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concat.go
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concat.go
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// Copyright 2017 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 aggregation
import (
"bytes"
"fmt"
"github.com/cznic/mathutil"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/sessionctx/stmtctx"
"github.com/pingcap/tidb/types"
"github.com/pingcap/tidb/util/chunk"
"github.com/pkg/errors"
)
type concatFunction struct {
aggFunction
separator string
sepInited bool
maxLen uint64
// According to MySQL, a 'group_concat' function generates exactly one 'truncated' warning during its life time, no matter
// how many group actually truncated. 'truncated' acts as a sentinel to indicate whether this warning has already been
// generated.
truncated bool
}
func (cf *concatFunction) writeValue(evalCtx *AggEvaluateContext, val types.Datum) {
if val.Kind() == types.KindBytes {
evalCtx.Buffer.Write(val.GetBytes())
} else {
evalCtx.Buffer.WriteString(fmt.Sprintf("%v", val.GetValue()))
}
}
func (cf *concatFunction) initSeparator(sc *stmtctx.StatementContext, row chunk.Row) error {
sepArg := cf.Args[len(cf.Args)-1]
sepDatum, err := sepArg.Eval(row)
if err != nil {
return errors.Trace(err)
}
if sepDatum.IsNull() {
return errors.Errorf("Invalid separator argument.")
}
cf.separator, err = sepDatum.ToString()
return errors.Trace(err)
}
// Update implements Aggregation interface.
func (cf *concatFunction) Update(evalCtx *AggEvaluateContext, sc *stmtctx.StatementContext, row chunk.Row) error {
datumBuf := make([]types.Datum, 0, len(cf.Args))
if !cf.sepInited {
err := cf.initSeparator(sc, row)
if err != nil {
return errors.Trace(err)
}
cf.sepInited = true
}
// The last parameter is the concat separator, we only concat the first "len(cf.Args)-1" parameters.
for i, length := 0, len(cf.Args)-1; i < length; i++ {
value, err := cf.Args[i].Eval(row)
if err != nil {
return errors.Trace(err)
}
if value.IsNull() {
return nil
}
datumBuf = append(datumBuf, value)
}
if cf.HasDistinct {
d, err := evalCtx.DistinctChecker.Check(datumBuf)
if err != nil {
return errors.Trace(err)
}
if !d {
return nil
}
}
if evalCtx.Buffer == nil {
evalCtx.Buffer = &bytes.Buffer{}
} else {
evalCtx.Buffer.WriteString(cf.separator)
}
for _, val := range datumBuf {
cf.writeValue(evalCtx, val)
}
if cf.maxLen > 0 && uint64(evalCtx.Buffer.Len()) > cf.maxLen {
i := mathutil.MaxInt
if uint64(i) > cf.maxLen {
i = int(cf.maxLen)
}
evalCtx.Buffer.Truncate(i)
if !cf.truncated {
sc.AppendWarning(expression.ErrCutValueGroupConcat)
}
cf.truncated = true
}
return nil
}
// GetResult implements Aggregation interface.
func (cf *concatFunction) GetResult(evalCtx *AggEvaluateContext) (d types.Datum) {
if evalCtx.Buffer != nil {
d.SetString(evalCtx.Buffer.String())
} else {
d.SetNull()
}
return d
}
func (cf *concatFunction) ResetContext(sc *stmtctx.StatementContext, evalCtx *AggEvaluateContext) {
if cf.HasDistinct {
evalCtx.DistinctChecker = createDistinctChecker(sc)
}
evalCtx.Buffer = nil
}
// GetPartialResult implements Aggregation interface.
func (cf *concatFunction) GetPartialResult(evalCtx *AggEvaluateContext) []types.Datum {
return []types.Datum{cf.GetResult(evalCtx)}
}