255 lines
7.0 KiB
Go
255 lines
7.0 KiB
Go
// Copyright 2018 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package executor
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import (
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"context"
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"github.com/pingcap/failpoint"
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"github.com/pingcap/parser/model"
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"github.com/pingcap/parser/mysql"
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"github.com/pingcap/tidb/kv"
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plannercore "github.com/pingcap/tidb/planner/core"
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"github.com/pingcap/tidb/table"
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"github.com/pingcap/tidb/table/tables"
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"github.com/pingcap/tidb/tablecodec"
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"github.com/pingcap/tidb/types"
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"github.com/pingcap/tidb/util/chunk"
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"github.com/pingcap/tidb/util/codec"
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"github.com/pingcap/tidb/util/ranger"
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)
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func (b *executorBuilder) buildPointGet(p *plannercore.PointGetPlan) Executor {
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startTS, err := b.getStartTS()
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if err != nil {
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b.err = err
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return nil
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}
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e := &PointGetExecutor{
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baseExecutor: newBaseExecutor(b.ctx, p.Schema(), p.ExplainID()),
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}
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e.base().initCap = 1
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e.base().maxChunkSize = 1
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b.isSelectForUpdate = p.IsForUpdate
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e.Init(p, startTS)
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return e
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}
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// PointGetExecutor executes point select query.
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type PointGetExecutor struct {
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baseExecutor
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tblInfo *model.TableInfo
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handle int64
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idxInfo *model.IndexInfo
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idxVals []types.Datum
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startTS uint64
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snapshot kv.Snapshot
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done bool
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lock bool
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lockWaitTime int64
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}
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// Init set fields needed for PointGetExecutor reuse, this does NOT change baseExecutor field
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func (e *PointGetExecutor) Init(p *plannercore.PointGetPlan, startTs uint64) {
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e.tblInfo = p.TblInfo
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e.handle = p.Handle
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e.idxInfo = p.IndexInfo
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e.idxVals = p.IndexValues
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e.startTS = startTs
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e.done = false
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e.lock = p.Lock
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e.lockWaitTime = p.LockWaitTime
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}
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// Open implements the Executor interface.
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func (e *PointGetExecutor) Open(context.Context) error {
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return nil
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}
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// Close implements the Executor interface.
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func (e *PointGetExecutor) Close() error {
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return nil
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}
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// Next implements the Executor interface.
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func (e *PointGetExecutor) Next(ctx context.Context, req *chunk.Chunk) error {
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req.Reset()
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if e.done {
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return nil
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}
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e.done = true
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snapshotTS := e.startTS
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if e.lock {
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snapshotTS = e.ctx.GetSessionVars().TxnCtx.GetForUpdateTS()
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}
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var err error
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e.snapshot, err = e.ctx.GetStore().GetSnapshot(kv.Version{Ver: snapshotTS})
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if err != nil {
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return err
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}
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if e.ctx.GetSessionVars().GetReplicaRead().IsFollowerRead() {
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e.snapshot.SetOption(kv.ReplicaRead, kv.ReplicaReadFollower)
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}
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if e.idxInfo != nil {
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idxKey, err1 := encodeIndexKey(e.base(), e.tblInfo, e.idxInfo, e.idxVals)
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if err1 != nil && !kv.ErrNotExist.Equal(err1) {
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return err1
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}
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handleVal, err1 := e.get(ctx, idxKey)
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if err1 != nil && !kv.ErrNotExist.Equal(err1) {
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return err1
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}
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if len(handleVal) == 0 {
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return e.lockKeyIfNeeded(ctx, idxKey)
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}
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e.handle, err1 = tables.DecodeHandle(handleVal)
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if err1 != nil {
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return err1
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}
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// The injection is used to simulate following scenario:
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// 1. Session A create a point get query but pause before second time `GET` kv from backend
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// 2. Session B create an UPDATE query to update the record that will be obtained in step 1
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// 3. Then point get retrieve data from backend after step 2 finished
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// 4. Check the result
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failpoint.InjectContext(ctx, "pointGetRepeatableReadTest-step1", func() {
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if ch, ok := ctx.Value("pointGetRepeatableReadTest").(chan struct{}); ok {
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// Make `UPDATE` continue
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close(ch)
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}
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// Wait `UPDATE` finished
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failpoint.InjectContext(ctx, "pointGetRepeatableReadTest-step2", nil)
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})
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}
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key := tablecodec.EncodeRowKeyWithHandle(e.tblInfo.ID, e.handle)
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val, err := e.get(ctx, key)
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if err != nil && !kv.ErrNotExist.Equal(err) {
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return err
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}
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err = e.lockKeyIfNeeded(ctx, key)
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if err != nil {
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return err
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}
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if len(val) == 0 {
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if e.idxInfo != nil {
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return kv.ErrNotExist.GenWithStack("inconsistent extra index %s, handle %d not found in table",
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e.idxInfo.Name.O, e.handle)
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}
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return nil
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}
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return decodeRowValToChunk(e.base(), e.tblInfo, e.handle, val, req)
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}
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func (e *PointGetExecutor) lockKeyIfNeeded(ctx context.Context, key []byte) error {
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if e.lock {
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return doLockKeys(ctx, e.ctx, e.lockWaitTime, key)
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}
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return nil
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}
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func (e *PointGetExecutor) get(ctx context.Context, key kv.Key) (val []byte, err error) {
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txn, err := e.ctx.Txn(true)
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if err != nil {
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return nil, err
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}
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if txn != nil && txn.Valid() && !txn.IsReadOnly() {
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// We cannot use txn.Get directly here because the snapshot in txn and the snapshot of e.snapshot may be
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// different for pessimistic transaction.
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val, err = txn.GetMemBuffer().Get(ctx, key)
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if err == nil {
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return val, err
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}
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if !kv.IsErrNotFound(err) {
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return nil, err
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}
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// fallthrough to snapshot get.
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}
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return e.snapshot.Get(ctx, key)
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}
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func encodeIndexKey(e *baseExecutor, tblInfo *model.TableInfo, idxInfo *model.IndexInfo, idxVals []types.Datum) (_ []byte, err error) {
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sc := e.ctx.GetSessionVars().StmtCtx
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for i := range idxVals {
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colInfo := tblInfo.Columns[idxInfo.Columns[i].Offset]
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if colInfo.Tp == mysql.TypeString || colInfo.Tp == mysql.TypeVarString || colInfo.Tp == mysql.TypeVarchar {
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idxVals[i], err = ranger.HandlePadCharToFullLength(sc, &colInfo.FieldType, idxVals[i])
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} else {
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idxVals[i], err = table.CastValue(e.ctx, idxVals[i], colInfo)
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}
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if err != nil {
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return nil, err
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}
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}
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encodedIdxVals, err := codec.EncodeKey(sc, nil, idxVals...)
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if err != nil {
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return nil, err
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}
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return tablecodec.EncodeIndexSeekKey(tblInfo.ID, idxInfo.ID, encodedIdxVals), nil
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}
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func decodeRowValToChunk(e *baseExecutor, tblInfo *model.TableInfo, handle int64, rowVal []byte, chk *chunk.Chunk) error {
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colID2CutPos := make(map[int64]int, e.schema.Len())
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for _, col := range e.schema.Columns {
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if _, ok := colID2CutPos[col.ID]; !ok {
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colID2CutPos[col.ID] = len(colID2CutPos)
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}
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}
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cutVals, err := tablecodec.CutRowNew(rowVal, colID2CutPos)
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if err != nil {
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return err
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}
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if cutVals == nil {
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cutVals = make([][]byte, len(colID2CutPos))
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}
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decoder := codec.NewDecoder(chk, e.ctx.GetSessionVars().Location())
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for i, col := range e.schema.Columns {
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if tblInfo.PKIsHandle && mysql.HasPriKeyFlag(col.RetType.Flag) {
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chk.AppendInt64(i, handle)
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continue
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}
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if col.ID == model.ExtraHandleID {
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chk.AppendInt64(i, handle)
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continue
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}
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cutPos := colID2CutPos[col.ID]
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if len(cutVals[cutPos]) == 0 {
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colInfo := getColInfoByID(tblInfo, col.ID)
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d, err1 := table.GetColOriginDefaultValue(e.ctx, colInfo)
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if err1 != nil {
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return err1
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}
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chk.AppendDatum(i, &d)
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continue
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}
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_, err = decoder.DecodeOne(cutVals[cutPos], i, col.RetType)
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if err != nil {
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return err
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}
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}
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return nil
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}
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func getColInfoByID(tbl *model.TableInfo, colID int64) *model.ColumnInfo {
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for _, col := range tbl.Columns {
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if col.ID == colID {
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return col
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}
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}
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return nil
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}
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