tidb func_cume_dist 源码
tidb func_cume_dist 代码
文件路径：/executor/aggfuncs/func_cume_dist.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/sessionctx"
"github.com/pingcap/tidb/util/chunk"
)
const (
// DefPartialResult4CumeDistSize is the size of partialResult4CumeDist
DefPartialResult4CumeDistSize = int64(unsafe.Sizeof(partialResult4CumeDist{}))
)
type cumeDist struct {
baseAggFunc
rowComparer
}
type partialResult4CumeDist struct {
curIdx int
lastRank int
rows []chunk.Row
}
func (r *cumeDist) AllocPartialResult() (pr PartialResult, memDelta int64) {
return PartialResult(&partialResult4CumeDist{}), DefPartialResult4CumeDistSize
}
func (r *cumeDist) ResetPartialResult(pr PartialResult) {
p := (*partialResult4CumeDist)(pr)
p.curIdx = 0
p.lastRank = 0
p.rows = p.rows[:0]
}
func (r *cumeDist) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) (memDelta int64, err error) {
p := (*partialResult4CumeDist)(pr)
p.rows = append(p.rows, rowsInGroup...)
memDelta += int64(len(rowsInGroup)) * DefRowSize
return memDelta, nil
}
func (r *cumeDist) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
p := (*partialResult4CumeDist)(pr)
numRows := len(p.rows)
for p.lastRank < numRows && r.compareRows(p.rows[p.curIdx], p.rows[p.lastRank]) == 0 {
p.lastRank++
}
p.curIdx++
chk.AppendFloat64(r.ordinal, float64(p.lastRank)/float64(numRows))
return nil
}
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