndexLookUpJoin employs one outer worker and N innerWorkers to execute concurrently.
// It preserves the order of the outer table and support batch lookup.
//
// The execution flow is very similar to IndexLookUpReader:
// 1. outerWorker read N outer rows, build a task and send it to result channel and inner worker channel.
// 2. The innerWorker receives the task, builds key ranges from outer rows and fetch inner rows, builds inner row hash map.
// 3. main thread receives the task, waits for inner worker finish handling the task.
// 4. main thread join each outer row by look up the inner rows hash map in the task.
type IndexLookUpJoin struct {
baseExecutor
resultCh <-chan *lookUpJoinTask
cancelFunc context.CancelFunc
workerWg *sync.WaitGroup
outerCtx outerCtx
innerCtx innerCtx
task *lookUpJoinTask
joinResult *chunk.Chunk
innerIter chunk.Iterator
resultGenerator joinResultGenerator
indexRanges []*ranger.NewRange
keyOff2IdxOff []int
innerPtrBytes [][]byte
memTracker *memory.Tracker // track memory usage.
}
type outerCtx struct {
rowTypes []*types.FieldType
keyCols []int
filter expression.CNFExprs
}
type innerCtx struct {
readerBuilder *dataReaderBuilder
rowTypes []*types.FieldType
keyCols []int
}
type lookUpJoinTask struct {
outerResult *chunk.Chunk
outerMatch []bool
innerResult *chunk.List
encodedLookUpKeys *chunk.Chunk
lookupMap *mvmap.MVMap
matchedInners []chunk.Row
doneCh chan error
cursor int
memTracker *memory.Tracker // track memory usage.
}
type outerWorker struct {
outerCtx
ctx sessionctx.Context
executor Executor
executorChk *chunk.Chunk
maxBatchSize int
batchSize int
resultCh chan<- *lookUpJoinTask
innerCh chan<- *lookUpJoinTask
parentMemTracker *memory.Tracker
}
type innerWorker struct {
innerCtx
taskCh <-chan *lookUpJoinTask
outerCtx outerCtx
ctx sessionctx.Context
executorChk *chunk.Chunk
indexRanges []*ranger.NewRange
keyOff2IdxOff []int
}
// Open implements the Executor interface.
func (e *IndexLookUpJoin) Open(ctx context.Context) error {
err := e.children[0].Open(ctx)
if err != nil {
return errors.Trace(err)
}
e.memTracker = memory.NewTracker(e.id, e.ctx.GetSessionVars().MemQuotaIndexLookupJoin)
e.memTracker.AttachTo(e.ctx.GetSessionVars().StmtCtx.MemTracker)
e.innerPtrBytes = make([][]byte, 0, 8)
e.startWorkers(ctx)
return nil
}
func (e *IndexLookUpJoin) startWorkers(ctx context.Context) {
concurrency := e.ctx.GetSessionVars().IndexLookupJoinConcurrency
resultCh := make(chan *lookUpJoinTask, concurrency)
e.resultCh = resultCh
workerCtx, cancelFunc := context.WithCancel(ctx)
e.cancelFunc = cancelFunc
innerCh := make(chan *lookUpJoinTask, concurrency)
e.workerWg.Add(1)
go e.newOuterWorker(resultCh, innerCh).run(workerCtx, e.workerWg)
e.workerWg.Add(concurrency)
for i := 0; i < concurrency; i++ {
go e.newInnerWorker(innerCh).run(workerCtx, e.workerWg)
}
}
func (e *IndexLookUpJoin) newOuterWorker(resultCh, innerCh chan *lookUpJoinTask) *outerWorker {
ow := &outerWorker{
outerCtx: e.outerCtx,
ctx: e.ctx,
executor: e.children[0],
executorChk: chunk.NewChunk(e.outerCtx.rowTypes),
resultCh: resultCh,
innerCh: innerCh,
batchSize: 32,
maxBatchSize: e.ctx.GetSessionVars().IndexJoinBatchSize,
parentMemTracker: e.memTracker,
}
return ow
}
func (e *IndexLookUpJoin) newInnerWorker(taskCh chan *lookUpJoinTask) *innerWorker {
// Since multiple inner workers run concurrently, we should copy join's indexRanges for every worker to avoid data race.
copiedRanges := make([]*ranger.NewRange, 0, len(e.indexRanges))
for _, ran := range e.indexRanges {
copiedRanges = append(copiedRanges, ran.Clone())
}
iw := &innerWorker{
innerCtx: e.innerCtx,
outerCtx: e.outerCtx,
taskCh: taskCh,
ctx: e.ctx,
executorChk: chunk.NewChunk(e.innerCtx.rowTypes),
indexRanges: copiedRanges,
keyOff2IdxOff: e.keyOff2IdxOff,
}
return iw
}
// Next implements the Executor interface.
func (e *IndexLookUpJoin) Next(ctx context.Context, chk *chunk.Chunk) error {
chk.Reset()
e.joinResult.Reset()
for {
task, err := e.getFinishedTask(ctx)
if err != nil {
return errors.Trace(err)
}
if task == nil {
return nil
}
if e.innerIter == nil || e.innerIter.Current() == e.innerIter.End() {
e.lookUpMatchedInners(task, task.cursor)
e.innerIter = chunk.NewIterator4Slice(task.matchedInners)
e.innerIter.Begin()
}
outerRow := task.outerResult.GetRow(task.cursor)
if e.innerIter.Len() == 0 {
err = e.resultGenerator.emit(outerRow, nil, chk)
} else if e.innerIter.Current() != e.innerIter.End() {
err = e.resultGenerator.emit(outerRow, e.innerIter, chk)
}
if err != nil {
return errors.Trace(err)
}
if e.innerIter.Current() == e.innerIter.End() {
task.cursor++
}
if chk.NumRows() == e.maxChunkSize {
return nil
}
}
}
func (e *IndexLookUpJoin) getFinishedTask(ctx context.Context) (*lookUpJoinTask, error) {
task := e.task
if task != nil && task.cursor < task.outerResult.NumRows() {
return task, nil
}
select {
case task = <-e.resultCh:
case <-ctx.Done():
return nil, nil
}
if task == nil {
return nil, nil
}
select {
case err := <-task.doneCh:
if err != nil {
return nil, errors.Trace(err)
}
case <-ctx.Done():
return nil, nil
}
if e.task != nil {
e.task.memTracker.Detach()
}
e.task = task
return task, nil
}
func (e *IndexLookUpJoin) lookUpMatchedInners(task *lookUpJoinTask, rowIdx int) {
outerKey := task.encodedLookUpKeys.GetRow(rowIdx).GetBytes(0)
e.innerPtrBytes = task.lookupMap.Get(outerKey, e.innerPtrBytes[:0])
task.matchedInners = task.matchedInners[:0]
for _, b := range e.innerPtrBytes {
ptr := *(*chunk.RowPtr)(unsafe.Pointer(&b[0]))
matchedInner := task.innerResult.GetRow(ptr)
task.matchedInners = append(task.matchedInners, matchedInner)
}
}
func (ow *outerWorker) run(ctx context.Context, wg *sync.WaitGroup) {
defer func() {
if r := recover(); r != nil {
buf := make([]byte, 4096)
stackSize := runtime.Stack(buf, false)
buf = buf[:stackSize]
log.Errorf("outerWorker panic stack is:\n%s", buf)
task := &lookUpJoinTask{doneCh: make(chan error, 1)}
task.doneCh <- errors.Errorf("%v", r)
ow.pushToChan(ctx, task, ow.resultCh)
}
close(ow.resultCh)
close(ow.innerCh)
wg.Done()
}()
for {
task, err := ow.buildTask(ctx)
if err != nil {
task.doneCh <- errors.Trace(err)
ow.pushToChan(ctx, task, ow.resultCh)
return
}
if task == nil {
return
}
if finished := ow.pushToChan(ctx, task, ow.innerCh); finished {
return
}
if finished := ow.pushToChan(ctx, task, ow.resultCh); finished {
return
}
}
}
func (ow *outerWorker) pushToChan(ctx context.Context, task *lookUpJoinTask, dst chan<- *lookUpJoinTask) bool {
select {
case <-ctx.Done():
return true
case dst <- task:
}
return false
}
// buildTask builds a lookUpJoinTask and read outer rows.
// When err is not nil, task must not be nil to send the error to the main thread via task.
func (ow *outerWorker) buildTask(ctx context.Context) (*lookUpJoinTask, error) {
ow.executor.newChunk()
task := &lookUpJoinTask{
doneCh: make(chan error, 1),
outerResult: ow.executor.newChunk(),
encodedLookUpKeys: chunk.NewChunk([]*types.FieldType{types.NewFieldType(mysql.TypeBlob)}),
lookupMap: mvmap.NewMVMap(),
}
task.memTracker = memory.NewTracker(fmt.Sprintf("lookup join task %p", task), -1)
task.memTracker.AttachTo(ow.parentMemTracker)
ow.increaseBatchSize()
task.memTracker.Consume(task.outerResult.MemoryUsage())
for task.outerResult.NumRows() < ow.batchSize {
err := ow.executor.Next(ctx, ow.executorChk)
if err != nil {
return task, errors.Trace(err)
}
if ow.executorChk.NumRows() == 0 {
break
}
oldMemUsage := task.outerResult.MemoryUsage()
task.outerResult.Append(ow.executorChk, 0, ow.executorChk.NumRows())
newMemUsage := task.outerResult.MemoryUsage()
task.memTracker.Consume(newMemUsage - oldMemUsage)
}
if task.outerResult.NumRows() == 0 {
return nil, nil
}
if ow.filter != nil {
outerMatch := make([]bool, 0, task.outerResult.NumRows())
var err error
task.outerMatch, err = expression.VectorizedFilter(ow.ctx, ow.filter, chunk.NewIterator4Chunk(task.outerResult), outerMatch)
if err != nil {
return task, errors.Trace(err)
}
task.memTracker.Consume(int64(cap(task.outerMatch)))
}
return task, nil
}
func (ow *outerWorker) increaseBatchSize() {
if ow.batchSize < ow.maxBatchSize {
ow.batchSize *= 2
}
if ow.batchSize > ow.maxBatchSize {
ow.batchSize = ow.maxBatchSize
}
}
func (iw *innerWorker) run(ctx context.Context, wg *sync.WaitGroup) {
var task *lookUpJoinTask
defer func() {
if r := recover(); r != nil {
buf := make([]byte, 4096)
stackSize := runtime.Stack(buf, false)
buf = buf[:stackSize]
log.Errorf("innerWorker panic stack is:\n%s", buf)
// "task != nil" is guaranteed when panic happened.
task.doneCh <- errors.Errorf("%v", r)
}
wg.Done()
}()
for ok := true; ok; {
select {
case task, ok = <-iw.taskCh:
if !ok {
return
}
case <-ctx.Done():
return
}
err := iw.handleTask(ctx, task)
task.doneCh <- errors.Trace(err)
}
}
func (iw *innerWorker) handleTask(ctx context.Context, task *lookUpJoinTask) error {
dLookUpKeys, err := iw.constructDatumLookupKeys(task)
if err != nil {
return errors.Trace(err)
}
dLookUpKeys = iw.sortAndDedupDatumLookUpKeys(dLookUpKeys)
err = iw.fetchInnerResults(ctx, task, dLookUpKeys)
if err != nil {
return errors.Trace(err)
}
err = iw.buildLookUpMap(task)
if err != nil {
return errors.Trace(err)
}
return nil
}
func (iw *innerWorker) constructDatumLookupKeys(task *lookUpJoinTask) ([][]types.Datum, error) {
dLookUpKeys := make([][]types.Datum, 0, task.outerResult.NumRows())
keyBuf := make([]byte, 0, 64)
for i := 0; i < task.outerResult.NumRows(); i++ {
dLookUpKey, err := iw.constructDatumLookupKey(task, i)
if err != nil {
return nil, errors.Trace(err)
}
if dLookUpKey == nil {
// Append null to make looUpKeys the same length as outer Result.
task.encodedLookUpKeys.AppendNull(0)
continue
}
keyBuf = keyBuf[:0]
keyBuf, err = codec.EncodeKey(iw.ctx.GetSessionVars().StmtCtx, keyBuf, dLookUpKey...)
if err != nil {
return nil, errors.Trace(err)
}
// Store the encoded lookup key in chunk, so we can use it to lookup the matched inners directly.
task.encodedLookUpKeys.AppendBytes(0, keyBuf)
dLookUpKeys = append(dLookUpKeys, dLookUpKey)
}
task.memTracker.Consume(task.encodedLookUpKeys.MemoryUsage())
return dLookUpKeys, nil
}
func (iw *innerWorker) constructDatumLookupKey(task *lookUpJoinTask, rowIdx int) ([]types.Datum, error) {
if task.outerMatch != nil && !task.outerMatch[rowIdx] {
return nil, nil
}
outerRow := task.outerResult.GetRow(rowIdx)
sc := iw.ctx.GetSessionVars().StmtCtx
keyLen := len(iw.keyCols)
dLookupKey := make([]types.Datum, 0, keyLen)
for i, keyCol := range iw.outerCtx.keyCols {
outerValue := outerRow.GetDatum(keyCol, iw.outerCtx.rowTypes[keyCol])
innerColType := iw.rowTypes[iw.keyCols[i]]
innerValue, err := outerValue.ConvertTo(sc, innerColType)
if err != nil {
return nil, errors.Trace(err)
}
cmp, err := outerValue.CompareDatum(sc, &innerValue)
if err != nil {
return nil, errors.Trace(err)
}
if cmp != 0 {
// If the converted outerValue is not equal to the origin outerValue, we don't need to lookup it.
return nil, nil
}
dLookupKey = append(dLookupKey, innerValue)
}
return dLookupKey, nil
}
func (iw *innerWorker) sortAndDedupDatumLookUpKeys(dLookUpKeys [][]types.Datum) [][]types.Datum {
if len(dLookUpKeys) < 2 {
return dLookUpKeys
}
sc := iw.ctx.GetSessionVars().StmtCtx
sort.Slice(dLookUpKeys, func(i, j int) bool {
cmp := compareRow(sc, dLookUpKeys[i], dLookUpKeys[j])
return cmp < 0
})
deDupedLookupKeys := dLookUpKeys[:1]
for i := 1; i < len(dLookUpKeys); i++ {
cmp := compareRow(sc, dLookUpKeys[i], dLookUpKeys[i-1])
if cmp != 0 {
deDupedLookupKeys = append(deDupedLookupKeys, dLookUpKeys[i])
}
}
return deDupedLookupKeys
}
func compareRow(sc *stmtctx.StatementContext, left, right []types.Datum) int {
for idx := 0; idx < len(left); idx++ {
cmp, err := left[idx].CompareDatum(sc, &right[idx])
// We only compare rows with the same type, no error to return.
terror.Log(err)
if cmp > 0 {
return 1
} else if cmp < 0 {
return -1
}
}
return 0
}
func (iw *innerWorker) fetchInnerResults(ctx context.Context, task *lookUpJoinTask, dLookUpKeys [][]types.Datum) error {
innerExec, err := iw.readerBuilder.buildExecutorForIndexJoin(ctx, dLookUpKeys, iw.indexRanges, iw.keyOff2IdxOff)
if err != nil {
return errors.Trace(err)
}
defer terror.Call(innerExec.Close)
innerResult := chunk.NewList(innerExec.retTypes(), iw.ctx.GetSessionVars().MaxChunkSize)
innerResult.GetMemTracker().SetLabel("inner result")
innerResult.GetMemTracker().AttachTo(task.memTracker)
for {
err := innerExec.Next(ctx, iw.executorChk)
if err != nil {
return errors.Trace(err)
}
if iw.executorChk.NumRows() == 0 {
break
}
innerResult.Add(iw.executorChk)
iw.executorChk = chunk.NewChunk(iw.innerCtx.rowTypes)
}
task.innerResult = innerResult
return nil
}
func (iw *innerWorker) buildLookUpMap(task *lookUpJoinTask) error {
keyBuf := make([]byte, 0, 64)
valBuf := make([]byte, 8)
for i := 0; i < task.innerResult.NumChunks(); i++ {
chk := task.innerResult.GetChunk(i)
for j := 0; j < chk.NumRows(); j++ {
innerRow := chk.GetRow(j)
keyBuf = keyBuf[:0]
for _, keyCol := range iw.keyCols {
d := innerRow.GetDatum(keyCol, iw.rowTypes[keyCol])
var err error
keyBuf, err = codec.EncodeKey(iw.ctx.GetSessionVars().StmtCtx, keyBuf, d)
if err != nil {
return errors.Trace(err)
}
}
rowPtr := chunk.RowPtr{ChkIdx: uint32(i), RowIdx: uint32(j)}
*(*chunk.RowPtr)(unsafe.Pointer(&valBuf[0])) = rowPtr
task.lookupMap.Put(keyBuf, valBuf)
}
}
return nil
}
// Close implements the Executor interface.
func (e *IndexLookUpJoin) Close() error {
if e.cancelFunc != nil {
e.cancelFunc()
}
e.workerWg.Wait()
e.memTracker.Detach()
e.memTracker = nil
return errors.Trace(e.children[0].Close())
}