Return type of DATE_ADD is wrong

[Defined2014]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

select DATE_ADD('2001-01-01 00:00:00.000000', INTERVAL 1 SECOND);

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

mysql> select DATE_ADD('2001-01-01 00:00:00.000000', INTERVAL 1 SECOND);
+-----------------------------------------------------------+
| DATE_ADD('2001-01-01 00:00:00.000000', INTERVAL 1 SECOND) |
+-----------------------------------------------------------+
| 2001-01-01 00:00:01                                       |
+-----------------------------------------------------------+
1 row in set (0.00 sec)

3. What did you see instead (Required)

mysql> select DATE_ADD('2001-01-01 00:00:00.000000', INTERVAL 1 SECOND);
+----------------------------------------------------------------------------------------------------------------------+
| DATE_ADD('2001-01-01 00:00:00.000000', INTERVAL 1 SECOND)                                                            |
+----------------------------------------------------------------------------------------------------------------------+
| 0x323030312D30312D30312030303A30303A3031                                                                             |
+----------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

4. What is your TiDB version? (Required)

7fd298d@master

[Defined2014]

Same as date_sub.

[Defined2014]

/assign

[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.

[Defined2014]

/severity major