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checker.go
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/
checker.go
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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 ranger
import (
"github.com/pingcap/tidb/ast"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/model"
"github.com/pingcap/tidb/types"
)
// conditionChecker checks if this condition can be pushed to index plan.
type conditionChecker struct {
colName model.CIStr
shouldReserve bool // check if a access condition should be reserved in filter conditions.
length int
}
func (c *conditionChecker) check(condition expression.Expression) bool {
switch x := condition.(type) {
case *expression.ScalarFunction:
return c.checkScalarFunction(x)
case *expression.Column:
return c.checkColumn(x)
case *expression.Constant:
return true
}
return false
}
func (c *conditionChecker) checkScalarFunction(scalar *expression.ScalarFunction) bool {
switch scalar.FuncName.L {
case ast.LogicOr, ast.LogicAnd:
return c.check(scalar.GetArgs()[0]) && c.check(scalar.GetArgs()[1])
case ast.EQ, ast.NE, ast.GE, ast.GT, ast.LE, ast.LT:
if _, ok := scalar.GetArgs()[0].(*expression.Constant); ok {
if c.checkColumn(scalar.GetArgs()[1]) {
return scalar.FuncName.L != ast.NE || c.length == types.UnspecifiedLength
}
}
if _, ok := scalar.GetArgs()[1].(*expression.Constant); ok {
if c.checkColumn(scalar.GetArgs()[0]) {
return scalar.FuncName.L != ast.NE || c.length == types.UnspecifiedLength
}
}
case ast.IsNull, ast.IsTruth, ast.IsFalsity:
return c.checkColumn(scalar.GetArgs()[0])
case ast.UnaryNot:
// TODO: support "not like" convert to access conditions.
if s, ok := scalar.GetArgs()[0].(*expression.ScalarFunction); ok {
if s.FuncName.L == ast.Like {
return false
}
} else {
// "not column" or "not constant" can't lead to a range.
return false
}
return c.check(scalar.GetArgs()[0])
case ast.In:
if !c.checkColumn(scalar.GetArgs()[0]) {
return false
}
for _, v := range scalar.GetArgs()[1:] {
if _, ok := v.(*expression.Constant); !ok {
return false
}
}
return true
case ast.Like:
return c.checkLikeFunc(scalar)
case ast.GetParam:
return true
}
return false
}
func (c *conditionChecker) checkLikeFunc(scalar *expression.ScalarFunction) bool {
if !c.checkColumn(scalar.GetArgs()[0]) {
return false
}
pattern, ok := scalar.GetArgs()[1].(*expression.Constant)
if !ok {
return false
}
if pattern.Value.IsNull() {
return false
}
patternStr, err := pattern.Value.ToString()
if err != nil {
return false
}
if len(patternStr) == 0 {
return true
}
escape := byte(scalar.GetArgs()[2].(*expression.Constant).Value.GetInt64())
for i := 0; i < len(patternStr); i++ {
if patternStr[i] == escape {
i++
if i < len(patternStr)-1 {
continue
}
break
}
if i == 0 && (patternStr[i] == '%' || patternStr[i] == '_') {
return false
}
if patternStr[i] == '%' {
if i != len(patternStr)-1 {
c.shouldReserve = true
}
break
}
if patternStr[i] == '_' {
c.shouldReserve = true
break
}
}
return true
}
func (c *conditionChecker) checkColumn(expr expression.Expression) bool {
col, ok := expr.(*expression.Column)
if !ok {
return false
}
if c.colName.L != "" {
return c.colName.L == col.ColName.L
}
return true
}