Function as identifier in Tidb is not compatible with Mysql(5.7 and 8.0)

[ramanich1]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

set SQL_MODE='';
drop table if exists  ADDDATE;
create table ADDDATE(a int); 
drop table ADDDATE;
create table ADDDATE (a int);

-- Tidb is treating function ADDDATE as identifer only when a blank space is given in  between ADDDATE (a int);
--Similar functions :
--SESSION_USER	
--SUBDATE
--SYSTEM_USER

2. What did you expect to see? (Required)

mysql> create table ADDDATE(a int); 
Query OK, 0 rows affected (0.01 sec)

mysql> drop table ADDDATE;
Query OK, 0 rows affected (0.00 sec)

mysql> create table ADDDATE (a int);
Query OK, 0 rows affected (0.01 sec)

3. What did you see instead (Required)

mysql> create table ADDDATE(a int); 
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your TiDB version for the right syntax to use line 1 column 20 near "ADDDATE(a int)" 
mysql> drop table ADDDATE;
ERROR 1051 (42S02): Unknown table 'test.ADDDATE'
mysql> create table ADDDATE (a int);
Query OK, 0 rows affected (0.00 sec)

4. What is your TiDB version? (Required)

| Release Version: v5.4.0-alpha-264-g6efa36df6
Edition: Community
Git Commit Hash: 6efa36df6cff325106f67ecfe3d79816ba37ca6a
Git Branch: master
UTC Build Time: 2021-11-29 16:57:51
GoVersion: go1.17.2
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |

[djshow832]

This is weird: according to MySQL document (https://dev.mysql.com/doc/refman/8.0/en/function-resolution.html), ADDDATE should be treated as a function without whitespace between the name and (. It should act as other functions in the list, like COUNT.
However, COUNT obeys the rule but ADDDATE doesn't.

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.