tidb plan_cache 源码
tidb plan_cache 代码
文件路径：/planner/core/plan_cache.go
// Copyright 2022 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 core
import (
"context"
"github.com/pingcap/errors"
"github.com/pingcap/tidb/bindinfo"
"github.com/pingcap/tidb/domain"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/infoschema"
"github.com/pingcap/tidb/kv"
"github.com/pingcap/tidb/metrics"
"github.com/pingcap/tidb/parser/ast"
"github.com/pingcap/tidb/parser/mysql"
"github.com/pingcap/tidb/privilege"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/sessionctx/stmtctx"
"github.com/pingcap/tidb/sessionctx/variable"
"github.com/pingcap/tidb/sessiontxn/staleread"
"github.com/pingcap/tidb/table/tables"
"github.com/pingcap/tidb/types"
driver "github.com/pingcap/tidb/types/parser_driver"
"github.com/pingcap/tidb/util/chunk"
"github.com/pingcap/tidb/util/collate"
"github.com/pingcap/tidb/util/kvcache"
"github.com/pingcap/tidb/util/logutil"
"github.com/pingcap/tidb/util/ranger"
"go.uber.org/zap"
)
func planCachePreprocess(sctx sessionctx.Context, isGeneralPlanCache bool, is infoschema.InfoSchema,
stmt *PlanCacheStmt, params []expression.Expression) error {
vars := sctx.GetSessionVars()
stmtAst := stmt.PreparedAst
vars.StmtCtx.StmtType = stmtAst.StmtType
// step 1: check parameter number
if len(stmtAst.Params) != len(params) {
return errors.Trace(ErrWrongParamCount)
}
// step 2: set parameter values
for i, usingParam := range params {
val, err := usingParam.Eval(chunk.Row{})
if err != nil {
return err
}
param := stmtAst.Params[i].(*driver.ParamMarkerExpr)
if isGetVarBinaryLiteral(sctx, usingParam) {
binVal, convErr := val.ToBytes()
if convErr != nil {
return convErr
}
val.SetBinaryLiteral(binVal)
}
param.Datum = val
param.InExecute = true
vars.PreparedParams = append(vars.PreparedParams, val)
}
// step 3: check schema version
if stmtAst.SchemaVersion != is.SchemaMetaVersion() {
// In order to avoid some correctness issues, we have to clear the
// cached plan once the schema version is changed.
// Cached plan in prepared struct does NOT have a "cache key" with
// schema version like prepared plan cache key
stmtAst.CachedPlan = nil
stmt.Executor = nil
stmt.ColumnInfos = nil
// If the schema version has changed we need to preprocess it again,
// if this time it failed, the real reason for the error is schema changed.
// Example:
// When running update in prepared statement's schema version distinguished from the one of execute statement
// We should reset the tableRefs in the prepared update statements, otherwise, the ast nodes still hold the old
// tableRefs columnInfo which will cause chaos in logic of trying point get plan. (should ban non-public column)
ret := &PreprocessorReturn{InfoSchema: is}
err := Preprocess(sctx, stmtAst.Stmt, InPrepare, WithPreprocessorReturn(ret))
if err != nil {
return ErrSchemaChanged.GenWithStack("Schema change caused error: %s", err.Error())
}
stmtAst.SchemaVersion = is.SchemaMetaVersion()
}
// step 4: handle expiration
// If the lastUpdateTime less than expiredTimeStamp4PC,
// it means other sessions have executed 'admin flush instance plan_cache'.
// So we need to clear the current session's plan cache.
// And update lastUpdateTime to the newest one.
expiredTimeStamp4PC := domain.GetDomain(sctx).ExpiredTimeStamp4PC()
if stmtAst.UseCache && expiredTimeStamp4PC.Compare(vars.LastUpdateTime4PC) > 0 {
sctx.GetPlanCache(isGeneralPlanCache).DeleteAll()
stmtAst.CachedPlan = nil
vars.LastUpdateTime4PC = expiredTimeStamp4PC
}
return nil
}
// GetPlanFromSessionPlanCache is the entry point of Plan Cache.
// It tries to get a valid cached plan from this session's plan cache.
// If there is no such a plan, it'll call the optimizer to generate a new one.
// isGeneralPlanCache indicates whether to use the general plan cache or the prepared plan cache.
func GetPlanFromSessionPlanCache(ctx context.Context, sctx sessionctx.Context,
isGeneralPlanCache bool, is infoschema.InfoSchema, stmt *PlanCacheStmt,
params []expression.Expression) (plan Plan, names []*types.FieldName, err error) {
if err := planCachePreprocess(sctx, isGeneralPlanCache, is, stmt, params); err != nil {
return nil, nil, err
}
var cacheKey kvcache.Key
sessVars := sctx.GetSessionVars()
stmtCtx := sessVars.StmtCtx
stmtAst := stmt.PreparedAst
stmtCtx.UseCache = stmtAst.UseCache
var bindSQL string
var ignorePlanCache = false
// In rc or for update read, we need the latest schema version to decide whether we need to
// rebuild the plan. So we set this value in rc or for update read. In other cases, let it be 0.
var latestSchemaVersion int64
if stmtAst.UseCache {
bindSQL, ignorePlanCache = GetBindSQL4PlanCache(sctx, stmt)
if sctx.GetSessionVars().IsIsolation(ast.ReadCommitted) || stmt.ForUpdateRead {
// In Rc or ForUpdateRead, we should check if the information schema has been changed since
// last time. If it changed, we should rebuild the plan. Here, we use a different and more
// up-to-date schema version which can lead plan cache miss and thus, the plan will be rebuilt.
latestSchemaVersion = domain.GetDomain(sctx).InfoSchema().SchemaMetaVersion()
}
if cacheKey, err = NewPlanCacheKey(sctx.GetSessionVars(), stmt.StmtText,
stmt.StmtDB, stmtAst.SchemaVersion, latestSchemaVersion, bindSQL); err != nil {
return nil, nil, err
}
}
paramNum, paramTypes := parseParamTypes(sctx, params)
if stmtAst.UseCache && stmtAst.CachedPlan != nil && !ignorePlanCache { // for point query plan
if plan, names, ok, err := getPointQueryPlan(stmtAst, sessVars, stmtCtx); ok {
return plan, names, err
}
}
if stmtAst.UseCache && !ignorePlanCache { // for general plans
if plan, names, ok, err := getGeneralPlan(sctx, isGeneralPlanCache, cacheKey, bindSQL, is, stmt,
paramTypes); err != nil || ok {
return plan, names, err
}
}
return generateNewPlan(ctx, sctx, isGeneralPlanCache, is, stmt, ignorePlanCache, cacheKey,
latestSchemaVersion, paramNum, paramTypes, bindSQL)
}
// parseParamTypes get parameters' types in PREPARE statement
func parseParamTypes(sctx sessionctx.Context, params []expression.Expression) (paramNum int, paramTypes []*types.FieldType) {
paramNum = len(params)
for _, param := range params {
if c, ok := param.(*expression.Constant); ok { // from binary protocol
paramTypes = append(paramTypes, c.GetType())
continue
}
// from text protocol, there must be a GetVar function
name := param.(*expression.ScalarFunction).GetArgs()[0].String()
tp, ok := sctx.GetSessionVars().GetUserVarType(name)
if !ok {
tp = types.NewFieldType(mysql.TypeNull)
}
paramTypes = append(paramTypes, tp)
}
return
}
func getPointQueryPlan(stmt *ast.Prepared, sessVars *variable.SessionVars, stmtCtx *stmtctx.StatementContext) (Plan,
[]*types.FieldName, bool, error) {
// short path for point-get plans
// Rewriting the expression in the select.where condition will convert its
// type from "paramMarker" to "Constant".When Point Select queries are executed,
// the expression in the where condition will not be evaluated,
// so you don't need to consider whether prepared.useCache is enabled.
plan := stmt.CachedPlan.(Plan)
names := stmt.CachedNames.(types.NameSlice)
err := RebuildPlan4CachedPlan(plan)
if err != nil {
logutil.BgLogger().Debug("rebuild range failed", zap.Error(err))
return nil, nil, false, nil
}
if metrics.ResettablePlanCacheCounterFortTest {
metrics.PlanCacheCounter.WithLabelValues("prepare").Inc()
} else {
planCacheCounter.Inc()
}
sessVars.FoundInPlanCache = true
stmtCtx.PointExec = true
return plan, names, true, nil
}
func getGeneralPlan(sctx sessionctx.Context, isGeneralPlanCache bool, cacheKey kvcache.Key, bindSQL string,
is infoschema.InfoSchema, stmt *PlanCacheStmt, paramTypes []*types.FieldType) (Plan,
[]*types.FieldName, bool, error) {
sessVars := sctx.GetSessionVars()
stmtCtx := sessVars.StmtCtx
candidate, exist := sctx.GetPlanCache(isGeneralPlanCache).Get(cacheKey, paramTypes)
if !exist {
return nil, nil, false, nil
}
cachedVal := candidate.(*PlanCacheValue)
if err := CheckPreparedPriv(sctx, stmt, is); err != nil {
return nil, nil, false, err
}
for tblInfo, unionScan := range cachedVal.TblInfo2UnionScan {
if !unionScan && tableHasDirtyContent(sctx, tblInfo) {
// TODO we can inject UnionScan into cached plan to avoid invalidating it, though
// rebuilding the filters in UnionScan is pretty trivial.
sctx.GetPlanCache(isGeneralPlanCache).Delete(cacheKey)
return nil, nil, false, nil
}
}
err := RebuildPlan4CachedPlan(cachedVal.Plan)
if err != nil {
logutil.BgLogger().Debug("rebuild range failed", zap.Error(err))
return nil, nil, false, nil
}
sessVars.FoundInPlanCache = true
if len(bindSQL) > 0 {
// When the `len(bindSQL) > 0`, it means we use the binding.
// So we need to record this.
sessVars.FoundInBinding = true
}
if metrics.ResettablePlanCacheCounterFortTest {
metrics.PlanCacheCounter.WithLabelValues("prepare").Inc()
} else {
planCacheCounter.Inc()
}
stmtCtx.SetPlanDigest(stmt.NormalizedPlan, stmt.PlanDigest)
return cachedVal.Plan, cachedVal.OutPutNames, true, nil
}
// generateNewPlan call the optimizer to generate a new plan for current statement
// and try to add it to cache
func generateNewPlan(ctx context.Context, sctx sessionctx.Context, isGeneralPlanCache bool, is infoschema.InfoSchema, stmt *PlanCacheStmt,
ignorePlanCache bool, cacheKey kvcache.Key, latestSchemaVersion int64, paramNum int,
paramTypes []*types.FieldType, bindSQL string) (Plan, []*types.FieldName, error) {
stmtAst := stmt.PreparedAst
sessVars := sctx.GetSessionVars()
stmtCtx := sessVars.StmtCtx
planCacheMissCounter.Inc()
sctx.GetSessionVars().StmtCtx.InPreparedPlanBuilding = true
p, names, err := OptimizeAstNode(ctx, sctx, stmtAst.Stmt, is)
sctx.GetSessionVars().StmtCtx.InPreparedPlanBuilding = false
if err != nil {
return nil, nil, err
}
err = tryCachePointPlan(ctx, sctx, stmt, is, p)
if err != nil {
return nil, nil, err
}
// We only cache the tableDual plan when the number of parameters are zero.
if containTableDual(p) && paramNum > 0 {
stmtCtx.SkipPlanCache = true
}
if stmtAst.UseCache && !stmtCtx.SkipPlanCache && !ignorePlanCache {
// rebuild key to exclude kv.TiFlash when stmt is not read only
if _, isolationReadContainTiFlash := sessVars.IsolationReadEngines[kv.TiFlash]; isolationReadContainTiFlash && !IsReadOnly(stmtAst.Stmt, sessVars) {
delete(sessVars.IsolationReadEngines, kv.TiFlash)
if cacheKey, err = NewPlanCacheKey(sessVars, stmt.StmtText, stmt.StmtDB,
stmtAst.SchemaVersion, latestSchemaVersion, bindSQL); err != nil {
return nil, nil, err
}
sessVars.IsolationReadEngines[kv.TiFlash] = struct{}{}
}
cached := NewPlanCacheValue(p, names, stmtCtx.TblInfo2UnionScan, paramTypes)
stmt.NormalizedPlan, stmt.PlanDigest = NormalizePlan(p)
stmtCtx.SetPlan(p)
stmtCtx.SetPlanDigest(stmt.NormalizedPlan, stmt.PlanDigest)
sctx.GetPlanCache(isGeneralPlanCache).Put(cacheKey, cached, paramTypes)
}
sessVars.FoundInPlanCache = false
return p, names, err
}
// RebuildPlan4CachedPlan will rebuild this plan under current user parameters.
func RebuildPlan4CachedPlan(p Plan) error {
sc := p.SCtx().GetSessionVars().StmtCtx
sc.InPreparedPlanBuilding = true
defer func() { sc.InPreparedPlanBuilding = false }()
return rebuildRange(p)
}
// rebuildRange doesn't set mem limit for building ranges. There are two reasons why we don't restrict range mem usage here.
// 1. The cached plan must be able to build complete ranges under mem limit when it is generated. Hence we can just build
// ranges from x.AccessConditions. The only difference between the last ranges and new ranges is the change of parameter
// values, which doesn't cause much change on the mem usage of complete ranges.
// 2. Different parameter values can change the mem usage of complete ranges. If we set range mem limit here, range fallback
// may heppen and cause correctness problem. For example, a in (?, ?, ?) is the access condition. When the plan is firstly
// generated, its complete ranges are ['a','a'], ['b','b'], ['c','c'], whose mem usage is under range mem limit 100B.
// When the cached plan is hit, the complete ranges may become ['aaa','aaa'], ['bbb','bbb'], ['ccc','ccc'], whose mem
// usage exceeds range mem limit 100B, and range fallback happens and tidb may fetch more rows than users expect.
func rebuildRange(p Plan) error {
sctx := p.SCtx()
sc := p.SCtx().GetSessionVars().StmtCtx
var err error
switch x := p.(type) {
case *PhysicalIndexHashJoin:
return rebuildRange(&x.PhysicalIndexJoin)
case *PhysicalIndexMergeJoin:
return rebuildRange(&x.PhysicalIndexJoin)
case *PhysicalIndexJoin:
if err := x.Ranges.Rebuild(); err != nil {
return err
}
for _, child := range x.Children() {
err = rebuildRange(child)
if err != nil {
return err
}
}
case *PhysicalTableScan:
err = buildRangeForTableScan(sctx, x)
if err != nil {
return err
}
case *PhysicalIndexScan:
err = buildRangeForIndexScan(sctx, x)
if err != nil {
return err
}
case *PhysicalTableReader:
err = rebuildRange(x.TablePlans[0])
if err != nil {
return err
}
case *PhysicalIndexReader:
err = rebuildRange(x.IndexPlans[0])
if err != nil {
return err
}
case *PhysicalIndexLookUpReader:
err = rebuildRange(x.IndexPlans[0])
if err != nil {
return err
}
case *PointGetPlan:
// if access condition is not nil, which means it's a point get generated by cbo.
if x.AccessConditions != nil {
if x.IndexInfo != nil {
ranges, err := ranger.DetachCondAndBuildRangeForIndex(x.ctx, x.AccessConditions, x.IdxCols, x.IdxColLens)
if err != nil {
return err
}
if len(ranges.Ranges) == 0 || len(ranges.AccessConds) != len(x.AccessConditions) {
return errors.New("failed to rebuild range: the length of the range has changed")
}
for i := range x.IndexValues {
x.IndexValues[i] = ranges.Ranges[0].LowVal[i]
}
} else {
var pkCol *expression.Column
if x.TblInfo.PKIsHandle {
if pkColInfo := x.TblInfo.GetPkColInfo(); pkColInfo != nil {
pkCol = expression.ColInfo2Col(x.schema.Columns, pkColInfo)
}
}
if pkCol != nil {
ranges, _, _, err := ranger.BuildTableRange(x.AccessConditions, x.ctx, pkCol.RetType, 0)
if err != nil {
return err
}
if len(ranges) == 0 {
return errors.New("failed to rebuild range: the length of the range has changed")
}
x.Handle = kv.IntHandle(ranges[0].LowVal[0].GetInt64())
}
}
}
// The code should never run here as long as we're not using point get for partition table.
// And if we change the logic one day, here work as defensive programming to cache the error.
if x.PartitionInfo != nil {
// TODO: relocate the partition after rebuilding range to make PlanCache support PointGet
return errors.New("point get for partition table can not use plan cache")
}
if x.HandleConstant != nil {
dVal, err := convertConstant2Datum(sc, x.HandleConstant, x.handleFieldType)
if err != nil {
return err
}
iv, err := dVal.ToInt64(sc)
if err != nil {
return err
}
x.Handle = kv.IntHandle(iv)
return nil
}
for i, param := range x.IndexConstants {
if param != nil {
dVal, err := convertConstant2Datum(sc, param, x.ColsFieldType[i])
if err != nil {
return err
}
x.IndexValues[i] = *dVal
}
}
return nil
case *BatchPointGetPlan:
// if access condition is not nil, which means it's a point get generated by cbo.
if x.AccessConditions != nil {
if x.IndexInfo != nil {
ranges, err := ranger.DetachCondAndBuildRangeForIndex(x.ctx, x.AccessConditions, x.IdxCols, x.IdxColLens)
if err != nil {
return err
}
if len(ranges.Ranges) != len(x.IndexValues) || len(ranges.AccessConds) != len(x.AccessConditions) {
return errors.New("failed to rebuild range: the length of the range has changed")
}
for i := range x.IndexValues {
copy(x.IndexValues[i], ranges.Ranges[i].LowVal)
}
} else {
var pkCol *expression.Column
if x.TblInfo.PKIsHandle {
if pkColInfo := x.TblInfo.GetPkColInfo(); pkColInfo != nil {
pkCol = expression.ColInfo2Col(x.schema.Columns, pkColInfo)
}
}
if pkCol != nil {
ranges, _, _, err := ranger.BuildTableRange(x.AccessConditions, x.ctx, pkCol.RetType, 0)
if err != nil {
return err
}
if len(ranges) != len(x.Handles) {
return errors.New("failed to rebuild range: the length of the range has changed")
}
for i := range ranges {
x.Handles[i] = kv.IntHandle(ranges[i].LowVal[0].GetInt64())
}
}
}
}
for i, param := range x.HandleParams {
if param != nil {
dVal, err := convertConstant2Datum(sc, param, x.HandleType)
if err != nil {
return err
}
iv, err := dVal.ToInt64(sc)
if err != nil {
return err
}
x.Handles[i] = kv.IntHandle(iv)
}
}
for i, params := range x.IndexValueParams {
if len(params) < 1 {
continue
}
for j, param := range params {
if param != nil {
dVal, err := convertConstant2Datum(sc, param, x.IndexColTypes[j])
if err != nil {
return err
}
x.IndexValues[i][j] = *dVal
}
}
}
case *PhysicalIndexMergeReader:
indexMerge := p.(*PhysicalIndexMergeReader)
for _, partialPlans := range indexMerge.PartialPlans {
err = rebuildRange(partialPlans[0])
if err != nil {
return err
}
}
// We don't need to handle the indexMerge.TablePlans, because the tablePlans
// only can be (Selection) + TableRowIDScan. There have no range need to rebuild.
case PhysicalPlan:
for _, child := range x.Children() {
err = rebuildRange(child)
if err != nil {
return err
}
}
case *Insert:
if x.SelectPlan != nil {
return rebuildRange(x.SelectPlan)
}
case *Update:
if x.SelectPlan != nil {
return rebuildRange(x.SelectPlan)
}
case *Delete:
if x.SelectPlan != nil {
return rebuildRange(x.SelectPlan)
}
}
return nil
}
func convertConstant2Datum(sc *stmtctx.StatementContext, con *expression.Constant, target *types.FieldType) (*types.Datum, error) {
val, err := con.Eval(chunk.Row{})
if err != nil {
return nil, err
}
dVal, err := val.ConvertTo(sc, target)
if err != nil {
return nil, err
}
// The converted result must be same as original datum.
cmp, err := dVal.Compare(sc, &val, collate.GetCollator(target.GetCollate()))
if err != nil || cmp != 0 {
return nil, errors.New("Convert constant to datum is failed, because the constant has changed after the covert")
}
return &dVal, nil
}
func buildRangeForTableScan(sctx sessionctx.Context, ts *PhysicalTableScan) (err error) {
if ts.Table.IsCommonHandle {
pk := tables.FindPrimaryIndex(ts.Table)
pkCols := make([]*expression.Column, 0, len(pk.Columns))
pkColsLen := make([]int, 0, len(pk.Columns))
for _, colInfo := range pk.Columns {
if pkCol := expression.ColInfo2Col(ts.schema.Columns, ts.Table.Columns[colInfo.Offset]); pkCol != nil {
pkCols = append(pkCols, pkCol)
// We need to consider the prefix index.
// For example: when we have 'a varchar(50), index idx(a(10))'
// So we will get 'colInfo.Length = 50' and 'pkCol.RetType.flen = 10'.
// In 'hasPrefix' function from 'util/ranger/ranger.go' file,
// we use 'columnLength == types.UnspecifiedLength' to check whether we have prefix index.
if colInfo.Length != types.UnspecifiedLength && colInfo.Length == pkCol.RetType.GetFlen() {
pkColsLen = append(pkColsLen, types.UnspecifiedLength)
} else {
pkColsLen = append(pkColsLen, colInfo.Length)
}
}
}
if len(pkCols) > 0 {
res, err := ranger.DetachCondAndBuildRangeForIndex(sctx, ts.AccessCondition, pkCols, pkColsLen)
if err != nil {
return err
}
if len(res.AccessConds) != len(ts.AccessCondition) {
return errors.New("rebuild range for cached plan failed")
}
ts.Ranges = res.Ranges
} else {
ts.Ranges = ranger.FullRange()
}
} else {
var pkCol *expression.Column
if ts.Table.PKIsHandle {
if pkColInfo := ts.Table.GetPkColInfo(); pkColInfo != nil {
pkCol = expression.ColInfo2Col(ts.schema.Columns, pkColInfo)
}
}
if pkCol != nil {
ts.Ranges, _, _, err = ranger.BuildTableRange(ts.AccessCondition, sctx, pkCol.RetType, 0)
if err != nil {
return err
}
} else {
ts.Ranges = ranger.FullIntRange(false)
}
}
return
}
func buildRangeForIndexScan(sctx sessionctx.Context, is *PhysicalIndexScan) (err error) {
if len(is.IdxCols) == 0 {
is.Ranges = ranger.FullRange()
return
}
res, err := ranger.DetachCondAndBuildRangeForIndex(sctx, is.AccessCondition, is.IdxCols, is.IdxColLens)
if err != nil {
return err
}
if len(res.AccessConds) != len(is.AccessCondition) {
return errors.New("rebuild range for cached plan failed")
}
is.Ranges = res.Ranges
return
}
// CheckPreparedPriv checks the privilege of the prepared statement
func CheckPreparedPriv(sctx sessionctx.Context, stmt *PlanCacheStmt, is infoschema.InfoSchema) error {
if pm := privilege.GetPrivilegeManager(sctx); pm != nil {
visitInfo := VisitInfo4PrivCheck(is, stmt.PreparedAst.Stmt, stmt.VisitInfos)
if err := CheckPrivilege(sctx.GetSessionVars().ActiveRoles, pm, visitInfo); err != nil {
return err
}
}
err := CheckTableLock(sctx, is, stmt.VisitInfos)
return err
}
// tryCachePointPlan will try to cache point execution plan, there may be some
// short paths for these executions, currently "point select" and "point update"
func tryCachePointPlan(_ context.Context, sctx sessionctx.Context,
stmt *PlanCacheStmt, _ infoschema.InfoSchema, p Plan) error {
if !sctx.GetSessionVars().StmtCtx.UseCache || sctx.GetSessionVars().StmtCtx.SkipPlanCache {
return nil
}
var (
stmtAst = stmt.PreparedAst
ok bool
err error
names types.NameSlice
)
if _, _ok := p.(*PointGetPlan); _ok {
ok, err = IsPointGetWithPKOrUniqueKeyByAutoCommit(sctx, p)
names = p.OutputNames()
if err != nil {
return err
}
}
if ok {
// just cache point plan now
stmtAst.CachedPlan = p
stmtAst.CachedNames = names
stmt.NormalizedPlan, stmt.PlanDigest = NormalizePlan(p)
sctx.GetSessionVars().StmtCtx.SetPlan(p)
sctx.GetSessionVars().StmtCtx.SetPlanDigest(stmt.NormalizedPlan, stmt.PlanDigest)
}
return err
}
func containTableDual(p Plan) bool {
_, isTableDual := p.(*PhysicalTableDual)
if isTableDual {
return true
}
physicalPlan, ok := p.(PhysicalPlan)
if !ok {
return false
}
childContainTableDual := false
for _, child := range physicalPlan.Children() {
childContainTableDual = childContainTableDual || containTableDual(child)
}
return childContainTableDual
}
// GetBindSQL4PlanCache used to get the bindSQL for plan cache to build the plan cache key.
func GetBindSQL4PlanCache(sctx sessionctx.Context, stmt *PlanCacheStmt) (string, bool) {
useBinding := sctx.GetSessionVars().UsePlanBaselines
ignore := false
if !useBinding || stmt.PreparedAst.Stmt == nil || stmt.NormalizedSQL4PC == "" || stmt.SQLDigest4PC == "" {
return "", ignore
}
if sctx.Value(bindinfo.SessionBindInfoKeyType) == nil {
return "", ignore
}
sessionHandle := sctx.Value(bindinfo.SessionBindInfoKeyType).(*bindinfo.SessionHandle)
bindRecord := sessionHandle.GetBindRecord(stmt.SQLDigest4PC, stmt.NormalizedSQL4PC, "")
if bindRecord != nil {
enabledBinding := bindRecord.FindEnabledBinding()
if enabledBinding != nil {
ignore = enabledBinding.Hint.ContainTableHint(HintIgnorePlanCache)
return enabledBinding.BindSQL, ignore
}
}
globalHandle := domain.GetDomain(sctx).BindHandle()
if globalHandle == nil {
return "", ignore
}
bindRecord = globalHandle.GetBindRecord(stmt.SQLDigest4PC, stmt.NormalizedSQL4PC, "")
if bindRecord != nil {
enabledBinding := bindRecord.FindEnabledBinding()
if enabledBinding != nil {
ignore = enabledBinding.Hint.ContainTableHint(HintIgnorePlanCache)
return enabledBinding.BindSQL, ignore
}
}
return "", ignore
}
// IsPointPlanShortPathOK check if we can execute using plan cached in prepared structure
// Be careful with the short path, current precondition is ths cached plan satisfying
// IsPointGetWithPKOrUniqueKeyByAutoCommit
func IsPointPlanShortPathOK(sctx sessionctx.Context, is infoschema.InfoSchema, stmt *PlanCacheStmt) (bool, error) {
stmtAst := stmt.PreparedAst
if stmtAst.CachedPlan == nil || staleread.IsStmtStaleness(sctx) {
return false, nil
}
// check auto commit
if !IsAutoCommitTxn(sctx) {
return false, nil
}
if stmtAst.SchemaVersion != is.SchemaMetaVersion() {
stmtAst.CachedPlan = nil
stmt.ColumnInfos = nil
return false, nil
}
// maybe we'd better check cached plan type here, current
// only point select/update will be cached, see "getPhysicalPlan" func
var ok bool
var err error
switch stmtAst.CachedPlan.(type) {
case *PointGetPlan:
ok = true
case *Update:
pointUpdate := stmtAst.CachedPlan.(*Update)
_, ok = pointUpdate.SelectPlan.(*PointGetPlan)
if !ok {
err = errors.Errorf("cached update plan not point update")
stmtAst.CachedPlan = nil
return false, err
}
default:
ok = false
}
return ok, err
}
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