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166 lines
4.8 KiB
166 lines
4.8 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 ranger
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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/types"
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"github.com/pingcap/tidb/util/collate"
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)
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// conditionChecker checks if this condition can be pushed to index planner.
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type conditionChecker struct {
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colUniqueID int64
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shouldReserve bool // check if a access condition should be reserved in filter conditions.
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length int
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}
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func (c *conditionChecker) check(condition expression.Expression) bool {
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switch x := condition.(type) {
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case *expression.ScalarFunction:
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return c.checkScalarFunction(x)
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case *expression.Column:
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s, _ := condition.(*expression.Column)
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if s.RetType.EvalType() == types.ETString {
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return false
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}
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return c.checkColumn(x)
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case *expression.Constant:
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return true
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}
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return false
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}
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func (c *conditionChecker) checkScalarFunction(scalar *expression.ScalarFunction) bool {
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_, collation := scalar.CharsetAndCollation(scalar.GetCtx())
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switch scalar.FuncName.L {
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case ast.LogicOr, ast.LogicAnd:
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return c.check(scalar.GetArgs()[0]) && c.check(scalar.GetArgs()[1])
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case ast.EQ, ast.NE, ast.GE, ast.GT, ast.LE, ast.LT:
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if _, ok := scalar.GetArgs()[0].(*expression.Constant); ok {
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if c.checkColumn(scalar.GetArgs()[1]) {
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// Checks whether the scalar function is calculated use the collation compatible with the column.
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if scalar.GetArgs()[1].GetType().EvalType() == types.ETString && !collate.CompatibleCollate(scalar.GetArgs()[1].GetType().Collate, collation) {
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return false
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}
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return scalar.FuncName.L != ast.NE || c.length == types.UnspecifiedLength
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}
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}
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if _, ok := scalar.GetArgs()[1].(*expression.Constant); ok {
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if c.checkColumn(scalar.GetArgs()[0]) {
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// Checks whether the scalar function is calculated use the collation compatible with the column.
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if scalar.GetArgs()[0].GetType().EvalType() == types.ETString && !collate.CompatibleCollate(scalar.GetArgs()[0].GetType().Collate, collation) {
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return false
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}
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return scalar.FuncName.L != ast.NE || c.length == types.UnspecifiedLength
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}
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}
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case ast.IsNull:
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return c.checkColumn(scalar.GetArgs()[0])
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case ast.IsTruthWithoutNull, ast.IsTruthWithNull, ast.IsFalsity:
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if s, ok := scalar.GetArgs()[0].(*expression.Column); ok {
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if s.RetType.EvalType() == types.ETString {
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return false
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}
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}
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return c.checkColumn(scalar.GetArgs()[0])
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case ast.UnaryNot:
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// TODO: support "not like" convert to access conditions.
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if s, ok := scalar.GetArgs()[0].(*expression.ScalarFunction); ok {
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if s.FuncName.L == ast.Like {
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return false
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}
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} else {
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// "not column" or "not constant" can't lead to a range.
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return false
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}
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return c.check(scalar.GetArgs()[0])
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case ast.In:
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if !c.checkColumn(scalar.GetArgs()[0]) {
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return false
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}
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if scalar.GetArgs()[1].GetType().EvalType() == types.ETString && !collate.CompatibleCollate(scalar.GetArgs()[0].GetType().Collate, collation) {
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return false
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}
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for _, v := range scalar.GetArgs()[1:] {
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if _, ok := v.(*expression.Constant); !ok {
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return false
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}
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}
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return true
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case ast.Like:
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return c.checkLikeFunc(scalar)
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case ast.GetParam:
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return true
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}
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return false
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}
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func (c *conditionChecker) checkLikeFunc(scalar *expression.ScalarFunction) bool {
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_, collation := scalar.CharsetAndCollation(scalar.GetCtx())
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if !collate.CompatibleCollate(scalar.GetArgs()[0].GetType().Collate, collation) {
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return false
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}
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if !c.checkColumn(scalar.GetArgs()[0]) {
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return false
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}
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pattern, ok := scalar.GetArgs()[1].(*expression.Constant)
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if !ok {
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return false
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}
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if pattern.Value.IsNull() {
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return false
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}
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patternStr, err := pattern.Value.ToString()
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if err != nil {
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return false
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}
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if len(patternStr) == 0 {
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return true
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}
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escape := byte(scalar.GetArgs()[2].(*expression.Constant).Value.GetInt64())
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for i := 0; i < len(patternStr); i++ {
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if patternStr[i] == escape {
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i++
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if i < len(patternStr)-1 {
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continue
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}
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break
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}
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if i == 0 && (patternStr[i] == '%' || patternStr[i] == '_') {
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return false
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}
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if patternStr[i] == '%' {
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if i != len(patternStr)-1 {
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c.shouldReserve = true
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}
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break
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}
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if patternStr[i] == '_' {
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c.shouldReserve = true
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break
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}
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}
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return true
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}
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func (c *conditionChecker) checkColumn(expr expression.Expression) bool {
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col, ok := expr.(*expression.Column)
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if !ok {
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return false
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}
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return c.colUniqueID == col.UniqueID
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}
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