github.com/whtcorpsinc/milevadb-prod@v0.0.0-20211104133533-f57f4be3b597/interlock/aggfuncs/func_varsamp.go (about)

     1  // Copyright 2020 WHTCORPS INC, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package aggfuncs
    15  
    16  import (
    17  	"github.com/whtcorpsinc/milevadb/stochastikctx"
    18  	"github.com/whtcorpsinc/milevadb/soliton/chunk"
    19  )
    20  
    21  type varSamp4Float64 struct {
    22  	varPop4Float64
    23  }
    24  
    25  func (e *varSamp4Float64) AppendFinalResult2Chunk(sctx stochastikctx.Context, pr PartialResult, chk *chunk.Chunk) error {
    26  	p := (*partialResult4VarPopFloat64)(pr)
    27  	if p.count <= 1 {
    28  		chk.AppendNull(e.ordinal)
    29  		return nil
    30  	}
    31  	variance := p.variance / float64(p.count-1)
    32  	chk.AppendFloat64(e.ordinal, variance)
    33  	return nil
    34  }
    35  
    36  type varSamp4DistinctFloat64 struct {
    37  	varPop4DistinctFloat64
    38  }
    39  
    40  func (e *varSamp4DistinctFloat64) AppendFinalResult2Chunk(sctx stochastikctx.Context, pr PartialResult, chk *chunk.Chunk) error {
    41  	p := (*partialResult4VarPoFIDelistinctFloat64)(pr)
    42  	if p.count <= 1 {
    43  		chk.AppendNull(e.ordinal)
    44  		return nil
    45  	}
    46  	variance := p.variance / float64(p.count-1)
    47  	chk.AppendFloat64(e.ordinal, variance)
    48  	return nil
    49  }