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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 core
import (
"github.com/pingcap/parser/ast"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/infoschema"
"github.com/pingcap/tidb/types/parser_driver"
"github.com/pingcap/tidb/util/logutil"
"go.uber.org/zap"
)
// Cacheable checks whether the input ast is cacheable.
// Handle "ignore_plan_cache()" hint
// If there are multiple hints, only one will take effect
func Cacheable(node ast.Node, is infoschema.InfoSchema) bool {
_, isSelect := node.(*ast.SelectStmt)
_, isUpdate := node.(*ast.UpdateStmt)
_, isInsert := node.(*ast.InsertStmt)
_, isDelete := node.(*ast.DeleteStmt)
_, isUnion := node.(*ast.UnionStmt)
if !(isSelect || isUpdate || isInsert || isDelete || isUnion) {
return false
}
checker := cacheableChecker{
cacheable: true,
schema: is,
}
node.Accept(&checker)
return checker.cacheable
}
// cacheableChecker checks whether a query's plan can be cached, querys that:
// 1. have ExistsSubqueryExpr, or
// 2. have VariableExpr
//
// will not be cached currently.
// NOTE: we can add more rules in the future.
type cacheableChecker struct {
cacheable bool
schema infoschema.InfoSchema
}
// Enter implements Visitor interface.
func (checker *cacheableChecker) Enter(in ast.Node) (out ast.Node, skipChildren bool) {
switch node := in.(type) {
case *ast.SelectStmt:
for _, hints := range node.TableHints {
if hints.HintName.L == HintIgnorePlanCache {
checker.cacheable = false
return in, true
}
}
case *ast.DeleteStmt:
for _, hints := range node.TableHints {
if hints.HintName.L == HintIgnorePlanCache {
checker.cacheable = false
return in, true
}
}
case *ast.UpdateStmt:
for _, hints := range node.TableHints {
if hints.HintName.L == HintIgnorePlanCache {
checker.cacheable = false
return in, true
}
}
case *ast.VariableExpr, *ast.ExistsSubqueryExpr, *ast.SubqueryExpr:
checker.cacheable = false
return in, true
case *ast.FuncCallExpr:
if _, found := expression.UnCacheableFunctions[node.FnName.L]; found {
checker.cacheable = false
return in, true
}
case *ast.OrderByClause:
for _, item := range node.Items {
if _, isParamMarker := item.Expr.(*driver.ParamMarkerExpr); isParamMarker {
checker.cacheable = false
return in, true
}
}
case *ast.GroupByClause:
for _, item := range node.Items {
if _, isParamMarker := item.Expr.(*driver.ParamMarkerExpr); isParamMarker {
checker.cacheable = false
return in, true
}
}
case *ast.Limit:
if node.Count != nil {
if _, isParamMarker := node.Count.(*driver.ParamMarkerExpr); isParamMarker {
checker.cacheable = false
return in, true
}
}
if node.Offset != nil {
if _, isParamMarker := node.Offset.(*driver.ParamMarkerExpr); isParamMarker {
checker.cacheable = false
return in, true
}
}
case *ast.FrameBound:
if _, ok := node.Expr.(*driver.ParamMarkerExpr); ok {
checker.cacheable = false
return in, true
}
case *ast.TableName:
if checker.isPartitionTable(node) {
checker.cacheable = false
return in, true
}
}
return in, false
}
func (checker *cacheableChecker) isPartitionTable(tn *ast.TableName) bool {
tb, err := checker.schema.TableByName(tn.Schema, tn.Name)
if err != nil {
logutil.BgLogger().Error("Error occur in checking cacheable", zap.Error(err))
return false
}
if tb.Meta().Partition != nil {
return true
}
return false
}
// Leave implements Visitor interface.
func (checker *cacheableChecker) Leave(in ast.Node) (out ast.Node, ok bool) {
return in, checker.cacheable
}