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// 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package aggfuncs
import (
"github.com/pingcap/errors"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/util/chunk"
"github.com/pingcap/tidb/util/set"
)
type baseVarPopAggFunc struct {
baseAggFunc
}
type varPop4Float64 struct {
baseVarPopAggFunc
}
type partialResult4VarPopFloat64 struct {
count int64
sum float64
variance float64
}
func (e *varPop4Float64) AllocPartialResult() PartialResult {
return PartialResult(&partialResult4VarPopFloat64{})
}
func (e *varPop4Float64) ResetPartialResult(pr PartialResult) {
p := (*partialResult4VarPopFloat64)(pr)
p.count = 0
p.sum = 0
p.variance = 0
}
func (e *varPop4Float64) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
p := (*partialResult4VarPopFloat64)(pr)
if p.count == 0 {
chk.AppendNull(e.ordinal)
return nil
}
variance := p.variance / float64(p.count)
chk.AppendFloat64(e.ordinal, variance)
return nil
}
func calculateIntermediate(count int64, sum float64, input float64, variance float64) float64 {
t := float64(count)*input - sum
variance += (t * t) / (float64(count * (count - 1)))
return variance
}
func (e *varPop4Float64) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) error {
p := (*partialResult4VarPopFloat64)(pr)
for _, row := range rowsInGroup {
input, isNull, err := e.args[0].EvalReal(sctx, row)
if err != nil {
return errors.Trace(err)
}
if isNull {
continue
}
p.count++
p.sum += input
if p.count > 1 {
p.variance = calculateIntermediate(p.count, p.sum, input, p.variance)
}
}
return nil
}
func calculateMerge(srcCount, dstCount int64, srcSum, dstSum, srcVariance, dstVariance float64) float64 {
srcCountFloat64 := float64(srcCount)
dstCountFloat64 := float64(dstCount)
t := (srcCountFloat64/dstCountFloat64)*dstSum - srcSum
dstVariance += srcVariance + ((dstCountFloat64/srcCountFloat64)/(dstCountFloat64+srcCountFloat64))*t*t
return dstVariance
}
func (e *varPop4Float64) MergePartialResult(sctx sessionctx.Context, src PartialResult, dst PartialResult) error {
p1, p2 := (*partialResult4VarPopFloat64)(src), (*partialResult4VarPopFloat64)(dst)
if p1.count == 0 {
return nil
}
if p2.count == 0 {
p2.count = p1.count
p2.sum = p1.sum
p2.variance = p1.variance
return nil
}
if p2.count != 0 && p1.count != 0 {
p2.variance = calculateMerge(p1.count, p2.count, p1.sum, p2.sum, p1.variance, p2.variance)
p2.count += p1.count
p2.sum += p1.sum
}
return nil
}
type varPop4DistinctFloat64 struct {
baseVarPopAggFunc
}
type partialResult4VarPopDistinctFloat64 struct {
count int64
sum float64
variance float64
valSet set.Float64Set
}
func (e *varPop4DistinctFloat64) AllocPartialResult() PartialResult {
p := new(partialResult4VarPopDistinctFloat64)
p.count = 0
p.sum = 0
p.variance = 0
p.valSet = set.NewFloat64Set()
return PartialResult(p)
}
func (e *varPop4DistinctFloat64) ResetPartialResult(pr PartialResult) {
p := (*partialResult4VarPopDistinctFloat64)(pr)
p.count = 0
p.sum = 0
p.variance = 0
p.valSet = set.NewFloat64Set()
}
func (e *varPop4DistinctFloat64) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
p := (*partialResult4VarPopDistinctFloat64)(pr)
if p.count == 0 {
chk.AppendNull(e.ordinal)
return nil
}
variance := p.variance / float64(p.count)
chk.AppendFloat64(e.ordinal, variance)
return nil
}
func (e *varPop4DistinctFloat64) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) error {
p := (*partialResult4VarPopDistinctFloat64)(pr)
for _, row := range rowsInGroup {
input, isNull, err := e.args[0].EvalReal(sctx, row)
if err != nil {
return errors.Trace(err)
}
if isNull || p.valSet.Exist(input) {
continue
}
p.valSet.Insert(input)
p.count++
p.sum += input
if p.count > 1 {
p.variance = calculateIntermediate(p.count, p.sum, input, p.variance)
}
}
return nil
}