expression: fix incompatible last_day func behavior in sql mode (#25953)

[ti-srebot]

cherry-pick #25953 to release-5.1
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/26001

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/tidb.git pr/26001:release-5.1-5a07699871d7

---

Signed-off-by: lzmhhh123 lzmhhh123@gmail.com

What problem does this PR solve?

Problem Summary:

in tidb:

tidb(localhost:4000) > select last_day(str_to_date('202106', '%Y%m'));
+-----------------------------------------+
| last_day(str_to_date('202106', '%Y%m')) |
+-----------------------------------------+
| NULL                                    |
+-----------------------------------------+
1 row in set, 1 warning (0.00 sec)

tidb(localhost:4000) > set @@sql_mode = "";
Query OK, 0 rows affected (0.00 sec)

tidb(localhost:4000) > select last_day(str_to_date('202106', '%Y%m'));
+-----------------------------------------+
| last_day(str_to_date('202106', '%Y%m')) |                                                                                                                                             
+-----------------------------------------+
| NULL                                    |
+-----------------------------------------+
1 row in set, 1 warning (0.00 sec)

tidb(localhost:4000) > show warnings;
+---------+------+----------------------------------------+
| Level   | Code | Message                                |
+---------+------+----------------------------------------+
| Warning | 1292 | Incorrect datetime value: '2021-06-00' |
+---------+------+----------------------------------------+
1 row in set (0.00 sec)

in mysql 8.0.22

mysql > select last_day(str_to_date('202106', '%Y%m'));
+-----------------------------------------+
| last_day(str_to_date('202106', '%Y%m')) |
+-----------------------------------------+
| NULL                                    |
+-----------------------------------------+
1 row in set, 1 warning (0.00 sec)

mysql > set @@sql_mode="";
Query OK, 0 rows affected (0.01 sec)

mysql > select last_day(str_to_date('202106', '%Y%m'));
+-----------------------------------------+
| last_day(str_to_date('202106', '%Y%m')) |
+-----------------------------------------+
| 2021-06-30                              |
+-----------------------------------------+
1 row in set (0.00 sec)

What is changed and how it works?

How it Works:

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Unit test
• Integration test

Release note

• fix incompatible last_day func behavior in sql mode

[ti-srebot]

/run-all-tests

[ti-srebot]

@lzmhhh123 you're already a collaborator in bot's repo.

[AilinKid]

LGTM

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• AilinKid
• tangenta

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[AilinKid]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 7966025