gitroast/vendor/github.com/pingcap/tidb/optimizer/plan/refiner.go

194 lines
4.6 KiB
Go
Raw Normal View History

// Copyright 2015 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 plan
import (
"math"
"github.com/pingcap/tidb/ast"
"github.com/pingcap/tidb/model"
"github.com/pingcap/tidb/parser/opcode"
"github.com/pingcap/tidb/util/types"
)
// Refine tries to build index or table range.
func Refine(p Plan) error {
r := refiner{}
p.Accept(&r)
return r.err
}
type refiner struct {
err error
}
func (r *refiner) Enter(in Plan) (Plan, bool) {
return in, false
}
func (r *refiner) Leave(in Plan) (Plan, bool) {
switch x := in.(type) {
case *IndexScan:
r.buildIndexRange(x)
case *Limit:
x.SetLimit(0)
case *TableScan:
r.buildTableRange(x)
}
return in, r.err == nil
}
var fullRange = []rangePoint{
{start: true},
{value: types.MaxValueDatum()},
}
func (r *refiner) buildIndexRange(p *IndexScan) {
rb := rangeBuilder{}
if p.AccessEqualCount > 0 {
// Build ranges for equal access conditions.
point := rb.build(p.AccessConditions[0])
p.Ranges = rb.buildIndexRanges(point)
for i := 1; i < p.AccessEqualCount; i++ {
point = rb.build(p.AccessConditions[i])
p.Ranges = rb.appendIndexRanges(p.Ranges, point)
}
}
rangePoints := fullRange
// Build rangePoints for non-equal access condtions.
for i := p.AccessEqualCount; i < len(p.AccessConditions); i++ {
rangePoints = rb.intersection(rangePoints, rb.build(p.AccessConditions[i]))
}
if p.AccessEqualCount == 0 {
p.Ranges = rb.buildIndexRanges(rangePoints)
} else if p.AccessEqualCount < len(p.AccessConditions) {
p.Ranges = rb.appendIndexRanges(p.Ranges, rangePoints)
}
r.err = rb.err
return
}
func (r *refiner) buildTableRange(p *TableScan) {
if len(p.AccessConditions) == 0 {
p.Ranges = []TableRange{{math.MinInt64, math.MaxInt64}}
return
}
rb := rangeBuilder{}
rangePoints := fullRange
for _, cond := range p.AccessConditions {
rangePoints = rb.intersection(rangePoints, rb.build(cond))
}
p.Ranges = rb.buildTableRanges(rangePoints)
r.err = rb.err
}
// conditionChecker checks if this condition can be pushed to index plan.
type conditionChecker struct {
tableName model.CIStr
idx *model.IndexInfo
// the offset of the indexed column to be checked.
columnOffset int
pkName model.CIStr
}
func (c *conditionChecker) check(condition ast.ExprNode) bool {
switch x := condition.(type) {
case *ast.BinaryOperationExpr:
return c.checkBinaryOperation(x)
case *ast.BetweenExpr:
if ast.IsPreEvaluable(x.Left) && ast.IsPreEvaluable(x.Right) && c.checkColumnExpr(x.Expr) {
return true
}
case *ast.ColumnNameExpr:
return c.checkColumnExpr(x)
case *ast.IsNullExpr:
if c.checkColumnExpr(x.Expr) {
return true
}
case *ast.IsTruthExpr:
if c.checkColumnExpr(x.Expr) {
return true
}
case *ast.ParenthesesExpr:
return c.check(x.Expr)
case *ast.PatternInExpr:
if x.Sel != nil || x.Not {
return false
}
if !c.checkColumnExpr(x.Expr) {
return false
}
for _, val := range x.List {
if !ast.IsPreEvaluable(val) {
return false
}
}
return true
case *ast.PatternLikeExpr:
if x.Not {
return false
}
if !c.checkColumnExpr(x.Expr) {
return false
}
if !ast.IsPreEvaluable(x.Pattern) {
return false
}
patternVal := x.Pattern.GetValue()
if patternVal == nil {
return false
}
patternStr, err := types.ToString(patternVal)
if err != nil {
return false
}
firstChar := patternStr[0]
return firstChar != '%' && firstChar != '.'
}
return false
}
func (c *conditionChecker) checkBinaryOperation(b *ast.BinaryOperationExpr) bool {
switch b.Op {
case opcode.OrOr:
return c.check(b.L) && c.check(b.R)
case opcode.AndAnd:
return c.check(b.L) && c.check(b.R)
case opcode.EQ, opcode.NE, opcode.GE, opcode.GT, opcode.LE, opcode.LT:
if ast.IsPreEvaluable(b.L) {
return c.checkColumnExpr(b.R)
} else if ast.IsPreEvaluable(b.R) {
return c.checkColumnExpr(b.L)
}
}
return false
}
func (c *conditionChecker) checkColumnExpr(expr ast.ExprNode) bool {
cn, ok := expr.(*ast.ColumnNameExpr)
if !ok {
return false
}
if cn.Refer.Table.Name.L != c.tableName.L {
return false
}
if c.pkName.L != "" {
return c.pkName.L == cn.Refer.Column.Name.L
}
if c.idx != nil {
return cn.Refer.Column.Name.L == c.idx.Columns[c.columnOffset].Name.L
}
return true
}