tidb/executor/aggfuncs/func_max_min.go

// Copyright 2018 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/juju/errors"
	"github.com/pingcap/tidb/sessionctx"
	"github.com/pingcap/tidb/types"
	"github.com/pingcap/tidb/util/chunk"
)

type partialResult4MaxMinInt struct {
	val int64
	// isNull is used to indicates:
	// 1. whether the partial result is the initialization value which should not be compared during evaluation;
	// 2. whether all the values of arg are all null, if so, we should return null as the default value for MAX/MIN.
	isNull bool
}

type partialResult4MaxMinUint struct {
	val    uint64
	isNull bool
}

type partialResult4MaxMinDecimal struct {
	val    types.MyDecimal
	isNull bool
}

type partialResult4MaxMinFloat32 struct {
	val    float32
	isNull bool
}

type partialResult4MaxMinFloat64 struct {
	val    float64
	isNull bool
}

type baseMaxMinAggFunc struct {
	baseAggFunc

	isMax bool
}

type maxMin4Int struct {
	baseMaxMinAggFunc
}

func (e *maxMin4Int) AllocPartialResult() PartialResult {
	p := new(partialResult4MaxMinInt)
	p.isNull = true
	return PartialResult(p)
}

func (e *maxMin4Int) ResetPartialResult(pr PartialResult) {
	p := (*partialResult4MaxMinInt)(pr)
	p.val = 0
	p.isNull = true
}

func (e *maxMin4Int) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
	p := (*partialResult4MaxMinInt)(pr)
	if p.isNull {
		chk.AppendNull(e.ordinal)
		return nil
	}
	chk.AppendInt64(e.ordinal, p.val)
	return nil
}

func (e *maxMin4Int) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) error {
	p := (*partialResult4MaxMinInt)(pr)
	for _, row := range rowsInGroup {
		input, isNull, err := e.args[0].EvalInt(sctx, row)
		if err != nil {
			return errors.Trace(err)
		}
		if isNull {
			continue
		}
		if p.isNull {
			p.val = input
			p.isNull = false
			continue
		}
		if e.isMax && input > p.val || !e.isMax && input < p.val {
			p.val = input
		}
	}
	return nil
}

type maxMin4Uint struct {
	baseMaxMinAggFunc
}

func (e *maxMin4Uint) AllocPartialResult() PartialResult {
	p := new(partialResult4MaxMinUint)
	p.isNull = true
	return PartialResult(p)
}

func (e *maxMin4Uint) ResetPartialResult(pr PartialResult) {
	p := (*partialResult4MaxMinUint)(pr)
	p.val = 0
	p.isNull = true
}

func (e *maxMin4Uint) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
	p := (*partialResult4MaxMinUint)(pr)
	if p.isNull {
		chk.AppendNull(e.ordinal)
		return nil
	}
	chk.AppendUint64(e.ordinal, p.val)
	return nil
}

func (e *maxMin4Uint) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) error {
	p := (*partialResult4MaxMinUint)(pr)
	for _, row := range rowsInGroup {
		input, isNull, err := e.args[0].EvalInt(sctx, row)
		if err != nil {
			return errors.Trace(err)
		}
		if isNull {
			continue
		}
		uintVal := uint64(input)
		if p.isNull {
			p.val = uintVal
			p.isNull = false
			continue
		}
		if e.isMax && uintVal > p.val || !e.isMax && uintVal < p.val {
			p.val = uintVal
		}
	}
	return nil
}

// maxMin4Float32 gets a float32 input and returns a float32 result.
type maxMin4Float32 struct {
	baseMaxMinAggFunc
}

func (e *maxMin4Float32) AllocPartialResult() PartialResult {
	p := new(partialResult4MaxMinFloat32)
	p.isNull = true
	return PartialResult(p)
}

func (e *maxMin4Float32) ResetPartialResult(pr PartialResult) {
	p := (*partialResult4MaxMinFloat32)(pr)
	p.val = 0
	p.isNull = true
}

func (e *maxMin4Float32) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
	p := (*partialResult4MaxMinFloat32)(pr)
	if p.isNull {
		chk.AppendNull(e.ordinal)
		return nil
	}
	chk.AppendFloat32(e.ordinal, p.val)
	return nil
}

func (e *maxMin4Float32) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) error {
	p := (*partialResult4MaxMinFloat32)(pr)
	for _, row := range rowsInGroup {
		input, isNull, err := e.args[0].EvalReal(sctx, row)
		if err != nil {
			return errors.Trace(err)
		}
		if isNull {
			continue
		}
		f := float32(input)
		if p.isNull {
			p.val = f
			p.isNull = false
			continue
		}
		if e.isMax && f > p.val || !e.isMax && f < p.val {
			p.val = f
		}
	}
	return nil
}

type maxMin4Float64 struct {
	baseMaxMinAggFunc
}

func (e *maxMin4Float64) AllocPartialResult() PartialResult {
	p := new(partialResult4MaxMinFloat64)
	p.isNull = true
	return PartialResult(p)
}

func (e *maxMin4Float64) ResetPartialResult(pr PartialResult) {
	p := (*partialResult4MaxMinFloat64)(pr)
	p.val = 0
	p.isNull = true
}

func (e *maxMin4Float64) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
	p := (*partialResult4MaxMinFloat64)(pr)
	if p.isNull {
		chk.AppendNull(e.ordinal)
		return nil
	}
	chk.AppendFloat64(e.ordinal, p.val)
	return nil
}

func (e *maxMin4Float64) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) error {
	p := (*partialResult4MaxMinFloat64)(pr)
	for _, row := range rowsInGroup {
		input, isNull, err := e.args[0].EvalReal(sctx, row)
		if err != nil {
			return errors.Trace(err)
		}
		if isNull {
			continue
		}
		if p.isNull {
			p.val = input
			p.isNull = false
			continue
		}
		if e.isMax && input > p.val || !e.isMax && input < p.val {
			p.val = input
		}
	}
	return nil
}

type maxMin4Decimal struct {
	baseMaxMinAggFunc
}

func (e *maxMin4Decimal) AllocPartialResult() PartialResult {
	p := new(partialResult4MaxMinDecimal)
	p.isNull = true
	return PartialResult(p)
}

func (e *maxMin4Decimal) ResetPartialResult(pr PartialResult) {
	p := (*partialResult4MaxMinDecimal)(pr)
	p.isNull = true
}

func (e *maxMin4Decimal) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
	p := (*partialResult4MaxMinDecimal)(pr)
	if p.isNull {
		chk.AppendNull(e.ordinal)
		return nil
	}
	chk.AppendMyDecimal(e.ordinal, &p.val)
	return nil
}

func (e *maxMin4Decimal) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) error {
	p := (*partialResult4MaxMinDecimal)(pr)
	for _, row := range rowsInGroup {
		input, isNull, err := e.args[0].EvalDecimal(sctx, row)
		if err != nil {
			return errors.Trace(err)
		}
		if isNull {
			continue
		}
		if p.isNull {
			p.val = *input
			p.isNull = false
			continue
		}
		cmp := input.Compare(&p.val)
		if e.isMax && cmp == 1 || !e.isMax && cmp == -1 {
			p.val = *input
		}
	}
	return nil
}