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144 lines
4.0 KiB
144 lines
4.0 KiB
// Copyright 2017 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 core
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import (
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"github.com/pingcap/parser/ast"
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"github.com/pingcap/tidb/expression"
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"github.com/pingcap/tidb/infoschema"
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"github.com/pingcap/tidb/types/parser_driver"
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"github.com/pingcap/tidb/util/logutil"
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"go.uber.org/zap"
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)
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// Cacheable checks whether the input ast is cacheable.
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// Handle "ignore_plan_cache()" hint
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// If there are multiple hints, only one will take effect
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func Cacheable(node ast.Node, is infoschema.InfoSchema) bool {
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_, isSelect := node.(*ast.SelectStmt)
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_, isUpdate := node.(*ast.UpdateStmt)
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_, isInsert := node.(*ast.InsertStmt)
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_, isDelete := node.(*ast.DeleteStmt)
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_, isUnion := node.(*ast.UnionStmt)
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if !(isSelect || isUpdate || isInsert || isDelete || isUnion) {
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return false
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}
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checker := cacheableChecker{
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cacheable: true,
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schema: is,
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}
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node.Accept(&checker)
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return checker.cacheable
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}
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// cacheableChecker checks whether a query's plan can be cached, querys that:
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// 1. have ExistsSubqueryExpr, or
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// 2. have VariableExpr
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//
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// will not be cached currently.
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// NOTE: we can add more rules in the future.
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type cacheableChecker struct {
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cacheable bool
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schema infoschema.InfoSchema
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}
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// Enter implements Visitor interface.
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func (checker *cacheableChecker) Enter(in ast.Node) (out ast.Node, skipChildren bool) {
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switch node := in.(type) {
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case *ast.SelectStmt:
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for _, hints := range node.TableHints {
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if hints.HintName.L == HintIgnorePlanCache {
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checker.cacheable = false
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return in, true
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}
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}
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case *ast.DeleteStmt:
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for _, hints := range node.TableHints {
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if hints.HintName.L == HintIgnorePlanCache {
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checker.cacheable = false
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return in, true
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}
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}
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case *ast.UpdateStmt:
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for _, hints := range node.TableHints {
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if hints.HintName.L == HintIgnorePlanCache {
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checker.cacheable = false
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return in, true
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}
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}
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case *ast.VariableExpr, *ast.ExistsSubqueryExpr, *ast.SubqueryExpr:
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checker.cacheable = false
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return in, true
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case *ast.FuncCallExpr:
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if _, found := expression.UnCacheableFunctions[node.FnName.L]; found {
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checker.cacheable = false
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return in, true
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}
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case *ast.OrderByClause:
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for _, item := range node.Items {
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if _, isParamMarker := item.Expr.(*driver.ParamMarkerExpr); isParamMarker {
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checker.cacheable = false
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return in, true
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}
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}
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case *ast.GroupByClause:
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for _, item := range node.Items {
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if _, isParamMarker := item.Expr.(*driver.ParamMarkerExpr); isParamMarker {
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checker.cacheable = false
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return in, true
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}
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}
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case *ast.Limit:
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if node.Count != nil {
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if _, isParamMarker := node.Count.(*driver.ParamMarkerExpr); isParamMarker {
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checker.cacheable = false
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return in, true
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}
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}
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if node.Offset != nil {
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if _, isParamMarker := node.Offset.(*driver.ParamMarkerExpr); isParamMarker {
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checker.cacheable = false
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return in, true
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}
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}
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case *ast.FrameBound:
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if _, ok := node.Expr.(*driver.ParamMarkerExpr); ok {
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checker.cacheable = false
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return in, true
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}
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case *ast.TableName:
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if checker.isPartitionTable(node) {
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checker.cacheable = false
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return in, true
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}
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}
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return in, false
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}
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func (checker *cacheableChecker) isPartitionTable(tn *ast.TableName) bool {
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tb, err := checker.schema.TableByName(tn.Schema, tn.Name)
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if err != nil {
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logutil.BgLogger().Error("Error occur in checking cacheable", zap.Error(err))
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return false
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}
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if tb.Meta().Partition != nil {
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return true
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}
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return false
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}
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// Leave implements Visitor interface.
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func (checker *cacheableChecker) Leave(in ast.Node) (out ast.Node, ok bool) {
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return in, checker.cacheable
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}
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