113 lines
2.9 KiB
Go
113 lines
2.9 KiB
Go
// Copyright 2015 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 optimizer
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import (
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"strings"
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"github.com/juju/errors"
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"github.com/pingcap/tidb/ast"
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"github.com/pingcap/tidb/context"
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"github.com/pingcap/tidb/infoschema"
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"github.com/pingcap/tidb/optimizer/plan"
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)
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// Optimize do optimization and create a Plan.
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// InfoSchema has to be passed in as parameter because
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// it can not be changed after resolving name.
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func Optimize(is infoschema.InfoSchema, ctx context.Context, node ast.Node) (plan.Plan, error) {
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if err := validate(node); err != nil {
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return nil, errors.Trace(err)
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}
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ast.SetFlag(node)
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if err := ResolveName(node, is, ctx); err != nil {
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return nil, errors.Trace(err)
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}
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if err := inferType(node); err != nil {
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return nil, errors.Trace(err)
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}
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if err := preEvaluate(ctx, node); err != nil {
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return nil, errors.Trace(err)
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}
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p, err := plan.BuildPlan(node)
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if err != nil {
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return nil, errors.Trace(err)
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}
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bestCost := plan.EstimateCost(p)
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bestPlan := p
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alts, err := plan.Alternatives(p)
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if err != nil {
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return nil, errors.Trace(err)
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}
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for _, alt := range alts {
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cost := plan.EstimateCost(alt)
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if cost < bestCost {
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bestCost = cost
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bestPlan = alt
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}
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}
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return bestPlan, nil
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}
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type supportChecker struct {
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unsupported bool
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}
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func (c *supportChecker) Enter(in ast.Node) (ast.Node, bool) {
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switch in.(type) {
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case *ast.SubqueryExpr, *ast.AggregateFuncExpr, *ast.GroupByClause, *ast.HavingClause, *ast.ParamMarkerExpr:
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c.unsupported = true
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case *ast.Join:
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x := in.(*ast.Join)
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if x.Right != nil {
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c.unsupported = true
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} else {
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ts, tsok := x.Left.(*ast.TableSource)
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if !tsok {
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c.unsupported = true
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} else {
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tn, tnok := ts.Source.(*ast.TableName)
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if !tnok {
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c.unsupported = true
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} else if strings.EqualFold(tn.Schema.O, infoschema.Name) {
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c.unsupported = true
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}
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}
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}
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case *ast.SelectStmt:
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x := in.(*ast.SelectStmt)
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if x.Distinct {
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c.unsupported = true
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}
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}
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return in, c.unsupported
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}
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func (c *supportChecker) Leave(in ast.Node) (ast.Node, bool) {
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return in, !c.unsupported
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}
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// IsSupported checks if the node is supported to use new plan.
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// We first support single table select statement without group by clause or aggregate functions.
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// TODO: 1. insert/update/delete. 2. join tables. 3. subquery. 4. group by and aggregate function.
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func IsSupported(node ast.Node) bool {
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if _, ok := node.(*ast.SelectStmt); !ok {
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return false
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}
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var checker supportChecker
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node.Accept(&checker)
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return !checker.unsupported
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}
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