expression: add max_allowed_packet check in concat/concat_ws (#11137)

[sre-bot]

cherry-pick #11137 to release-2.1

---

What problem does this PR solve?

Return NULL and a warning when the result of function concat or concat_ws exceeds max_allowed_packet. ref: #7153

After this PR,

mysql> select @@global.max_allowed_packet;
+-----------------------------+
| @@global.max_allowed_packet |
+-----------------------------+
| 1024                        |
+-----------------------------+
1 row in set (0.00 sec)

mysql> select concat (repeat('a', 10), 'b');
+-------------------------------+
| concat (repeat('a', 10), 'b') |
+-------------------------------+
| aaaaaaaaaab                   |
+-------------------------------+
1 row in set (0.00 sec)

mysql> select concat (repeat('a', 1024), 'b');
+---------------------------------+
| concat (repeat('a', 1024), 'b') |
+---------------------------------+
| NULL                            |
+---------------------------------+
1 row in set, 1 warning (0.01 sec)

mysql> show warnings;
+---------+------+--------------------------------------------------------------------------+
| Level   | Code | Message                                                                  |
+---------+------+--------------------------------------------------------------------------+
| Warning | 1301 | Result of concat() was larger than max_allowed_packet (1024) - truncated |
+---------+------+--------------------------------------------------------------------------+
1 row in set (0.00 sec)

What is changed and how it works?

add max_allowed_packet check during evalString in builtinConcatWSSig and builtinConcatSig

Check List

Tests

• Unit test
• Integration test

Related changes

• Need to cherry-pick to the release branch

[sre-bot]

/run-all-tests

[zz-jason]

LGTM

[wjhuang2016]

LGTM

[sre-bot]

Your auto merge job has been accepted, waiting for 16326, 16310, 16008, 16009

[sre-bot]

/run-all-tests

[zz-jason]

/merge

[sre-bot]

/run-all-tests