tidb/pkg/executor/point_get.go

// Copyright 2018 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,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package executor

import (
	"context"
	"fmt"
	"sort"
	"strconv"
	"time"

	"github.com/pingcap/errors"
	"github.com/pingcap/failpoint"
	"github.com/pingcap/tidb/pkg/distsql"
	"github.com/pingcap/tidb/pkg/executor/internal/exec"
	"github.com/pingcap/tidb/pkg/expression"
	"github.com/pingcap/tidb/pkg/infoschema"
	"github.com/pingcap/tidb/pkg/kv"
	"github.com/pingcap/tidb/pkg/meta/model"
	pmodel "github.com/pingcap/tidb/pkg/parser/model"
	"github.com/pingcap/tidb/pkg/parser/mysql"
	plannercore "github.com/pingcap/tidb/pkg/planner/core"
	"github.com/pingcap/tidb/pkg/sessionctx"
	"github.com/pingcap/tidb/pkg/table"
	"github.com/pingcap/tidb/pkg/table/tables"
	"github.com/pingcap/tidb/pkg/tablecodec"
	"github.com/pingcap/tidb/pkg/types"
	"github.com/pingcap/tidb/pkg/util/chunk"
	"github.com/pingcap/tidb/pkg/util/codec"
	"github.com/pingcap/tidb/pkg/util/dbterror"
	"github.com/pingcap/tidb/pkg/util/execdetails"
	"github.com/pingcap/tidb/pkg/util/intest"
	"github.com/pingcap/tidb/pkg/util/logutil/consistency"
	"github.com/pingcap/tidb/pkg/util/rowcodec"
	"github.com/tikv/client-go/v2/tikvrpc"
	"github.com/tikv/client-go/v2/txnkv/txnsnapshot"
)

func (b *executorBuilder) buildPointGet(p *plannercore.PointGetPlan) exec.Executor {
	var err error
	if err = b.validCanReadTemporaryOrCacheTable(p.TblInfo); err != nil {
		b.err = err
		return nil
	}

	if p.PrunePartitions(b.ctx) {
		// no matching partitions
		return &TableDualExec{
			BaseExecutorV2: exec.NewBaseExecutorV2(b.ctx.GetSessionVars(), p.Schema(), p.ID()),
			numDualRows:    0,
			numReturned:    0,
		}
	}

	if p.Lock && !b.inSelectLockStmt {
		b.inSelectLockStmt = true
		defer func() {
			b.inSelectLockStmt = false
		}()
	}

	e := &PointGetExecutor{
		BaseExecutor:       exec.NewBaseExecutor(b.ctx, p.Schema(), p.ID()),
		indexUsageReporter: b.buildIndexUsageReporter(p),
		txnScope:           b.txnScope,
		readReplicaScope:   b.readReplicaScope,
		isStaleness:        b.isStaleness,
		partitionNames:     p.PartitionNames,
	}

	e.SetInitCap(1)
	e.SetMaxChunkSize(1)
	e.Init(p)

	e.snapshot, err = b.getSnapshot()
	if err != nil {
		b.err = err
		return nil
	}
	if b.ctx.GetSessionVars().IsReplicaReadClosestAdaptive() {
		e.snapshot.SetOption(kv.ReplicaReadAdjuster, newReplicaReadAdjuster(e.Ctx(), p.GetAvgRowSize()))
	}
	if e.RuntimeStats() != nil {
		snapshotStats := &txnsnapshot.SnapshotRuntimeStats{}
		e.stats = &runtimeStatsWithSnapshot{
			SnapshotRuntimeStats: snapshotStats,
		}
		e.snapshot.SetOption(kv.CollectRuntimeStats, snapshotStats)
	}

	if p.IndexInfo != nil {
		sctx := b.ctx.GetSessionVars().StmtCtx
		sctx.IndexNames = append(sctx.IndexNames, p.TblInfo.Name.O+":"+p.IndexInfo.Name.O)
	}

	failpoint.Inject("assertPointReplicaOption", func(val failpoint.Value) {
		assertScope := val.(string)
		if e.Ctx().GetSessionVars().GetReplicaRead().IsClosestRead() && assertScope != e.readReplicaScope {
			panic("point get replica option fail")
		}
	})

	snapshotTS, err := b.getSnapshotTS()
	if err != nil {
		b.err = err
		return nil
	}
	if p.TblInfo.TableCacheStatusType == model.TableCacheStatusEnable {
		if cacheTable := b.getCacheTable(p.TblInfo, snapshotTS); cacheTable != nil {
			e.snapshot = cacheTableSnapshot{e.snapshot, cacheTable}
		}
	}

	if e.lock {
		b.hasLock = true
	}

	return e
}

// PointGetExecutor executes point select query.
type PointGetExecutor struct {
	exec.BaseExecutor
	indexUsageReporter *exec.IndexUsageReporter

	tblInfo          *model.TableInfo
	handle           kv.Handle
	idxInfo          *model.IndexInfo
	partitionDefIdx  *int
	partitionNames   []pmodel.CIStr
	idxKey           kv.Key
	handleVal        []byte
	idxVals          []types.Datum
	txnScope         string
	readReplicaScope string
	isStaleness      bool
	txn              kv.Transaction
	snapshot         kv.Snapshot
	done             bool
	lock             bool
	lockWaitTime     int64
	rowDecoder       *rowcodec.ChunkDecoder

	columns []*model.ColumnInfo
	// virtualColumnIndex records all the indices of virtual columns and sort them in definition
	// to make sure we can compute the virtual column in right order.
	virtualColumnIndex []int

	// virtualColumnRetFieldTypes records the RetFieldTypes of virtual columns.
	virtualColumnRetFieldTypes []*types.FieldType

	stats *runtimeStatsWithSnapshot
}

// GetPhysID returns the physical id used, either the table's id or a partition's ID
func GetPhysID(tblInfo *model.TableInfo, idx *int) int64 {
	if idx != nil {
		if *idx < 0 {
			intest.Assert(false)
		} else {
			if pi := tblInfo.GetPartitionInfo(); pi != nil {
				return pi.Definitions[*idx].ID
			}
		}
	}
	return tblInfo.ID
}

func matchPartitionNames(pid int64, partitionNames []pmodel.CIStr, pi *model.PartitionInfo) bool {
	if len(partitionNames) == 0 {
		return true
	}
	defs := pi.Definitions
	for i := range defs {
		// TODO: create a map from id to partition definition index
		if defs[i].ID == pid {
			for _, name := range partitionNames {
				if defs[i].Name.L == name.L {
					return true
				}
			}
			// Only one partition can match pid
			return false
		}
	}
	return false
}

// Recreated based on Init, change baseExecutor fields also
func (e *PointGetExecutor) Recreated(p *plannercore.PointGetPlan) {
	e.Init(p)
	// It's necessary to at least reset the `runtimeStats` of the `BaseExecutor`.
	// As the `StmtCtx` may have changed, a new index usage reporter should also be created.
	e.BaseExecutor = exec.NewBaseExecutor(e.Ctx(), p.Schema(), p.ID())
	e.indexUsageReporter = buildIndexUsageReporter(e.Ctx(), p)
}

// Init set fields needed for PointGetExecutor reuse, this does NOT change baseExecutor field
func (e *PointGetExecutor) Init(p *plannercore.PointGetPlan) {
	decoder := NewRowDecoder(e.Ctx(), p.Schema(), p.TblInfo)
	e.tblInfo = p.TblInfo
	e.handle = p.Handle
	e.idxInfo = p.IndexInfo
	e.idxVals = p.IndexValues
	e.done = false
	if e.tblInfo.TempTableType == model.TempTableNone {
		e.lock = p.Lock
		e.lockWaitTime = p.LockWaitTime
	} else {
		// Temporary table should not do any lock operations
		e.lock = false
		e.lockWaitTime = 0
	}
	e.rowDecoder = decoder
	e.partitionDefIdx = p.PartitionIdx
	e.columns = p.Columns
	e.buildVirtualColumnInfo()
}

// buildVirtualColumnInfo saves virtual column indices and sort them in definition order
func (e *PointGetExecutor) buildVirtualColumnInfo() {
	e.virtualColumnIndex = buildVirtualColumnIndex(e.Schema(), e.columns)
	if len(e.virtualColumnIndex) > 0 {
		e.virtualColumnRetFieldTypes = make([]*types.FieldType, len(e.virtualColumnIndex))
		for i, idx := range e.virtualColumnIndex {
			e.virtualColumnRetFieldTypes[i] = e.Schema().Columns[idx].RetType
		}
	}
}

// Open implements the Executor interface.
func (e *PointGetExecutor) Open(context.Context) error {
	var err error
	e.txn, err = e.Ctx().Txn(false)
	if err != nil {
		return err
	}
	if err := e.verifyTxnScope(); err != nil {
		return err
	}
	setOptionForTopSQL(e.Ctx().GetSessionVars().StmtCtx, e.snapshot)
	return nil
}

// Close implements the Executor interface.
func (e *PointGetExecutor) Close() error {
	if e.stats != nil {
		defer func() {
			sc := e.Ctx().GetSessionVars().StmtCtx
			sc.RuntimeStatsColl.RegisterStats(e.ID(), e.stats)
			timeDetail := e.stats.SnapshotRuntimeStats.GetTimeDetail()
			if timeDetail != nil {
				e.Ctx().GetSessionVars().SQLCPUUsages.MergeTikvCPUTime(timeDetail.ProcessTime)
			}
		}()
	}
	if e.RuntimeStats() != nil && e.snapshot != nil {
		e.snapshot.SetOption(kv.CollectRuntimeStats, nil)
	}
	if e.indexUsageReporter != nil {
		tableID := e.tblInfo.ID
		physicalTableID := GetPhysID(e.tblInfo, e.partitionDefIdx)
		kvReqTotal := e.stats.SnapshotRuntimeStats.GetCmdRPCCount(tikvrpc.CmdGet)
		rows := e.RuntimeStats().GetActRows()
		if e.idxInfo != nil {
			e.indexUsageReporter.ReportPointGetIndexUsage(tableID, physicalTableID, e.idxInfo.ID, kvReqTotal, rows)
		} else {
			e.indexUsageReporter.ReportPointGetIndexUsageForHandle(e.tblInfo, physicalTableID, kvReqTotal, rows)
		}
	}
	e.done = false
	return nil
}

// Next implements the Executor interface.
func (e *PointGetExecutor) Next(ctx context.Context, req *chunk.Chunk) error {
	req.Reset()
	if e.done {
		return nil
	}
	e.done = true

	var err error
	tblID := GetPhysID(e.tblInfo, e.partitionDefIdx)
	if e.lock {
		e.UpdateDeltaForTableID(tblID)
	}
	if e.idxInfo != nil {
		if isCommonHandleRead(e.tblInfo, e.idxInfo) {
			handleBytes, err := plannercore.EncodeUniqueIndexValuesForKey(e.Ctx(), e.tblInfo, e.idxInfo, e.idxVals)
			if err != nil {
				if kv.ErrNotExist.Equal(err) {
					return nil
				}
				return err
			}
			e.handle, err = kv.NewCommonHandle(handleBytes)
			if err != nil {
				return err
			}
		} else {
			e.idxKey, err = plannercore.EncodeUniqueIndexKey(e.Ctx(), e.tblInfo, e.idxInfo, e.idxVals, tblID)
			if err != nil && !kv.ErrNotExist.Equal(err) {
				return err
			}

			// lockNonExistIdxKey indicates the key will be locked regardless of its existence.
			lockNonExistIdxKey := !e.Ctx().GetSessionVars().IsPessimisticReadConsistency()
			// Non-exist keys are also locked if the isolation level is not read consistency,
			// lock it before read here, then it's able to read from pessimistic lock cache.
			if lockNonExistIdxKey {
				err = e.lockKeyIfNeeded(ctx, e.idxKey)
				if err != nil {
					return err
				}
				e.handleVal, err = e.get(ctx, e.idxKey)
				if err != nil {
					if !kv.ErrNotExist.Equal(err) {
						return err
					}
				}
			} else {
				if e.lock {
					e.handleVal, err = e.lockKeyIfExists(ctx, e.idxKey)
					if err != nil {
						return err
					}
				} else {
					e.handleVal, err = e.get(ctx, e.idxKey)
					if err != nil {
						if !kv.ErrNotExist.Equal(err) {
							return err
						}
					}
				}
			}

			if len(e.handleVal) == 0 {
				return nil
			}

			var iv kv.Handle
			iv, err = tablecodec.DecodeHandleInIndexValue(e.handleVal)
			if err != nil {
				return err
			}
			e.handle = iv

			// The injection is used to simulate following scenario:
			// 1. Session A create a point get query but pause before second time `GET` kv from backend
			// 2. Session B create an UPDATE query to update the record that will be obtained in step 1
			// 3. Then point get retrieve data from backend after step 2 finished
			// 4. Check the result
			failpoint.InjectContext(ctx, "pointGetRepeatableReadTest-step1", func() {
				if ch, ok := ctx.Value("pointGetRepeatableReadTest").(chan struct{}); ok {
					// Make `UPDATE` continue
					close(ch)
				}
				// Wait `UPDATE` finished
				failpoint.InjectContext(ctx, "pointGetRepeatableReadTest-step2", nil)
			})
			if e.idxInfo.Global {
				_, pid, err := codec.DecodeInt(tablecodec.SplitIndexValue(e.handleVal).PartitionID)
				if err != nil {
					return err
				}
				tblID = pid
				pi := e.tblInfo.GetPartitionInfo()
				if !matchPartitionNames(tblID, e.partitionNames, pi) {
					return nil
				}
				for _, id := range pi.IDsInDDLToIgnore() {
					if id == pid {
						return nil
					}
				}
			}
		}
	}

	key := tablecodec.EncodeRowKeyWithHandle(tblID, e.handle)
	val, err := e.getAndLock(ctx, key)
	if err != nil {
		return err
	}
	if len(val) == 0 {
		if e.idxInfo != nil && !isCommonHandleRead(e.tblInfo, e.idxInfo) &&
			!e.Ctx().GetSessionVars().StmtCtx.WeakConsistency {
			return (&consistency.Reporter{
				HandleEncode: func(kv.Handle) kv.Key {
					return key
				},
				IndexEncode: func(*consistency.RecordData) kv.Key {
					return e.idxKey
				},
				Tbl:             e.tblInfo,
				Idx:             e.idxInfo,
				EnableRedactLog: e.Ctx().GetSessionVars().EnableRedactLog,
				Storage:         e.Ctx().GetStore(),
			}).ReportLookupInconsistent(ctx,
				1, 0,
				[]kv.Handle{e.handle},
				[]kv.Handle{e.handle},
				[]consistency.RecordData{{}},
			)
		}
		return nil
	}

	sctx := e.BaseExecutor.Ctx()
	schema := e.Schema()
	err = DecodeRowValToChunk(sctx, schema, e.tblInfo, e.handle, val, req, e.rowDecoder)
	if err != nil {
		return err
	}

	err = fillRowChecksum(sctx, 0, 1, schema, e.tblInfo, [][]byte{val}, []kv.Handle{e.handle}, req, nil)
	if err != nil {
		return err
	}

	err = table.FillVirtualColumnValue(e.virtualColumnRetFieldTypes, e.virtualColumnIndex,
		schema.Columns, e.columns, sctx.GetExprCtx(), req)
	if err != nil {
		return err
	}
	return nil
}

func shouldFillRowChecksum(schema *expression.Schema) (int, bool) {
	for idx, col := range schema.Columns {
		if col.ID == model.ExtraRowChecksumID {
			return idx, true
		}
	}
	return 0, false
}

func fillRowChecksum(
	sctx sessionctx.Context,
	start, end int,
	schema *expression.Schema, tblInfo *model.TableInfo,
	values [][]byte, handles []kv.Handle,
	req *chunk.Chunk, buf []byte,
) error {
	checksumColumnIndex, ok := shouldFillRowChecksum(schema)
	if !ok {
		return nil
	}

	var handleColIDs []int64
	if tblInfo.PKIsHandle {
		colInfo := tblInfo.GetPkColInfo()
		handleColIDs = []int64{colInfo.ID}
	} else if tblInfo.IsCommonHandle {
		pkIdx := tables.FindPrimaryIndex(tblInfo)
		for _, col := range pkIdx.Columns {
			colInfo := tblInfo.Columns[col.Offset]
			handleColIDs = append(handleColIDs, colInfo.ID)
		}
	}

	columnFt := make(map[int64]*types.FieldType)
	for idx := range tblInfo.Columns {
		col := tblInfo.Columns[idx]
		columnFt[col.ID] = &col.FieldType
	}
	tz := sctx.GetSessionVars().TimeZone
	ft := []*types.FieldType{schema.Columns[checksumColumnIndex].GetType(sctx.GetExprCtx().GetEvalCtx())}
	checksumCols := chunk.NewChunkWithCapacity(ft, req.Capacity())
	for i := start; i < end; i++ {
		handle, val := handles[i], values[i]
		if !rowcodec.IsNewFormat(val) {
			checksumCols.AppendNull(0)
			continue
		}
		datums, err := tablecodec.DecodeRowWithMapNew(val, columnFt, tz, nil)
		if err != nil {
			return err
		}
		datums, err = tablecodec.DecodeHandleToDatumMap(handle, handleColIDs, columnFt, tz, datums)
		if err != nil {
			return err
		}
		for _, col := range tblInfo.Columns {
			// cannot found from the datums, which means the data is not stored, this
			// may happen after `add column` executed, filling with the default value.
			_, ok := datums[col.ID]
			if !ok {
				colInfo := getColInfoByID(tblInfo, col.ID)
				d, err := table.GetColOriginDefaultValue(sctx.GetExprCtx(), colInfo)
				if err != nil {
					return err
				}
				datums[col.ID] = d
			}
		}

		colData := make([]rowcodec.ColData, len(tblInfo.Columns))
		for idx, col := range tblInfo.Columns {
			d := datums[col.ID]
			data := rowcodec.ColData{
				ColumnInfo: col,
				Datum:      &d,
			}
			colData[idx] = data
		}
		row := rowcodec.RowData{
			Cols: colData,
			Data: buf,
		}
		if !sort.IsSorted(row) {
			sort.Sort(row)
		}
		checksum, err := row.Checksum(tz)
		if err != nil {
			return err
		}
		checksumCols.AppendString(0, strconv.FormatUint(uint64(checksum), 10))
	}
	req.SetCol(checksumColumnIndex, checksumCols.Column(0))
	return nil
}

func (e *PointGetExecutor) getAndLock(ctx context.Context, key kv.Key) (val []byte, err error) {
	if e.Ctx().GetSessionVars().IsPessimisticReadConsistency() {
		// Only Lock the existing keys in RC isolation.
		if e.lock {
			val, err = e.lockKeyIfExists(ctx, key)
			if err != nil {
				return nil, err
			}
		} else {
			val, err = e.get(ctx, key)
			if err != nil {
				if !kv.ErrNotExist.Equal(err) {
					return nil, err
				}
				return nil, nil
			}
		}
		return val, nil
	}
	// Lock the key before get in RR isolation, then get will get the value from the cache.
	err = e.lockKeyIfNeeded(ctx, key)
	if err != nil {
		return nil, err
	}
	val, err = e.get(ctx, key)
	if err != nil {
		if !kv.ErrNotExist.Equal(err) {
			return nil, err
		}
		return nil, nil
	}
	return val, nil
}

func (e *PointGetExecutor) lockKeyIfNeeded(ctx context.Context, key []byte) error {
	_, err := e.lockKeyBase(ctx, key, false)
	return err
}

// lockKeyIfExists locks the key if needed, but won't lock the key if it doesn't exis.
// Returns the value of the key if the key exist.
func (e *PointGetExecutor) lockKeyIfExists(ctx context.Context, key []byte) ([]byte, error) {
	return e.lockKeyBase(ctx, key, true)
}

func (e *PointGetExecutor) lockKeyBase(ctx context.Context,
	key []byte,
	lockOnlyIfExists bool) ([]byte, error) {
	if len(key) == 0 {
		return nil, nil
	}

	if e.lock {
		seVars := e.Ctx().GetSessionVars()
		lockCtx, err := newLockCtx(e.Ctx(), e.lockWaitTime, 1)
		if err != nil {
			return nil, err
		}
		lockCtx.LockOnlyIfExists = lockOnlyIfExists
		lockCtx.InitReturnValues(1)
		err = doLockKeys(ctx, e.Ctx(), lockCtx, key)
		if err != nil {
			return nil, err
		}
		lockCtx.IterateValuesNotLocked(func(k, v []byte) {
			seVars.TxnCtx.SetPessimisticLockCache(k, v)
		})
		if len(e.handleVal) > 0 {
			seVars.TxnCtx.SetPessimisticLockCache(e.idxKey, e.handleVal)
		}
		if lockOnlyIfExists {
			return e.getValueFromLockCtx(ctx, lockCtx, key)
		}
	}

	return nil, nil
}

func (e *PointGetExecutor) getValueFromLockCtx(ctx context.Context,
	lockCtx *kv.LockCtx,
	key []byte) ([]byte, error) {
	if val, ok := lockCtx.Values[string(key)]; ok {
		if val.Exists {
			return val.Value, nil
		} else if val.AlreadyLocked {
			val, err := e.get(ctx, key)
			if err != nil {
				if !kv.ErrNotExist.Equal(err) {
					return nil, err
				}
				return nil, nil
			}
			return val, nil
		}
	}

	return nil, nil
}

// get will first try to get from txn buffer, then check the pessimistic lock cache,
// then the store. Kv.ErrNotExist will be returned if key is not found
func (e *PointGetExecutor) get(ctx context.Context, key kv.Key) ([]byte, error) {
	if len(key) == 0 {
		return nil, kv.ErrNotExist
	}

	var (
		val []byte
		err error
	)

	if e.txn.Valid() && !e.txn.IsReadOnly() {
		// We cannot use txn.Get directly here because the snapshot in txn and the snapshot of e.snapshot may be
		// different for pessimistic transaction.
		val, err = e.txn.GetMemBuffer().Get(ctx, key)
		if err == nil {
			return val, err
		}
		if !kv.IsErrNotFound(err) {
			return nil, err
		}
		// key does not exist in mem buffer, check the lock cache
		if e.lock {
			var ok bool
			val, ok = e.Ctx().GetSessionVars().TxnCtx.GetKeyInPessimisticLockCache(key)
			if ok {
				return val, nil
			}
		}
		// fallthrough to snapshot get.
	}

	lock := e.tblInfo.Lock
	if lock != nil && (lock.Tp == pmodel.TableLockRead || lock.Tp == pmodel.TableLockReadOnly) {
		if e.Ctx().GetSessionVars().EnablePointGetCache {
			cacheDB := e.Ctx().GetStore().GetMemCache()
			val, err = cacheDB.UnionGet(ctx, e.tblInfo.ID, e.snapshot, key)
			if err != nil {
				return nil, err
			}
			return val, nil
		}
	}
	// if not read lock or table was unlock then snapshot get
	if e.Ctx().GetSessionVars().MaxExecutionTime > 0 {
		// if the query has max execution time set, we need to set the context deadline for the get request
		ctxWithTimeout, cancel := context.WithTimeout(ctx, time.Duration(e.Ctx().GetSessionVars().MaxExecutionTime)*time.Millisecond)
		defer cancel()
		return e.snapshot.Get(ctxWithTimeout, key)
	}
	return e.snapshot.Get(ctx, key)
}

func (e *PointGetExecutor) verifyTxnScope() error {
	if e.txnScope == "" || e.txnScope == kv.GlobalTxnScope {
		return nil
	}

	var partName string
	is := e.Ctx().GetInfoSchema().(infoschema.InfoSchema)
	tblInfo, _ := is.TableByID(context.Background(), e.tblInfo.ID)
	tblName := tblInfo.Meta().Name.String()
	tblID := GetPhysID(tblInfo.Meta(), e.partitionDefIdx)
	if tblID != tblInfo.Meta().ID {
		partName = tblInfo.Meta().GetPartitionInfo().Definitions[*e.partitionDefIdx].Name.String()
	}
	valid := distsql.VerifyTxnScope(e.txnScope, tblID, is)
	if valid {
		return nil
	}
	if len(partName) > 0 {
		return dbterror.ErrInvalidPlacementPolicyCheck.GenWithStackByArgs(
			fmt.Sprintf("table %v's partition %v can not be read by %v txn_scope", tblName, partName, e.txnScope))
	}
	return dbterror.ErrInvalidPlacementPolicyCheck.GenWithStackByArgs(
		fmt.Sprintf("table %v can not be read by %v txn_scope", tblName, e.txnScope))
}

// DecodeRowValToChunk decodes row value into chunk checking row format used.
func DecodeRowValToChunk(sctx sessionctx.Context, schema *expression.Schema, tblInfo *model.TableInfo,
	handle kv.Handle, rowVal []byte, chk *chunk.Chunk, rd *rowcodec.ChunkDecoder) error {
	if rowcodec.IsNewFormat(rowVal) {
		return rd.DecodeToChunk(rowVal, handle, chk)
	}
	return decodeOldRowValToChunk(sctx, schema, tblInfo, handle, rowVal, chk)
}

func decodeOldRowValToChunk(sctx sessionctx.Context, schema *expression.Schema, tblInfo *model.TableInfo, handle kv.Handle,
	rowVal []byte, chk *chunk.Chunk) error {
	pkCols := tables.TryGetCommonPkColumnIds(tblInfo)
	prefixColIDs := tables.PrimaryPrefixColumnIDs(tblInfo)
	colID2CutPos := make(map[int64]int, schema.Len())
	for _, col := range schema.Columns {
		if _, ok := colID2CutPos[col.ID]; !ok {
			colID2CutPos[col.ID] = len(colID2CutPos)
		}
	}
	cutVals, err := tablecodec.CutRowNew(rowVal, colID2CutPos)
	if err != nil {
		return err
	}
	if cutVals == nil {
		cutVals = make([][]byte, len(colID2CutPos))
	}
	decoder := codec.NewDecoder(chk, sctx.GetSessionVars().Location())
	for i, col := range schema.Columns {
		// fill the virtual column value after row calculation
		if col.VirtualExpr != nil {
			chk.AppendNull(i)
			continue
		}
		ok, err := tryDecodeFromHandle(tblInfo, i, col, handle, chk, decoder, pkCols, prefixColIDs)
		if err != nil {
			return err
		}
		if ok {
			continue
		}
		cutPos := colID2CutPos[col.ID]
		if len(cutVals[cutPos]) == 0 {
			colInfo := getColInfoByID(tblInfo, col.ID)
			d, err1 := table.GetColOriginDefaultValue(sctx.GetExprCtx(), colInfo)
			if err1 != nil {
				return err1
			}
			chk.AppendDatum(i, &d)
			continue
		}
		_, err = decoder.DecodeOne(cutVals[cutPos], i, col.RetType)
		if err != nil {
			return err
		}
	}
	return nil
}

func tryDecodeFromHandle(tblInfo *model.TableInfo, schemaColIdx int, col *expression.Column, handle kv.Handle, chk *chunk.Chunk,
	decoder *codec.Decoder, pkCols []int64, prefixColIDs []int64) (bool, error) {
	if tblInfo.PKIsHandle && mysql.HasPriKeyFlag(col.RetType.GetFlag()) {
		chk.AppendInt64(schemaColIdx, handle.IntValue())
		return true, nil
	}
	if col.ID == model.ExtraHandleID {
		chk.AppendInt64(schemaColIdx, handle.IntValue())
		return true, nil
	}
	if types.NeedRestoredData(col.RetType) {
		return false, nil
	}
	// Try to decode common handle.
	if mysql.HasPriKeyFlag(col.RetType.GetFlag()) {
		for i, hid := range pkCols {
			if col.ID == hid && notPKPrefixCol(hid, prefixColIDs) {
				_, err := decoder.DecodeOne(handle.EncodedCol(i), schemaColIdx, col.RetType)
				if err != nil {
					return false, errors.Trace(err)
				}
				return true, nil
			}
		}
	}
	return false, nil
}

func notPKPrefixCol(colID int64, prefixColIDs []int64) bool {
	for _, pCol := range prefixColIDs {
		if pCol == colID {
			return false
		}
	}
	return true
}

func getColInfoByID(tbl *model.TableInfo, colID int64) *model.ColumnInfo {
	for _, col := range tbl.Columns {
		if col.ID == colID {
			return col
		}
	}
	return nil
}

type runtimeStatsWithSnapshot struct {
	*txnsnapshot.SnapshotRuntimeStats
}

func (e *runtimeStatsWithSnapshot) String() string {
	if e.SnapshotRuntimeStats != nil {
		return e.SnapshotRuntimeStats.String()
	}
	return ""
}

// Clone implements the RuntimeStats interface.
func (e *runtimeStatsWithSnapshot) Clone() execdetails.RuntimeStats {
	newRs := &runtimeStatsWithSnapshot{}
	if e.SnapshotRuntimeStats != nil {
		snapshotStats := e.SnapshotRuntimeStats.Clone()
		newRs.SnapshotRuntimeStats = snapshotStats
	}
	return newRs
}

// Merge implements the RuntimeStats interface.
func (e *runtimeStatsWithSnapshot) Merge(other execdetails.RuntimeStats) {
	tmp, ok := other.(*runtimeStatsWithSnapshot)
	if !ok {
		return
	}
	if tmp.SnapshotRuntimeStats != nil {
		if e.SnapshotRuntimeStats == nil {
			snapshotStats := tmp.SnapshotRuntimeStats.Clone()
			e.SnapshotRuntimeStats = snapshotStats
			return
		}
		e.SnapshotRuntimeStats.Merge(tmp.SnapshotRuntimeStats)
	}
}

// Tp implements the RuntimeStats interface.
func (*runtimeStatsWithSnapshot) Tp() int {
	return execdetails.TpRuntimeStatsWithSnapshot
}