tidb count 源码
tidb count 代码
文件路径：/expression/aggregation/count.go
// 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,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package aggregation
import (
"github.com/pingcap/tidb/sessionctx/stmtctx"
"github.com/pingcap/tidb/types"
"github.com/pingcap/tidb/util/chunk"
)
type countFunction struct {
aggFunction
}
// Update implements Aggregation interface.
func (cf *countFunction) Update(evalCtx *AggEvaluateContext, sc *stmtctx.StatementContext, row chunk.Row) error {
var datumBuf []types.Datum
if cf.HasDistinct {
datumBuf = make([]types.Datum, 0, len(cf.Args))
}
for _, a := range cf.Args {
value, err := a.Eval(row)
if err != nil {
return err
}
if value.IsNull() {
return nil
}
if cf.Mode == FinalMode || cf.Mode == Partial2Mode {
evalCtx.Count += value.GetInt64()
}
if cf.HasDistinct {
datumBuf = append(datumBuf, value)
}
}
if cf.HasDistinct {
d, err := evalCtx.DistinctChecker.Check(datumBuf)
if err != nil {
return err
}
if !d {
return nil
}
}
if cf.Mode == CompleteMode || cf.Mode == Partial1Mode {
evalCtx.Count++
}
return nil
}
func (cf *countFunction) ResetContext(sc *stmtctx.StatementContext, evalCtx *AggEvaluateContext) {
if cf.HasDistinct {
evalCtx.DistinctChecker = createDistinctChecker(sc)
}
evalCtx.Count = 0
}
// GetResult implements Aggregation interface.
func (cf *countFunction) GetResult(evalCtx *AggEvaluateContext) (d types.Datum) {
d.SetInt64(evalCtx.Count)
return d
}
// GetPartialResult implements Aggregation interface.
func (cf *countFunction) GetPartialResult(evalCtx *AggEvaluateContext) []types.Datum {
return []types.Datum{cf.GetResult(evalCtx)}
}
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