tidb sort 源码
tidb sort 代码
文件路径：/planner/implementation/sort.go
// 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,
// 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 implementation
import (
"math"
plannercore "github.com/pingcap/tidb/planner/core"
"github.com/pingcap/tidb/planner/memo"
)
// SortImpl implementation of PhysicalSort.
type SortImpl struct {
baseImpl
}
// NewSortImpl creates a new sort Implementation.
func NewSortImpl(sort *plannercore.PhysicalSort) *SortImpl {
return &SortImpl{baseImpl{plan: sort}}
}
// CalcCost calculates the cost of the sort Implementation.
func (impl *SortImpl) CalcCost(_ float64, children ...memo.Implementation) float64 {
cnt := math.Min(children[0].GetPlan().Stats().RowCount, impl.plan.GetChildReqProps(0).ExpectedCnt)
sort := impl.plan.(*plannercore.PhysicalSort)
impl.cost = sort.GetCost(cnt, children[0].GetPlan().Schema()) + children[0].GetCost()
return impl.cost
}
// AttachChildren implements Implementation AttachChildren interface.
func (impl *SortImpl) AttachChildren(children ...memo.Implementation) memo.Implementation {
sort := impl.plan.(*plannercore.PhysicalSort)
sort.SetChildren(children[0].GetPlan())
// When the Sort orderByItems contain ScalarFunction, we need
// to inject two Projections below and above the Sort.
impl.plan = plannercore.InjectProjBelowSort(sort, sort.ByItems)
return impl
}
// NominalSortImpl is the implementation of NominalSort.
type NominalSortImpl struct {
baseImpl
}
// AttachChildren implements Implementation AttachChildren interface.
func (*NominalSortImpl) AttachChildren(children ...memo.Implementation) memo.Implementation {
return children[0]
}
// NewNominalSortImpl creates a new NominalSort Implementation.
func NewNominalSortImpl(sort *plannercore.NominalSort) *NominalSortImpl {
return &NominalSortImpl{baseImpl{plan: sort}}
}
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