tidb explain 源码
tidb explain 代码
文件路径：/expression/aggregation/explain.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 (
"bytes"
"fmt"
"github.com/pingcap/tidb/parser/ast"
)
// ExplainAggFunc generates explain information for a aggregation function.
func ExplainAggFunc(agg *AggFuncDesc, normalized bool) string {
var buffer bytes.Buffer
fmt.Fprintf(&buffer, "%s(", agg.Name)
if agg.HasDistinct {
buffer.WriteString("distinct ")
}
for i, arg := range agg.Args {
if agg.Name == ast.AggFuncGroupConcat && i == len(agg.Args)-1 {
if len(agg.OrderByItems) > 0 {
buffer.WriteString(" order by ")
for i, item := range agg.OrderByItems {
if item.Desc {
if normalized {
fmt.Fprintf(&buffer, "%s desc", item.Expr.ExplainNormalizedInfo())
} else {
fmt.Fprintf(&buffer, "%s desc", item.Expr.ExplainInfo())
}
} else {
if normalized {
fmt.Fprintf(&buffer, "%s", item.Expr.ExplainNormalizedInfo())
} else {
fmt.Fprintf(&buffer, "%s", item.Expr.ExplainInfo())
}
}
if i+1 < len(agg.OrderByItems) {
buffer.WriteString(", ")
}
}
}
buffer.WriteString(" separator ")
} else if i != 0 {
buffer.WriteString(", ")
}
if normalized {
buffer.WriteString(arg.ExplainNormalizedInfo())
} else {
buffer.WriteString(arg.ExplainInfo())
}
}
buffer.WriteString(")")
return buffer.String()
}
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