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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,192 @@ | ||
| // Copyright 2018 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 core | ||
|
|
||
| import ( | ||
| "github.com/pingcap/parser/ast" | ||
| "github.com/pingcap/tidb/expression" | ||
| ) | ||
|
|
||
| type outerJoinEliminator struct { | ||
| } | ||
|
|
||
| // tryToEliminateOuterJoin will eliminate outer join plan base on the following rules | ||
| // 1. outer join elimination: For example left outer join, if the parent only use the | ||
| // columns from left table and the join key of right table(the inner table) is a unique | ||
| // key of the right table. the left outer join can be eliminated. | ||
| // 2. outer join elimination with duplicate agnostic aggregate functions: For example left outer join. | ||
| // If the parent only use the columns from left table with 'distinct' label. The left outer join can | ||
| // be eliminated. | ||
| func (o *outerJoinEliminator) tryToEliminateOuterJoin(p *LogicalJoin, aggCols []*expression.Column, parentSchema *expression.Schema) LogicalPlan { | ||
| var innerChildIdx int | ||
| switch p.JoinType { | ||
| case LeftOuterJoin: | ||
| innerChildIdx = 1 | ||
| case RightOuterJoin: | ||
| innerChildIdx = 0 | ||
| default: | ||
| return p | ||
| } | ||
|
|
||
| outerPlan := p.children[1^innerChildIdx] | ||
| innerPlan := p.children[innerChildIdx] | ||
| // outer join elimination with duplicate agnostic aggregate functions | ||
| if o.isAggColsAllFromOuterTable(outerPlan, aggCols) { | ||
| return outerPlan | ||
| } | ||
| // outer join elimination without duplicate agnostic aggregate functions | ||
| if !o.isParentColsAllFromOuterTable(outerPlan, parentSchema) { | ||
| return p | ||
| } | ||
| innerJoinKeys := o.extractInnerJoinKeys(p, innerChildIdx) | ||
| if o.isInnerJoinKeysContainUniqueKey(innerPlan, innerJoinKeys) { | ||
| return outerPlan | ||
| } | ||
| if o.isInnerJoinKeysContainIndex(innerPlan, innerJoinKeys) { | ||
| return outerPlan | ||
| } | ||
| return p | ||
| } | ||
|
|
||
| // extract join keys as a schema for inner child of a outer join | ||
| func (o *outerJoinEliminator) extractInnerJoinKeys(join *LogicalJoin, innerChildIdx int) *expression.Schema { | ||
| var joinKeys []*expression.Column | ||
| for _, eqCond := range join.EqualConditions { | ||
| joinKeys = append(joinKeys, eqCond.GetArgs()[innerChildIdx].(*expression.Column)) | ||
| } | ||
| return expression.NewSchema(joinKeys...) | ||
| } | ||
|
|
||
| func (o *outerJoinEliminator) isAggColsAllFromOuterTable(outerPlan LogicalPlan, aggCols []*expression.Column) bool { | ||
| if len(aggCols) == 0 { | ||
| return false | ||
| } | ||
| for _, col := range aggCols { | ||
| columnName := &ast.ColumnName{Schema: col.DBName, Table: col.TblName, Name: col.ColName} | ||
| if c, _ := outerPlan.Schema().FindColumn(columnName); c == nil { | ||
| return false | ||
| } | ||
| } | ||
| return true | ||
| } | ||
|
|
||
| // check whether schema cols of join's parent plan are all from outer join table | ||
| func (o *outerJoinEliminator) isParentColsAllFromOuterTable(outerPlan LogicalPlan, parentSchema *expression.Schema) bool { | ||
| if parentSchema == nil { | ||
| return false | ||
| } | ||
| for _, col := range parentSchema.Columns { | ||
| columnName := &ast.ColumnName{Schema: col.DBName, Table: col.TblName, Name: col.ColName} | ||
| if c, _ := outerPlan.Schema().FindColumn(columnName); c == nil { | ||
| return false | ||
| } | ||
| } | ||
| return true | ||
| } | ||
|
|
||
| // check whether one of unique keys sets is contained by inner join keys | ||
| func (o *outerJoinEliminator) isInnerJoinKeysContainUniqueKey(innerPlan LogicalPlan, joinKeys *expression.Schema) bool { | ||
| for _, keyInfo := range innerPlan.Schema().Keys { | ||
| joinKeysContainKeyInfo := true | ||
| for _, col := range keyInfo { | ||
| columnName := &ast.ColumnName{Schema: col.DBName, Table: col.TblName, Name: col.ColName} | ||
| if c, _ := joinKeys.FindColumn(columnName); c == nil { | ||
| joinKeysContainKeyInfo = false | ||
| break | ||
| } | ||
| } | ||
| if joinKeysContainKeyInfo { | ||
| return true | ||
| } | ||
| } | ||
| return false | ||
| } | ||
|
|
||
| // check whether one of index sets is contained by inner join index | ||
| func (o *outerJoinEliminator) isInnerJoinKeysContainIndex(innerPlan LogicalPlan, joinKeys *expression.Schema) bool { | ||
| ds, ok := innerPlan.(*DataSource) | ||
| if !ok { | ||
| return false | ||
| } | ||
| for _, path := range ds.possibleAccessPaths { | ||
| if path.isTablePath { | ||
| continue | ||
| } | ||
| idx := path.index | ||
| if !idx.Unique { | ||
| continue | ||
| } | ||
| joinKeysContainIndex := true | ||
| for _, idxCol := range idx.Columns { | ||
| columnName := &ast.ColumnName{Schema: ds.DBName, Table: ds.tableInfo.Name, Name: idxCol.Name} | ||
| if c, _ := joinKeys.FindColumn(columnName); c == nil { | ||
| joinKeysContainIndex = false | ||
| break | ||
| } | ||
| } | ||
| if joinKeysContainIndex { | ||
| return true | ||
| } | ||
| } | ||
| return false | ||
| } | ||
|
|
||
| // Check whether a LogicalPlan is a LogicalAggregation and its all aggregate functions is duplicate agnostic. | ||
| // Also, check all the args are expression.Column. | ||
| func (o *outerJoinEliminator) isDuplicateAgnosticAgg(p LogicalPlan) (_ bool, cols []*expression.Column) { | ||
| agg, ok := p.(*LogicalAggregation) | ||
| if !ok { | ||
| return false, nil | ||
| } | ||
| cols = agg.groupByCols | ||
| for _, aggDesc := range agg.AggFuncs { | ||
| if !aggDesc.HasDistinct && | ||
| aggDesc.Name != ast.AggFuncFirstRow && | ||
| aggDesc.Name != ast.AggFuncMax && | ||
| aggDesc.Name != ast.AggFuncMin { | ||
| return false, nil | ||
| } | ||
| for _, expr := range aggDesc.Args { | ||
| if col, ok := expr.(*expression.Column); ok { | ||
| cols = append(cols, col) | ||
| } else { | ||
| return false, nil | ||
| } | ||
| } | ||
| } | ||
| return true, cols | ||
| } | ||
|
|
||
| func (o *outerJoinEliminator) doOptimize(p LogicalPlan, aggCols []*expression.Column, parentSchema *expression.Schema) LogicalPlan { | ||
| // check the duplicate agnostic aggregate functions | ||
| if ok, newCols := o.isDuplicateAgnosticAgg(p); ok { | ||
| aggCols = newCols | ||
| } | ||
|
|
||
| newChildren := make([]LogicalPlan, 0, len(p.Children())) | ||
| for _, child := range p.Children() { | ||
| newChild := o.doOptimize(child, aggCols, p.Schema()) | ||
| newChildren = append(newChildren, newChild) | ||
| } | ||
| p.SetChildren(newChildren...) | ||
| join, isJoin := p.(*LogicalJoin) | ||
| if !isJoin { | ||
| return p | ||
| } | ||
| return o.tryToEliminateOuterJoin(join, aggCols, parentSchema) | ||
| } | ||
|
|
||
| func (o *outerJoinEliminator) optimize(p LogicalPlan) (LogicalPlan, error) { | ||
| return o.doOptimize(p, nil, nil), nil | ||
| } |
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