110 lines
2.9 KiB
Go
110 lines
2.9 KiB
Go
// Copyright 2017 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 aggregation
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import (
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"github.com/juju/errors"
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"github.com/pingcap/tidb/mysql"
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"github.com/pingcap/tidb/sessionctx/stmtctx"
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"github.com/pingcap/tidb/terror"
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"github.com/pingcap/tidb/types"
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)
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type avgFunction struct {
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aggFunction
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}
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// Clone implements Aggregation interface.
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func (af *avgFunction) Clone() Aggregation {
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nf := *af
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for i, arg := range af.Args {
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nf.Args[i] = arg.Clone()
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}
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return &nf
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}
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// GetType implements Aggregation interface.
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func (af *avgFunction) GetType() *types.FieldType {
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ft := types.NewFieldType(mysql.TypeNewDecimal)
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types.SetBinChsClnFlag(ft)
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ft.Flen, ft.Decimal = mysql.MaxRealWidth, af.Args[0].GetType().Decimal
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return ft
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}
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func (af *avgFunction) updateAvg(ctx *AggEvaluateContext, sc *stmtctx.StatementContext, row types.Row) error {
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a := af.Args[1]
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value, err := a.Eval(row)
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if err != nil {
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return errors.Trace(err)
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}
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if value.IsNull() {
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return nil
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}
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if af.Distinct {
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d, err1 := ctx.DistinctChecker.Check([]types.Datum{value})
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if err1 != nil {
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return errors.Trace(err1)
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}
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if !d {
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return nil
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}
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}
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ctx.Value, err = calculateSum(sc, ctx.Value, value)
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if err != nil {
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return errors.Trace(err)
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}
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count, err := af.Args[0].Eval(row)
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if err != nil {
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return errors.Trace(err)
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}
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ctx.Count += count.GetInt64()
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return nil
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}
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// Update implements Aggregation interface.
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func (af *avgFunction) Update(ctx *AggEvaluateContext, sc *stmtctx.StatementContext, row types.Row) error {
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if af.mode == FinalMode {
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return af.updateAvg(ctx, sc, row)
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}
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return af.updateSum(ctx, sc, row)
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}
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// GetResult implements Aggregation interface.
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func (af *avgFunction) GetResult(ctx *AggEvaluateContext) (d types.Datum) {
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var x *types.MyDecimal
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switch ctx.Value.Kind() {
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case types.KindFloat64:
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x = new(types.MyDecimal)
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err := x.FromFloat64(ctx.Value.GetFloat64())
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terror.Log(errors.Trace(err))
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case types.KindMysqlDecimal:
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x = ctx.Value.GetMysqlDecimal()
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default:
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return
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}
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y := types.NewDecFromInt(ctx.Count)
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to := new(types.MyDecimal)
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err := types.DecimalDiv(x, y, to, types.DivFracIncr)
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terror.Log(errors.Trace(err))
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err = to.Round(to, ctx.Value.Frac()+types.DivFracIncr, types.ModeHalfEven)
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terror.Log(errors.Trace(err))
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d.SetMysqlDecimal(to)
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return
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}
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// GetPartialResult implements Aggregation interface.
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func (af *avgFunction) GetPartialResult(ctx *AggEvaluateContext) []types.Datum {
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return []types.Datum{types.NewIntDatum(ctx.Count), ctx.Value}
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}
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