tidb func_percent_rank 源码
tidb func_percent_rank 代码
文件路径：/executor/aggfuncs/func_percent_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 (
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/util/chunk"
)
// percentRank calculates the percentage of partition values less than the value in the current row, excluding the highest value.
// It can be calculated as `(rank - 1) / (total_rows_in_set - 1).
type percentRank struct {
baseAggFunc
rowComparer
}
func (pr *percentRank) AllocPartialResult() (partial PartialResult, memDelta int64) {
return PartialResult(&partialResult4Rank{}), DefPartialResult4RankSize
}
func (pr *percentRank) ResetPartialResult(partial PartialResult) {
p := (*partialResult4Rank)(partial)
p.curIdx = 0
p.lastRank = 0
p.rows = p.rows[:0]
}
func (pr *percentRank) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, partial PartialResult) (memDelta int64, err error) {
p := (*partialResult4Rank)(partial)
p.rows = append(p.rows, rowsInGroup...)
memDelta += int64(len(rowsInGroup)) * DefRowSize
return memDelta, nil
}
func (pr *percentRank) AppendFinalResult2Chunk(sctx sessionctx.Context, partial PartialResult, chk *chunk.Chunk) error {
p := (*partialResult4Rank)(partial)
numRows := int64(len(p.rows))
p.curIdx++
if p.curIdx == 1 {
p.lastRank = 1
chk.AppendFloat64(pr.ordinal, 0)
return nil
}
if pr.compareRows(p.rows[p.curIdx-2], p.rows[p.curIdx-1]) == 0 {
chk.AppendFloat64(pr.ordinal, float64(p.lastRank-1)/float64(numRows-1))
return nil
}
p.lastRank = p.curIdx
chk.AppendFloat64(pr.ordinal, float64(p.lastRank-1)/float64(numRows-1))
return nil
}
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