expression: check max_allowed_packet constraint for function insert (…

[eurekaka]

What problem does this PR solve?

Return NULL and a warning when the result of function insert exceeds max_allowed_packet.

Before this PR, SELECT INSERT('abc', 1, -1, 'abcd'); would return result 'abcd' even if @@global.max_allowed_packet is set 3.

After this PR:

mysql> select @@max_allowed_packet;
+----------------------+
| @@max_allowed_packet |
+----------------------+
| 3                    |
+----------------------+
1 row in set (0.00 sec)

mysql> select insert('abc', 1, -1, 'abc');
+-----------------------------+
| insert('abc', 1, -1, 'abc') |
+-----------------------------+
| abc                         |
+-----------------------------+
1 row in set (0.00 sec)

mysql> select insert('abc', 1, -1, 'abcd');
+------------------------------+
| insert('abc', 1, -1, 'abcd') |
+------------------------------+
| NULL                         |
+------------------------------+
1 row in set, 1 warning (0.00 sec)

mysql> show warnings;
+---------+------+-----------------------------------------------------------------------+
| Level   | Code | Message                                                               |
+---------+------+-----------------------------------------------------------------------+
| Warning | 1301 | Result of insert() was larger than max_allowed_packet (3) - truncated |
+---------+------+-----------------------------------------------------------------------+
1 row in set (0.00 sec)

What is changed and how it works?

• check result length in valString method of builtinInsertSig and builtinInsertBinarySig against max_allowed_packet;

Check List

Tests

• Unit test

Related changes

• Need to be included in the release note

[zz-jason]

LGTM
@XuHuaiyu @lamxTyler PTAL

[zz-jason]

/run-all-tests tidb-test=release-2.0 tikv=release-2.0 pd=release-2.0

[XuHuaiyu]

LGTM

[eurekaka]

/run-unit-test tidb-test=release-2.0 tikv=release-2.0 pd=release-2.0

[zz-jason]

/run-unit-test

[alivxxx]

/run-all-tests tidb-test=release-2.0 tikv=release-2.0 pd=release-2.0