434 lines
15 KiB
Go
434 lines
15 KiB
Go
// Copyright 2016 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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// // 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 plan
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import (
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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/expression"
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"github.com/pingcap/tidb/model"
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"github.com/pingcap/tidb/mysql"
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"github.com/pingcap/tidb/util/types"
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)
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type ppdSolver struct{}
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func (s *ppdSolver) optimize(lp LogicalPlan, _ context.Context, _ *idAllocator) (LogicalPlan, error) {
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_, p, err := lp.PredicatePushDown(nil)
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return p, errors.Trace(err)
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}
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func addSelection(p Plan, child LogicalPlan, conditions []expression.Expression, allocator *idAllocator) error {
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conditions = expression.PropagateConstant(p.context(), conditions)
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selection := Selection{Conditions: conditions}.init(allocator, p.context())
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selection.SetSchema(child.Schema().Clone())
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return InsertPlan(p, child, selection)
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}
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// PredicatePushDown implements LogicalPlan PredicatePushDown interface.
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func (p *Selection) PredicatePushDown(predicates []expression.Expression) ([]expression.Expression, LogicalPlan, error) {
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retConditions, child, err := p.children[0].(LogicalPlan).PredicatePushDown(append(p.Conditions, predicates...))
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if err != nil {
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return nil, nil, errors.Trace(err)
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}
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if len(retConditions) > 0 {
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p.Conditions = expression.PropagateConstant(p.ctx, retConditions)
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return nil, p, nil
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}
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err = RemovePlan(p)
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if err != nil {
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return nil, nil, errors.Trace(err)
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}
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return nil, child, nil
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}
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// PredicatePushDown implements LogicalPlan PredicatePushDown interface.
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func (p *DataSource) PredicatePushDown(predicates []expression.Expression) ([]expression.Expression, LogicalPlan, error) {
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if UseDAGPlanBuilder(p.ctx) {
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_, p.pushedDownConds, predicates = expression.ExpressionsToPB(p.ctx.GetSessionVars().StmtCtx, predicates, p.ctx.GetClient())
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}
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return predicates, p, nil
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}
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// PredicatePushDown implements LogicalPlan PredicatePushDown interface.
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func (p *TableDual) PredicatePushDown(predicates []expression.Expression) ([]expression.Expression, LogicalPlan, error) {
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return predicates, p, nil
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}
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// PredicatePushDown implements LogicalPlan PredicatePushDown interface.
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func (p *LogicalJoin) PredicatePushDown(predicates []expression.Expression) (ret []expression.Expression, retPlan LogicalPlan, err error) {
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err = outerJoinSimplify(p, predicates)
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if err != nil {
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return nil, nil, errors.Trace(err)
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}
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groups, valid := tryToGetJoinGroup(p)
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if valid {
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e := joinReOrderSolver{allocator: p.allocator, ctx: p.ctx}
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e.reorderJoin(groups, predicates)
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newJoin := e.resultJoin
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if len(p.parents) > 0 {
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parent := p.parents[0]
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newJoin.SetParents(parent)
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parent.ReplaceChild(p, newJoin)
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}
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return newJoin.PredicatePushDown(predicates)
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}
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var leftCond, rightCond []expression.Expression
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retPlan = p
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leftPlan := p.children[0].(LogicalPlan)
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rightPlan := p.children[1].(LogicalPlan)
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var (
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equalCond []*expression.ScalarFunction
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leftPushCond, rightPushCond, otherCond []expression.Expression
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)
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if p.JoinType != InnerJoin {
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equalCond, leftPushCond, rightPushCond, otherCond = extractOnCondition(predicates, leftPlan, rightPlan)
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} else {
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tempCond := make([]expression.Expression, 0, len(p.LeftConditions)+len(p.RightConditions)+len(p.EqualConditions)+len(p.OtherConditions)+len(predicates))
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tempCond = append(tempCond, p.LeftConditions...)
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tempCond = append(tempCond, p.RightConditions...)
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tempCond = append(tempCond, expression.ScalarFuncs2Exprs(p.EqualConditions)...)
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tempCond = append(tempCond, p.OtherConditions...)
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tempCond = append(tempCond, predicates...)
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equalCond, leftPushCond, rightPushCond, otherCond = extractOnCondition(expression.PropagateConstant(p.ctx, tempCond), leftPlan, rightPlan)
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}
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switch p.JoinType {
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case LeftOuterJoin, LeftOuterSemiJoin:
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rightCond = p.RightConditions
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p.RightConditions = nil
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leftCond = leftPushCond
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ret = append(expression.ScalarFuncs2Exprs(equalCond), otherCond...)
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ret = append(ret, rightPushCond...)
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case RightOuterJoin:
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leftCond = p.LeftConditions
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p.LeftConditions = nil
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rightCond = rightPushCond
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ret = append(expression.ScalarFuncs2Exprs(equalCond), otherCond...)
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ret = append(ret, leftPushCond...)
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case SemiJoin:
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equalCond, leftPushCond, rightPushCond, otherCond = extractOnCondition(predicates, leftPlan, rightPlan)
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leftCond = append(p.LeftConditions, leftPushCond...)
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rightCond = append(p.RightConditions, rightPushCond...)
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p.LeftConditions = nil
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p.RightConditions = nil
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case InnerJoin:
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p.LeftConditions = nil
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p.RightConditions = nil
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p.EqualConditions = equalCond
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p.OtherConditions = otherCond
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leftCond = leftPushCond
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rightCond = rightPushCond
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}
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leftRet, _, err1 := leftPlan.PredicatePushDown(leftCond)
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if err1 != nil {
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return nil, nil, errors.Trace(err1)
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}
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rightRet, _, err2 := rightPlan.PredicatePushDown(rightCond)
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if err2 != nil {
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return nil, nil, errors.Trace(err2)
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}
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if len(leftRet) > 0 {
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err2 = addSelection(p, leftPlan, leftRet, p.allocator)
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if err2 != nil {
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return nil, nil, errors.Trace(err2)
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}
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}
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if len(rightRet) > 0 {
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err2 = addSelection(p, rightPlan, rightRet, p.allocator)
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if err2 != nil {
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return nil, nil, errors.Trace(err2)
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}
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}
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p.updateEQCond()
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for _, eqCond := range p.EqualConditions {
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p.LeftJoinKeys = append(p.LeftJoinKeys, eqCond.GetArgs()[0].(*expression.Column))
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p.RightJoinKeys = append(p.RightJoinKeys, eqCond.GetArgs()[1].(*expression.Column))
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}
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p.mergeSchema()
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p.buildKeyInfo()
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return
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}
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// updateEQCond will extract the arguments of a equal condition that connect two expressions.
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func (p *LogicalJoin) updateEQCond() {
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lChild, rChild := p.children[0], p.children[1]
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var lKeys, rKeys []expression.Expression
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for i := len(p.OtherConditions) - 1; i >= 0; i-- {
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need2Remove := false
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if eqCond, ok := p.OtherConditions[i].(*expression.ScalarFunction); ok && eqCond.FuncName.L == ast.EQ {
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lExpr, rExpr := eqCond.GetArgs()[0], eqCond.GetArgs()[1]
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if expression.ExprFromSchema(lExpr, lChild.Schema()) && expression.ExprFromSchema(rExpr, rChild.Schema()) {
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lKeys = append(lKeys, lExpr)
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rKeys = append(rKeys, rExpr)
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need2Remove = true
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} else if expression.ExprFromSchema(lExpr, rChild.Schema()) && expression.ExprFromSchema(rExpr, lChild.Schema()) {
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lKeys = append(lKeys, rExpr)
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rKeys = append(rKeys, lExpr)
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need2Remove = true
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}
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}
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if need2Remove {
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p.OtherConditions = append(p.OtherConditions[:i], p.OtherConditions[i+1:]...)
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}
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}
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if len(lKeys) > 0 {
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lProj := p.getProj(0)
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rProj := p.getProj(1)
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for i := range lKeys {
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lKey := lProj.appendExpr(lKeys[i])
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rKey := rProj.appendExpr(rKeys[i])
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eqCond, _ := expression.NewFunction(p.ctx, ast.EQ, types.NewFieldType(mysql.TypeTiny), lKey, rKey)
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p.EqualConditions = append(p.EqualConditions, eqCond.(*expression.ScalarFunction))
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}
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}
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}
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func (p *Projection) appendExpr(expr expression.Expression) *expression.Column {
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if col, ok := expr.(*expression.Column); ok {
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return col
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}
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expr = expression.ColumnSubstitute(expr, p.schema, p.Exprs)
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p.Exprs = append(p.Exprs, expr)
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col := &expression.Column{
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FromID: p.id,
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Position: p.schema.Len(),
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ColName: model.NewCIStr(expr.String()),
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RetType: expr.GetType(),
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}
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p.schema.Append(col)
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return col.Clone().(*expression.Column)
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}
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func (p *LogicalJoin) getProj(idx int) *Projection {
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child := p.children[idx]
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proj, ok := child.(*Projection)
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if ok {
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return proj
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}
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proj = Projection{Exprs: make([]expression.Expression, 0, child.Schema().Len())}.init(p.allocator, p.ctx)
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for _, col := range child.Schema().Columns {
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proj.Exprs = append(proj.Exprs, col.Clone())
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}
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proj.SetSchema(child.Schema().Clone())
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child.SetParents(proj)
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proj.SetChildren(child)
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proj.SetParents(p)
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p.children[idx] = proj
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return proj
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}
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// outerJoinSimplify simplifies outer join.
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func outerJoinSimplify(p *LogicalJoin, predicates []expression.Expression) error {
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var innerTable, outerTable LogicalPlan
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child1 := p.children[0].(LogicalPlan)
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child2 := p.children[1].(LogicalPlan)
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var fullConditions []expression.Expression
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if p.JoinType == LeftOuterJoin {
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innerTable = child2
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outerTable = child1
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} else if p.JoinType == RightOuterJoin || p.JoinType == InnerJoin {
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innerTable = child1
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outerTable = child2
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} else {
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return nil
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}
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// first simplify embedded outer join.
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// When trying to simplify an embedded outer join operation in a query,
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// we must take into account the join condition for the embedding outer join together with the WHERE condition.
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if innerPlan, ok := innerTable.(*LogicalJoin); ok {
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fullConditions = concatOnAndWhereConds(p, predicates)
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err := outerJoinSimplify(innerPlan, fullConditions)
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if err != nil {
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return errors.Trace(err)
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}
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}
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if outerPlan, ok := outerTable.(*LogicalJoin); ok {
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if fullConditions != nil {
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fullConditions = concatOnAndWhereConds(p, predicates)
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}
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err := outerJoinSimplify(outerPlan, fullConditions)
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if err != nil {
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return errors.Trace(err)
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}
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}
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if p.JoinType == InnerJoin {
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return nil
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}
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// then simplify embedding outer join.
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canBeSimplified := false
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for _, expr := range predicates {
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isOk, err := isNullRejected(p.ctx, innerTable.Schema(), expr)
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if err != nil {
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return errors.Trace(err)
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}
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if isOk {
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canBeSimplified = true
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break
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}
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}
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if canBeSimplified {
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p.JoinType = InnerJoin
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}
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return nil
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}
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// isNullRejected check whether a condition is null-rejected
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// A condition would be null-rejected in one of following cases:
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// If it is a predicate containing a reference to an inner table that evaluates to UNKNOWN or FALSE when one of its arguments is NULL.
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// If it is a conjunction containing a null-rejected condition as a conjunct.
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// If it is a disjunction of null-rejected conditions.
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func isNullRejected(ctx context.Context, schema *expression.Schema, expr expression.Expression) (bool, error) {
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result, err := expression.EvaluateExprWithNull(ctx, schema, expr)
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if err != nil {
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return false, errors.Trace(err)
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}
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x, ok := result.(*expression.Constant)
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if !ok {
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return false, nil
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}
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sc := ctx.GetSessionVars().StmtCtx
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if x.Value.IsNull() {
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return true, nil
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} else if isTrue, err := x.Value.ToBool(sc); err != nil || isTrue == 0 {
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return true, errors.Trace(err)
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}
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return false, nil
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}
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// concatOnAndWhereConds concatenate ON conditions with WHERE conditions.
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func concatOnAndWhereConds(join *LogicalJoin, predicates []expression.Expression) []expression.Expression {
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equalConds, leftConds, rightConds, otherConds := join.EqualConditions, join.LeftConditions, join.RightConditions, join.OtherConditions
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ans := make([]expression.Expression, 0, len(equalConds)+len(leftConds)+len(rightConds)+len(predicates))
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for _, v := range equalConds {
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ans = append(ans, v)
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}
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ans = append(ans, leftConds...)
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ans = append(ans, rightConds...)
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ans = append(ans, otherConds...)
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ans = append(ans, predicates...)
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return ans
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}
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// PredicatePushDown implements LogicalPlan PredicatePushDown interface.
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func (p *Projection) PredicatePushDown(predicates []expression.Expression) (ret []expression.Expression, retPlan LogicalPlan, err error) {
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retPlan = p
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var push []expression.Expression
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for _, cond := range predicates {
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canSubstitute := true
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extractedCols := expression.ExtractColumns(cond)
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for _, col := range extractedCols {
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id := p.Schema().ColumnIndex(col)
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if _, ok := p.Exprs[id].(*expression.ScalarFunction); ok {
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canSubstitute = false
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break
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}
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}
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if canSubstitute {
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push = append(push, expression.ColumnSubstitute(cond, p.Schema(), p.Exprs))
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} else {
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ret = append(ret, cond)
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}
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}
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child := p.children[0].(LogicalPlan)
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restConds, _, err1 := child.PredicatePushDown(push)
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if err1 != nil {
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return nil, nil, errors.Trace(err1)
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}
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if len(restConds) > 0 {
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err1 = addSelection(p, child, restConds, p.allocator)
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if err1 != nil {
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return nil, nil, errors.Trace(err1)
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}
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}
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return
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}
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// PredicatePushDown implements LogicalPlan PredicatePushDown interface.
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func (p *Union) PredicatePushDown(predicates []expression.Expression) (ret []expression.Expression, retPlan LogicalPlan, err error) {
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retPlan = p
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for _, proj := range p.children {
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newExprs := make([]expression.Expression, 0, len(predicates))
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for _, cond := range predicates {
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newCond := expression.ColumnSubstitute(cond, p.Schema(), expression.Column2Exprs(proj.Schema().Columns))
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newExprs = append(newExprs, newCond)
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}
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retCond, _, err := proj.(LogicalPlan).PredicatePushDown(newExprs)
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if err != nil {
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return nil, nil, errors.Trace(err)
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}
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if len(retCond) != 0 {
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addSelection(p, proj.(LogicalPlan), retCond, p.allocator)
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}
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}
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return
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}
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// getGbyColIndex gets the column's index in the group-by columns.
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func (p *LogicalAggregation) getGbyColIndex(col *expression.Column) int {
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return expression.NewSchema(p.groupByCols...).ColumnIndex(col)
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}
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// PredicatePushDown implements LogicalPlan PredicatePushDown interface.
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func (p *LogicalAggregation) PredicatePushDown(predicates []expression.Expression) (ret []expression.Expression, retPlan LogicalPlan, err error) {
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retPlan = p
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var exprsOriginal []expression.Expression
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var condsToPush []expression.Expression
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for _, fun := range p.AggFuncs {
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exprsOriginal = append(exprsOriginal, fun.GetArgs()[0])
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}
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for _, cond := range predicates {
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switch cond.(type) {
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case *expression.Constant:
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condsToPush = append(condsToPush, cond)
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// Consider SQL list "select sum(b) from t group by a having 1=0". "1=0" is a constant predicate which should be
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// retained and pushed down at the same time. Because we will get a wrong query result that contains one column
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// with value 0 rather than an empty query result.
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ret = append(ret, cond)
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case *expression.ScalarFunction:
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extractedCols := expression.ExtractColumns(cond)
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ok := true
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for _, col := range extractedCols {
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if p.getGbyColIndex(col) == -1 {
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ok = false
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break
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}
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}
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if ok {
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newFunc := expression.ColumnSubstitute(cond.Clone(), p.Schema(), exprsOriginal)
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condsToPush = append(condsToPush, newFunc)
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} else {
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ret = append(ret, cond)
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}
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default:
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ret = append(ret, cond)
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}
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}
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p.baseLogicalPlan.PredicatePushDown(condsToPush)
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return
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}
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// PredicatePushDown implements LogicalPlan PredicatePushDown interface.
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func (p *Limit) PredicatePushDown(predicates []expression.Expression) ([]expression.Expression, LogicalPlan, error) {
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// Limit forbids any condition to push down.
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_, _, err := p.baseLogicalPlan.PredicatePushDown(nil)
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return predicates, p, errors.Trace(err)
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}
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// PredicatePushDown implements LogicalPlan PredicatePushDown interface.
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func (p *MaxOneRow) PredicatePushDown(predicates []expression.Expression) ([]expression.Expression, LogicalPlan, error) {
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// MaxOneRow forbids any condition to push down.
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_, _, err := p.baseLogicalPlan.PredicatePushDown(nil)
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return predicates, p, errors.Trace(err)
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}
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