support INTERVAL + expr

src/sql/parser/sql_parser_mysql_mode.y

@@ -1278,6 +1278,15 @@ bit_expr '|' bit_expr %prec '|'
   check_ret(setup_token_pos_info_and_dup_string($$, result, @1.first_column, @4.last_column),
             &@1, result);
 }
+| INTERVAL expr date_unit '+' bit_expr
+{
+  ParseNode *params = NULL;
+  malloc_non_terminal_node(params, result->malloc_pool_, T_EXPR_LIST, 3, $5, $2, $3);
+  make_name_node($$, result->malloc_pool_, "date_add");
+  malloc_non_terminal_node($$, result->malloc_pool_, T_FUN_SYS, 2, $$, params);
+  check_ret(setup_token_pos_info_and_dup_string($$, result, @1.first_column, @4.last_column),
+            &@1, result);
+}
 | bit_expr '-' INTERVAL expr date_unit %prec '-'
 {
   ParseNode *params = NULL;