feat: define CommentOn task (#295)

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>
Co-authored-by: Ruihang Xia <waynestxia@gmail.com>

proto/greptime/v1/ddl.proto

@@ -39,6 +39,7 @@ message DdlRequest {
     CreateViewExpr create_view = 10;
     DropViewExpr drop_view = 11;
     AlterDatabaseExpr alter_database = 12;
+    CommentOnExpr comment_on = 13;
   }
 }
 
@@ -387,3 +388,22 @@ message DropTriggerExpr {
   string trigger_name = 2;
   bool drop_if_exists = 3;
 }
+
+// The type of object to comment on
+enum CommentObjectType {
+  TABLE = 0;
+  COLUMN = 1;
+  FLOW = 2;
+}
+
+// Comment on a table, column, or flow
+message CommentOnExpr {
+  string catalog_name = 1;
+  string schema_name = 2;
+  CommentObjectType object_type = 3;
+  string object_name = 4;
+  // Column name (only for Column comments)
+  string column_name = 5;
+  // The comment text (null to remove comment)
+  string comment = 6;
+}

proto/greptime/v1/meta/ddl.proto

@@ -98,6 +98,10 @@ message DropTriggerTask {
   DropTriggerExpr drop_trigger = 1;
 }
 
+message CommentOnTask {
+  CommentOnExpr comment_on = 1;
+}
+
 message DdlTaskRequest {
   RequestHeader header = 1;
   QueryContext query_context = 64;
@@ -119,6 +123,7 @@ message DdlTaskRequest {
     AlterDatabaseTask alter_database_task = 15;
     CreateTriggerTask create_trigger_task = 16;
     DropTriggerTask drop_trigger_task = 17;
+    CommentOnTask comment_on_task = 18;
   }
 }