Add AlterCommentSpec to DDL

go/vt/sqlparser/ast.go

@@ -2014,6 +2014,10 @@ type AlterCollationSpec struct {
 	Collation    string
 }
 
+type AlterCommentSpec struct {
+	Comment string
+}
+
 type ProcedureSpec struct {
 	ProcName        ProcedureName
 	Definer         string
@@ -2272,6 +2276,9 @@ type DDL struct {
 	// AlterCollationSpec is set for CHARACTER SET / COLLATE operations on ALTER statements
 	AlterCollationSpec *AlterCollationSpec
 
+	// AlterCommentSpec is set for COMMENT operations on ALTER statements
+	AlterCommentSpec *AlterCommentSpec
+
 	// EventSpec is set for CREATE EVENT operations
 	EventSpec *EventSpec
 
@@ -2676,6 +2683,8 @@ func (node *DDL) alterFormat(buf *TrackedBuffer) {
 		if len(node.AlterCollationSpec.Collation) > 0 {
 			buf.Myprintf(" collate %s", node.AlterCollationSpec.Collation)
 		}
+	} else if node.AlterCommentSpec != nil {
+		buf.Myprintf(" comment '%s'", node.AlterCommentSpec.Comment)
 	}
 }
 

go/vt/sqlparser/parse_test.go

@@ -4245,7 +4245,19 @@ var (
 		},
 		{
 			input:  "alter table t comment='asdf'",
-			output: "alter table t",
+			output: "alter table t comment 'asdf'",
+		},
+		{
+			input:  `alter table t comment="asdf"`,
+			output: "alter table t comment 'asdf'",
+		},
+		{
+			input:  "alter table t comment 'asdf'",
+			output: "alter table t comment 'asdf'",
+		},
+		{
+			input:  `alter table t comment "asdf"`,
+			output: "alter table t comment 'asdf'",
 		},
 		{
 			input:  "alter table t compression='asdf'",

go/vt/sqlparser/sql.y

@@ -6073,7 +6073,7 @@ alter_table_options:
   }
 | COMMENT_KEYWORD equal_opt STRING
   {
-    $$ = &DDL{Action: AlterStr}
+    $$ = &DDL{Action: AlterStr, AlterCommentSpec: &AlterCommentSpec{Comment: string($3)}}
   }
 | COMPRESSION equal_opt STRING
   {