113 lines
3.1 KiB
Go
113 lines
3.1 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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log "github.com/Sirupsen/logrus"
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"github.com/juju/errors"
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"github.com/pingcap/tidb/context"
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"github.com/pingcap/tidb/expression"
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"github.com/pingcap/tidb/sessionctx/variable"
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"github.com/pingcap/tidb/util/types"
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)
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type firstRowFunction struct {
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aggFunction
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}
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// Clone implements Aggregation interface.
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func (ff *firstRowFunction) Clone() Aggregation {
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nf := *ff
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for i, arg := range ff.Args {
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nf.Args[i] = arg.Clone()
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}
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nf.resultMapper = make(aggCtxMapper)
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return &nf
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}
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// GetType implements Aggregation interface.
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func (ff *firstRowFunction) GetType() *types.FieldType {
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return ff.Args[0].GetType()
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}
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// Update implements Aggregation interface.
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func (ff *firstRowFunction) Update(row []types.Datum, groupKey []byte, sc *variable.StatementContext) error {
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ctx := ff.getContext(groupKey)
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if ctx.GotFirstRow {
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return nil
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}
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if len(ff.Args) != 1 {
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return errors.New("Wrong number of args for AggFuncFirstRow")
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}
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value, err := ff.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.Value = value
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ctx.GotFirstRow = true
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return nil
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}
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// StreamUpdate implements Aggregation interface.
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func (ff *firstRowFunction) StreamUpdate(row []types.Datum, sc *variable.StatementContext) error {
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ctx := ff.getStreamedContext()
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if ctx.GotFirstRow {
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return nil
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}
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if len(ff.Args) != 1 {
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return errors.New("Wrong number of args for AggFuncFirstRow")
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}
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value, err := ff.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.Value = value
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ctx.GotFirstRow = true
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return nil
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}
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// GetGroupResult implements Aggregation interface.
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func (ff *firstRowFunction) GetGroupResult(groupKey []byte) types.Datum {
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return ff.getContext(groupKey).Value
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}
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// GetPartialResult implements Aggregation interface.
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func (ff *firstRowFunction) GetPartialResult(groupKey []byte) []types.Datum {
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return []types.Datum{ff.GetGroupResult(groupKey)}
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}
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// GetStreamResult implements Aggregation interface.
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func (ff *firstRowFunction) GetStreamResult() (d types.Datum) {
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if ff.streamCtx == nil {
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return
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}
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d = ff.streamCtx.Value
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ff.streamCtx = nil
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return
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}
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// CalculateDefaultValue implements Aggregation interface.
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func (ff *firstRowFunction) CalculateDefaultValue(schema *expression.Schema, ctx context.Context) (d types.Datum, valid bool) {
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arg := ff.Args[0]
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result, err := expression.EvaluateExprWithNull(ctx, schema, arg)
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if err != nil {
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log.Warnf("Evaluate expr with null failed in function %s, err msg is %s", ff, err.Error())
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return d, false
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}
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if con, ok := result.(*expression.Constant); ok {
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return con.Value, true
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}
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return d, false
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}
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