tidb func_rank 源码
tidb func_rank 代码
文件路径：/executor/aggfuncs/func_rank.go
// Copyright 2019 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 aggfuncs
import (
"unsafe"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/util/chunk"
)
const (
// DefPartialResult4RankSize is the size of partialResult4Rank
DefPartialResult4RankSize = int64(unsafe.Sizeof(partialResult4Rank{}))
)
type rank struct {
baseAggFunc
isDense bool
rowComparer
}
type partialResult4Rank struct {
curIdx int64
lastRank int64
rows []chunk.Row
}
func (r *rank) AllocPartialResult() (pr PartialResult, memDelta int64) {
return PartialResult(&partialResult4Rank{}), DefPartialResult4RankSize
}
func (r *rank) ResetPartialResult(pr PartialResult) {
p := (*partialResult4Rank)(pr)
p.curIdx = 0
p.lastRank = 0
p.rows = p.rows[:0]
}
func (r *rank) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) (memDelta int64, err error) {
p := (*partialResult4Rank)(pr)
p.rows = append(p.rows, rowsInGroup...)
memDelta += int64(len(rowsInGroup)) * DefRowSize
return memDelta, nil
}
func (r *rank) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
p := (*partialResult4Rank)(pr)
p.curIdx++
if p.curIdx == 1 {
p.lastRank = 1
chk.AppendInt64(r.ordinal, p.lastRank)
return nil
}
if r.compareRows(p.rows[p.curIdx-2], p.rows[p.curIdx-1]) == 0 {
chk.AppendInt64(r.ordinal, p.lastRank)
return nil
}
if r.isDense {
p.lastRank++
} else {
p.lastRank = p.curIdx
}
chk.AppendInt64(r.ordinal, p.lastRank)
return nil
}
type rowComparer struct {
cmpFuncs []chunk.CompareFunc
colIdx []int
}
func buildRowComparer(cols []*expression.Column) rowComparer {
rc := rowComparer{}
rc.colIdx = make([]int, 0, len(cols))
rc.cmpFuncs = make([]chunk.CompareFunc, 0, len(cols))
for _, col := range cols {
cmpFunc := chunk.GetCompareFunc(col.RetType)
if cmpFunc == nil {
continue
}
rc.cmpFuncs = append(rc.cmpFuncs, chunk.GetCompareFunc(col.RetType))
rc.colIdx = append(rc.colIdx, col.Index)
}
return rc
}
func (rc *rowComparer) compareRows(prev, curr chunk.Row) int {
for i, idx := range rc.colIdx {
res := rc.cmpFuncs[i](prev, idx, curr, idx)
if res != 0 {
return res
}
}
return 0
}
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