tidb func_ntile 源码
tidb func_ntile 代码
文件路径：/executor/aggfuncs/func_ntile.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 (
// DefPartialResult4Ntile is the size of partialResult4Ntile
DefPartialResult4Ntile = int64(unsafe.Sizeof(partialResult4Ntile{}))
)
// ntile divides the partition into n ranked groups and returns the group number a row belongs to.
// e.g. We have 11 rows and n = 3. They will be divided into 3 groups.
//
// First 4 rows belongs to group 1. Following 4 rows belongs to group 2. The last 3 rows belongs to group 3.
type ntile struct {
n uint64
baseAggFunc
}
type partialResult4Ntile struct {
curIdx uint64
curGroupIdx uint64
remainder uint64
quotient uint64
numRows uint64
}
func (n *ntile) AllocPartialResult() (pr PartialResult, memDelta int64) {
return PartialResult(&partialResult4Ntile{curGroupIdx: 1}), DefPartialResult4Ntile
}
func (n *ntile) ResetPartialResult(pr PartialResult) {
p := (*partialResult4Ntile)(pr)
p.curIdx = 0
p.curGroupIdx = 1
p.numRows = 0
}
func (n *ntile) UpdatePartialResult(_ sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) (memDelta int64, err error) {
p := (*partialResult4Ntile)(pr)
p.numRows += uint64(len(rowsInGroup))
// Update the quotient and remainder.
if n.n != 0 {
p.quotient = p.numRows / n.n
p.remainder = p.numRows % n.n
}
return 0, nil
}
func (n *ntile) AppendFinalResult2Chunk(_ sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
p := (*partialResult4Ntile)(pr)
// If the divisor is 0, the arg of NTILE would be NULL. So we just return NULL.
if n.n == 0 {
chk.AppendNull(n.ordinal)
return nil
}
chk.AppendUint64(n.ordinal, p.curGroupIdx)
p.curIdx++
curMaxIdx := p.quotient
if p.curGroupIdx <= p.remainder {
curMaxIdx++
}
if p.curIdx == curMaxIdx {
p.curIdx = 0
p.curGroupIdx++
}
return nil
}
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