tidb byitem 源码
tidb byitem 代码
文件路径：/planner/util/byitem.go
// Copyright 2020 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 util
import (
"fmt"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/util/size"
)
// ByItems wraps a "by" item.
type ByItems struct {
Expr expression.Expression
Desc bool
}
// String implements fmt.Stringer interface.
func (by *ByItems) String() string {
if by.Desc {
return fmt.Sprintf("%s true", by.Expr)
}
return by.Expr.String()
}
// Clone makes a copy of ByItems.
func (by *ByItems) Clone() *ByItems {
return &ByItems{Expr: by.Expr.Clone(), Desc: by.Desc}
}
// Equal checks whether two ByItems are equal.
func (by *ByItems) Equal(ctx sessionctx.Context, other *ByItems) bool {
return by.Expr.Equal(ctx, other.Expr) && by.Desc == other.Desc
}
// MemoryUsage return the memory usage of ByItems.
func (by *ByItems) MemoryUsage() (sum int64) {
if by == nil {
return
}
sum = size.SizeOfBool
if by.Expr != nil {
sum += by.Expr.MemoryUsage()
}
return sum
}
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