forked from pingcap/tidb
/
explain.go
92 lines (83 loc) · 2.44 KB
/
explain.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 expression
import (
"bytes"
"fmt"
"github.com/pingcap/tidb/util/types"
)
// ExplainInfo implements the Expression interface.
func (expr *ScalarFunction) ExplainInfo() string {
buffer := bytes.NewBufferString(fmt.Sprintf("%s(", expr.FuncName.L))
for i, arg := range expr.GetArgs() {
buffer.WriteString(fmt.Sprintf("%s", arg.ExplainInfo()))
if i+1 < len(expr.GetArgs()) {
buffer.WriteString(", ")
}
}
buffer.WriteString(")")
return buffer.String()
}
// ExplainInfo implements the Expression interface.
func (expr *Column) ExplainInfo() string {
return expr.String()
}
// ExplainInfo implements the Expression interface.
func (expr *Constant) ExplainInfo() string {
valStr, err := expr.Value.ToString()
if err != nil {
if expr.Value.Kind() == types.KindNull {
valStr = "null"
} else {
valStr = "not recognized const value"
}
}
return valStr
}
// ExplainAggFunc generates explain information for a aggregation function.
func ExplainAggFunc(agg AggregationFunction) string {
buffer := bytes.NewBufferString(fmt.Sprintf("%s(", agg.GetName()))
if agg.IsDistinct() {
buffer.WriteString("distinct ")
}
for i, arg := range agg.GetArgs() {
buffer.WriteString(arg.ExplainInfo())
if i+1 < len(agg.GetArgs()) {
buffer.WriteString(", ")
}
}
buffer.WriteString(")")
return buffer.String()
}
// ExplainExpressionList generates explain information for a list of expressions.
func ExplainExpressionList(exprs []Expression) []byte {
buffer := bytes.NewBufferString("")
for i, expr := range exprs {
buffer.WriteString(expr.ExplainInfo())
if i+1 < len(exprs) {
buffer.WriteString(", ")
}
}
return buffer.Bytes()
}
// ExplainColumnList generates explain information for a list of columns.
func ExplainColumnList(cols []*Column) []byte {
buffer := bytes.NewBufferString("")
for i, col := range cols {
buffer.WriteString(col.ExplainInfo())
if i+1 < len(cols) {
buffer.WriteString(", ")
}
}
return buffer.Bytes()
}