129 lines
3.0 KiB
Go
129 lines
3.0 KiB
Go
// Copyright 2015 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package types
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import (
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"math"
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"github.com/juju/errors"
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"github.com/pingcap/tidb/mysql"
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)
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// RoundFloat rounds float val to the nearest integer value with float64 format, like MySQL Round function.
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// RoundFloat uses default rounding mode, see https://dev.mysql.com/doc/refman/5.7/en/precision-math-rounding.html
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// so rounding use "round half away from zero".
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// e.g, 1.5 -> 2, -1.5 -> -2.
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func RoundFloat(f float64) float64 {
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if math.Abs(f) < 0.5 {
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return 0
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}
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return math.Trunc(f + math.Copysign(0.5, f))
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}
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// Round rounds the argument f to dec decimal places.
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// dec defaults to 0 if not specified. dec can be negative
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// to cause dec digits left of the decimal point of the
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// value f to become zero.
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func Round(f float64, dec int) float64 {
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shift := math.Pow10(dec)
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f = f * shift
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f = RoundFloat(f)
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return f / shift
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}
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func getMaxFloat(flen int, decimal int) float64 {
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intPartLen := flen - decimal
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f := math.Pow10(intPartLen)
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f -= math.Pow10(-decimal)
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return f
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}
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func truncateFloat(f float64, decimal int) float64 {
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pow := math.Pow10(decimal)
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t := (f - math.Floor(f)) * pow
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round := RoundFloat(t)
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f = math.Floor(f) + round/pow
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return f
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}
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// TruncateFloat tries to truncate f.
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// If the result exceeds the max/min float that flen/decimal allowed, returns the max/min float allowed.
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func TruncateFloat(f float64, flen int, decimal int) (float64, error) {
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if math.IsNaN(f) {
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// nan returns 0
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return 0, nil
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}
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maxF := getMaxFloat(flen, decimal)
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if !math.IsInf(f, 0) {
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f = truncateFloat(f, decimal)
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}
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if f > maxF {
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f = maxF
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} else if f < -maxF {
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f = -maxF
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}
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return f, nil
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}
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// CalculateSum adds v to sum.
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func CalculateSum(sum Datum, v Datum) (Datum, error) {
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// for avg and sum calculation
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// avg and sum use decimal for integer and decimal type, use float for others
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// see https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html
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var (
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data Datum
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err error
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)
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switch v.Kind() {
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case KindNull:
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case KindInt64, KindUint64:
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var d mysql.Decimal
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d, err = v.ToDecimal()
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if err == nil {
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data = NewDecimalDatum(d)
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}
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case KindMysqlDecimal:
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data = v
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default:
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var f float64
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f, err = v.ToFloat64()
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if err == nil {
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data = NewFloat64Datum(f)
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}
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}
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if err != nil {
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return data, errors.Trace(err)
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}
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if data.IsNull() {
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return sum, nil
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}
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switch sum.Kind() {
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case KindNull:
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return data, nil
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case KindFloat64, KindMysqlDecimal:
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return ComputePlus(sum, data)
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default:
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return data, errors.Errorf("invalid value %v for aggregate", sum.Kind())
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}
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}
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