150 lines
3.8 KiB
Go
150 lines
3.8 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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"github.com/pingcap/tidb/ast"
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"github.com/pingcap/tidb/parser/opcode"
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"github.com/pingcap/tidb/terror"
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)
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// Optimizer error codes.
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const (
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CodeOneColumn terror.ErrCode = iota + 1
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CodeRowColumns
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CodeSameColumns
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CodeMultiWildCard
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CodeUnsupported
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)
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// Optimizer base errors.
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var (
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ErrOneColumn = terror.ClassOptimizer.New(CodeOneColumn, "Operand should contain 1 column(s)")
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ErrRowColumns = terror.ClassOptimizer.New(CodeRowColumns, "Operand should contain >= 2 columns for Row")
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ErrSameColumns = terror.ClassOptimizer.New(CodeRowColumns, "Operands should contain same columns")
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ErrMultiWildCard = terror.ClassOptimizer.New(CodeMultiWildCard, "wildcard field exist more than once")
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ErrUnSupported = terror.ClassOptimizer.New(CodeUnsupported, "unsupported")
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)
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// validate checkes whether the node is valid.
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func validate(node ast.Node) error {
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var v validator
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node.Accept(&v)
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return v.err
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}
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// validator is an ast.Visitor that validates
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// ast Nodes parsed from parser.
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type validator struct {
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err error
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wildCardCount int
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}
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func (v *validator) Enter(in ast.Node) (out ast.Node, skipChildren bool) {
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return in, false
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}
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func (v *validator) Leave(in ast.Node) (out ast.Node, ok bool) {
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switch x := in.(type) {
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case *ast.IsNullExpr:
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v.checkAllOneColumn(x.Expr)
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case *ast.IsTruthExpr:
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v.checkAllOneColumn(x.Expr)
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case *ast.BetweenExpr:
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v.checkAllOneColumn(x.Expr, x.Left, x.Right)
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case *ast.RowExpr:
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if len(x.Values) < 2 {
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v.err = ErrRowColumns
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}
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case *ast.BinaryOperationExpr:
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v.checkBinaryOperation(x)
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case *ast.PatternInExpr:
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v.checkSameColumns(append(x.List, x.Expr)...)
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case *ast.FieldList:
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v.checkFieldList(x)
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case *ast.ByItem:
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v.checkAllOneColumn(x.Expr)
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}
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return in, v.err == nil
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}
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// checkAllOneColumn checks that all expressions have one column.
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// Expression may has more than one column when it is a rowExpr or
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// a Subquery with more than one result fields.
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func (v *validator) checkAllOneColumn(exprs ...ast.ExprNode) {
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for _, expr := range exprs {
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switch x := expr.(type) {
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case *ast.RowExpr:
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v.err = ErrOneColumn
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case *ast.SubqueryExpr:
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if len(x.Query.GetResultFields()) != 1 {
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v.err = ErrOneColumn
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}
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}
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}
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return
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}
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func (v *validator) checkBinaryOperation(x *ast.BinaryOperationExpr) {
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// row constructor only supports comparison operation.
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switch x.Op {
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case opcode.LT, opcode.LE, opcode.GE, opcode.GT, opcode.EQ, opcode.NE, opcode.NullEQ:
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v.checkSameColumns(x.L, x.R)
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default:
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v.checkAllOneColumn(x.L, x.R)
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}
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}
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func columnCount(ex ast.ExprNode) int {
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switch x := ex.(type) {
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case *ast.RowExpr:
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return len(x.Values)
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case *ast.SubqueryExpr:
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return len(x.Query.GetResultFields())
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default:
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return 1
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}
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}
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func (v *validator) checkSameColumns(exprs ...ast.ExprNode) {
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if len(exprs) == 0 {
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return
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}
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count := columnCount(exprs[0])
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for i := 1; i < len(exprs); i++ {
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if columnCount(exprs[i]) != count {
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v.err = ErrSameColumns
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return
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}
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}
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}
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// checkFieldList checks there is only one '*" and each field has only one column,
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func (v *validator) checkFieldList(x *ast.FieldList) {
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var hasWildCard bool
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for _, val := range x.Fields {
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if val.WildCard != nil && val.WildCard.Table.L == "" {
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if hasWildCard {
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v.err = ErrMultiWildCard
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return
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}
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hasWildCard = true
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}
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v.checkAllOneColumn(val.Expr)
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if v.err != nil {
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return
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}
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}
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}
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