github.com/whtcorpsinc/milevadb-prod@v0.0.0-20211104133533-f57f4be3b597/dbs/memristed/memex/aggregation/explain.go (about)

     1  // Copyright 2020 WHTCORPS INC, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package aggregation
    15  
    16  import (
    17  	"bytes"
    18  	"fmt"
    19  
    20  	"github.com/whtcorpsinc/BerolinaSQL/ast"
    21  )
    22  
    23  // ExplainAggFunc generates explain information for a aggregation function.
    24  func ExplainAggFunc(agg *AggFuncDesc, normalized bool) string {
    25  	var buffer bytes.Buffer
    26  	fmt.Fprintf(&buffer, "%s(", agg.Name)
    27  	if agg.HasDistinct {
    28  		buffer.WriteString("distinct ")
    29  	}
    30  	for i, arg := range agg.Args {
    31  		if agg.Name == ast.AggFuncGroupConcat && i == len(agg.Args)-1 {
    32  			if len(agg.OrderByItems) > 0 {
    33  				buffer.WriteString(" order by ")
    34  				for i, item := range agg.OrderByItems {
    35  					if item.Desc {
    36  						if normalized {
    37  							fmt.Fprintf(&buffer, "%s desc", item.Expr.ExplainNormalizedInfo())
    38  						} else {
    39  							fmt.Fprintf(&buffer, "%s desc", item.Expr.ExplainInfo())
    40  						}
    41  					} else {
    42  						if normalized {
    43  							fmt.Fprintf(&buffer, "%s", item.Expr.ExplainNormalizedInfo())
    44  						} else {
    45  							fmt.Fprintf(&buffer, "%s", item.Expr.ExplainInfo())
    46  						}
    47  					}
    48  
    49  					if i+1 < len(agg.OrderByItems) {
    50  						buffer.WriteString(", ")
    51  					}
    52  				}
    53  			}
    54  			buffer.WriteString(" separator ")
    55  		} else if i != 0 {
    56  			buffer.WriteString(", ")
    57  		}
    58  		if normalized {
    59  			buffer.WriteString(arg.ExplainNormalizedInfo())
    60  		} else {
    61  			buffer.WriteString(arg.ExplainInfo())
    62  		}
    63  	}
    64  	buffer.WriteString(")")
    65  	return buffer.String()
    66  }