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jointree.go
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jointree.go
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/*
Copyright 2021 The Vitess Authors.
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,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package planbuilder
import (
"vitess.io/vitess/go/vt/sqlparser"
"vitess.io/vitess/go/vt/vtgate/semantics"
)
type joinTree struct {
// columns needed to feed other plans
columns []int
// arguments that need to be copied from the LHS/RHS
vars map[string]int
// the children of this plan
lhs, rhs queryTree
leftJoin bool
}
var _ queryTree = (*joinTree)(nil)
func (jp *joinTree) tableID() semantics.TableSet {
return jp.lhs.tableID().Merge(jp.rhs.tableID())
}
func (jp *joinTree) clone() queryTree {
result := &joinTree{
lhs: jp.lhs.clone(),
rhs: jp.rhs.clone(),
leftJoin: jp.leftJoin,
vars: jp.vars,
}
return result
}
func (jp *joinTree) cost() int {
return jp.lhs.cost() + jp.rhs.cost()
}
func (jp *joinTree) pushOutputColumns(columns []*sqlparser.ColName, semTable *semantics.SemTable) ([]int, error) {
var toTheLeft []bool
var lhs, rhs []*sqlparser.ColName
for _, col := range columns {
col.Qualifier.Qualifier = sqlparser.NewTableIdent("")
if semTable.RecursiveDeps(col).IsSolvedBy(jp.lhs.tableID()) {
lhs = append(lhs, col)
toTheLeft = append(toTheLeft, true)
} else {
rhs = append(rhs, col)
toTheLeft = append(toTheLeft, false)
}
}
lhsOffset, err := jp.lhs.pushOutputColumns(lhs, semTable)
if err != nil {
return nil, err
}
rhsOffset, err := jp.rhs.pushOutputColumns(rhs, semTable)
if err != nil {
return nil, err
}
outputColumns := make([]int, len(toTheLeft))
var l, r int
for i, isLeft := range toTheLeft {
outputColumns[i] = i
if isLeft {
jp.columns = append(jp.columns, -lhsOffset[l]-1)
l++
} else {
jp.columns = append(jp.columns, rhsOffset[r]+1)
r++
}
}
return outputColumns, nil
}