tidb util 源码
tidb util 代码
文件路径：/expression/aggregation/util.go
// Copyright 2018 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/errors"
"github.com/pingcap/tidb/sessionctx/stmtctx"
"github.com/pingcap/tidb/types"
"github.com/pingcap/tidb/util/codec"
"github.com/pingcap/tidb/util/mvmap"
)
// distinctChecker stores existing keys and checks if given data is distinct.
type distinctChecker struct {
existingKeys *mvmap.MVMap
key []byte
vals [][]byte
sc *stmtctx.StatementContext
}
// createDistinctChecker creates a new distinct checker.
func createDistinctChecker(sc *stmtctx.StatementContext) *distinctChecker {
return &distinctChecker{
existingKeys: mvmap.NewMVMap(),
sc: sc,
}
}
// Check checks if values is distinct.
func (d *distinctChecker) Check(values []types.Datum) (bool, error) {
d.key = d.key[:0]
var err error
d.key, err = codec.EncodeValue(d.sc, d.key, values...)
if err != nil {
return false, err
}
d.vals = d.existingKeys.Get(d.key, d.vals[:0])
if len(d.vals) > 0 {
return false, nil
}
d.existingKeys.Put(d.key, []byte{})
return true, nil
}
// calculateSum adds v to sum.
func calculateSum(sc *stmtctx.StatementContext, sum, v types.Datum) (data types.Datum, err error) {
// for avg and sum calculation
// avg and sum use decimal for integer and decimal type, use float for others
// see https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html
switch v.Kind() {
case types.KindNull:
case types.KindInt64, types.KindUint64:
var d *types.MyDecimal
d, err = v.ToDecimal(sc)
if err == nil {
data = types.NewDecimalDatum(d)
}
case types.KindMysqlDecimal:
v.Copy(&data)
default:
var f float64
f, err = v.ToFloat64(sc)
if err == nil {
data = types.NewFloat64Datum(f)
}
}
if err != nil {
return data, err
}
if data.IsNull() {
return sum, nil
}
switch sum.Kind() {
case types.KindNull:
return data, nil
case types.KindFloat64, types.KindMysqlDecimal:
return types.ComputePlus(sum, data)
default:
return data, errors.Errorf("invalid value %v for aggregate", sum.Kind())
}
}
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