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98 lines
2.7 KiB
98 lines
2.7 KiB
// 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/cznic/mathutil"
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"github.com/pingcap/parser/mysql"
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"github.com/pingcap/parser/terror"
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"github.com/pingcap/tidb/sessionctx/stmtctx"
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"github.com/pingcap/tidb/types"
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"github.com/pingcap/tidb/util/chunk"
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)
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type avgFunction struct {
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aggFunction
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}
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func (af *avgFunction) updateAvg(sc *stmtctx.StatementContext, evalCtx *AggEvaluateContext, row chunk.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 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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evalCtx.Value, err = calculateSum(sc, evalCtx.Value, value)
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if err != nil {
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return 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 err
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}
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evalCtx.Count += count.GetInt64()
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return nil
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}
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func (af *avgFunction) ResetContext(sc *stmtctx.StatementContext, evalCtx *AggEvaluateContext) {
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if af.HasDistinct {
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evalCtx.DistinctChecker = createDistinctChecker(sc)
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}
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evalCtx.Value.SetNull()
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evalCtx.Count = 0
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}
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// Update implements Aggregation interface.
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func (af *avgFunction) Update(evalCtx *AggEvaluateContext, sc *stmtctx.StatementContext, row chunk.Row) (err error) {
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switch af.Mode {
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case Partial1Mode, CompleteMode:
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err = af.updateSum(sc, evalCtx, row)
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case Partial2Mode, FinalMode:
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err = af.updateAvg(sc, evalCtx, row)
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case DedupMode:
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panic("DedupMode is not supported now.")
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}
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return err
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}
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// GetResult implements Aggregation interface.
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func (af *avgFunction) GetResult(evalCtx *AggEvaluateContext) (d types.Datum) {
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switch evalCtx.Value.Kind() {
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case types.KindFloat64:
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sum := evalCtx.Value.GetFloat64()
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d.SetFloat64(sum / float64(evalCtx.Count))
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return
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case types.KindMysqlDecimal:
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x := evalCtx.Value.GetMysqlDecimal()
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y := types.NewDecFromInt(evalCtx.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(err)
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frac := af.RetTp.Decimal
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if frac == -1 {
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frac = mysql.MaxDecimalScale
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}
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err = to.Round(to, mathutil.Min(frac, mysql.MaxDecimalScale), types.ModeHalfEven)
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terror.Log(err)
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d.SetMysqlDecimal(to)
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}
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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(evalCtx *AggEvaluateContext) []types.Datum {
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return []types.Datum{types.NewIntDatum(evalCtx.Count), evalCtx.Value}
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}
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