resolve conflict

executor/show.go

@@ -1468,17 +1468,11 @@ func (e *ShowExec) fetchShowCreatePlacementPolicy() error {
 func (e *ShowExec) fetchShowCollation() error {
 	var (
 		fieldPatternsLike collate.WildcardPattern
-		FieldFilterEnable bool
 		fieldFilter       string
 	)
 	if e.Extractor != nil {
-		extractor := (e.Extractor).(*plannercore.ShowCollationExtractor)
-		if extractor.FieldPatterns != "" {
-			fieldPatternsLike = collate.GetCollatorByID(collate.CollationName2ID(mysql.UTF8MB4DefaultCollation)).Pattern()
-			fieldPatternsLike.Compile(extractor.FieldPatterns, byte('\\'))
-		}
-		FieldFilterEnable = extractor.Field != ""
-		fieldFilter = extractor.Field
+		fieldPatternsLike = e.Extractor.FieldPatternLike()
+		fieldFilter = e.Extractor.Field()
 	}
 
 	collations := collate.GetSupportedCollations()
@@ -1487,7 +1481,7 @@ func (e *ShowExec) fetchShowCollation() error {
 		if v.IsDefault {
 			isDefault = "Yes"
 		}
-		if FieldFilterEnable && strings.ToLower(v.Name) != fieldFilter {
+		if fieldFilter != "" && strings.ToLower(v.Name) != fieldFilter {
 			continue
 		} else if fieldPatternsLike != nil && !fieldPatternsLike.DoMatch(v.Name) {
 			continue

planner/core/planbuilder.go

@@ -2933,7 +2933,7 @@ func (b *PlanBuilder) buildShow(ctx context.Context, show *ast.ShowStmt) (Plan,
 	isSequence := false
 
 	switch show.Tp {
-	case ast.ShowDatabases, ast.ShowVariables, ast.ShowTables, ast.ShowColumns, ast.ShowTableStatus:
+	case ast.ShowDatabases, ast.ShowVariables, ast.ShowTables, ast.ShowColumns, ast.ShowTableStatus, ast.ShowCollation:
 		if (show.Tp == ast.ShowTables || show.Tp == ast.ShowTableStatus) && p.DBName == "" {
 			return nil, ErrNoDB
 		}

planner/core/show_predicate_extractor.go

@@ -27,9 +27,10 @@ import (
 )
 
 const (
-	fieldKey    = "field"
-	tableKey    = "table"
-	databaseKey = "database"
+	fieldKey     = "field"
+	tableKey     = "table"
+	databaseKey  = "database"
+	collationKey = "collation"
 )
 
 var (
@@ -104,6 +105,8 @@ func (e *ShowBaseExtractor) explainInfo() string {
 		key = tableKey
 	case ast.ShowDatabases:
 		key = databaseKey
+	case ast.ShowCollation:
+		key = collationKey
 	}
 
 	r := new(bytes.Buffer)
@@ -137,25 +140,3 @@ func (e *ShowBaseExtractor) FieldPatternLike() collate.WildcardPattern {
 	fieldPatternsLike.Compile(e.fieldPattern, byte('\\'))
 	return fieldPatternsLike
 }
-
-// ShowCollationExtractor is used to extract some predicates of collations.
-type ShowCollationExtractor struct {
-	ShowBaseExtractor
-}
-
-func (e *ShowCollationExtractor) explainInfo() string {
-	r := new(bytes.Buffer)
-	if len(e.Field) > 0 {
-		r.WriteString(fmt.Sprintf("collation:[%s], ", e.Field))
-	}
-	if len(e.FieldPatterns) > 0 {
-		r.WriteString(fmt.Sprintf("collation_pattern:[%s], ", e.FieldPatterns))
-	}
-
-	// remove the last ", " in the message info
-	s := r.String()
-	if len(s) > 2 {
-		return s[:len(s)-2]
-	}
-	return s
-}