Why SHOW ERRORS or SHOW WARNINGS lists only the very last error/warning? - mariadb

Question

I am using the SHOW ERRORS and SHOW WARNIGS statments (on MariaDB 10.10.2) and regardless of the max_error_count is in its default 64 value, the statements above only list the very last error/warning.
Question
How can I list all the last recent errors/warning according the max_error_count variable?

Answer 1

The SQL statement SHOW ERRORS/WARNINGS only returns error or warnings for the last statement which failed or produced a warning. They can be retrieved until another statement produced an error/warning.
If a statement produced more than one error/warnings, then the SHOW ERRORS/WARNINGS return up to max_error warnings.
Example:
delimiter $$
CREATE PROCEDURE p1() BEGIN DROP TABLE whichdoesnotexist; END $$
CREATE PROCEDURE p2() BEGIN CALL p1(); END $$
CREATE PROCEDURE p3() BEGIN CALL p2(); END $$
delimiter ;
SET ##max_error_count=2;
CALL p3();
SHOW WARNIINGS;
+-------+------+----------------------------------------+
| Level | Code | Message |
+-------+------+----------------------------------------+
| Error | 1051 | Unknown table 'test.whichdoesnotexist' |
| Note | 4094 | At line 2 in test.p1 |
+-------+------+----------------------------------------+
SET ##max_error_count=4;
CALL p3();
SHOW WARNINGS;
+-------+------+----------------------------------------+
| Level | Code | Message |
+-------+------+----------------------------------------+
| Error | 1051 | Unknown table 'test.whichdoesnotexist' |
| Note | 4094 | At line 2 in test.p1 |
| Note | 4094 | At line 2 in test.p2 |
| Note | 4094 | At line 2 in test.p3 |
+-------+------+----------------------------------------+
# This will not clear warning/errors
SELECT "1","2","3";
+---+---+---+
| 1 | 2 | 3 |
+---+---+---+
| 1 | 2 | 3 |
+---+---+---+
SHOW WARNINGS;
+-------+------+----------------------------------------+
| Level | Code | Message |
+-------+------+----------------------------------------+
| Error | 1051 | Unknown table 'test.whichdoesnotexist' |
| Note | 4094 | At line 2 in test.p1 |
| Note | 4094 | At line 2 in test.p2 |
| Note | 4094 | At line 2 in test.p3 |
+-------+------+----------------------------------------+

Answer 2

SHOW ERRORS and SHOW WARNINGS only show errors/warnings from the most recent statement in the same session. They will never show anything from previous statements or other sessions. max_error_count will reduce the number shown, but never cause anything else to be shown.
MariaDB [test]> select version();
+-----------------------------------------+
| version() |
+-----------------------------------------+
| 10.10.2-MariaDB-1:10.10.2+maria~ubu2204 |
+-----------------------------------------+
1 row in set (0.001 sec)
MariaDB [test]> select date(d) from (select '' d union all select 20220229) d;
+---------+
| date(d) |
+---------+
| NULL |
| NULL |
+---------+
2 rows in set, 2 warnings (0.002 sec)
MariaDB [test]> show warnings;
+---------+------+--------------------------------------+
| Level | Code | Message |
+---------+------+--------------------------------------+
| Warning | 1292 | Incorrect datetime value: '' |
| Warning | 1292 | Incorrect datetime value: '20220229' |
+---------+------+--------------------------------------+
2 rows in set (0.000 sec)
MariaDB [test]> set session max_error_count=1;
Query OK, 0 rows affected (0.001 sec)
MariaDB [test]> select date(d) from (select '' d union all select 20220229) d;
+---------+
| date(d) |
+---------+
| NULL |
| NULL |
+---------+
2 rows in set, 2 warnings (0.001 sec)
MariaDB [test]> show warnings;
+---------+------+------------------------------+
| Level | Code | Message |
+---------+------+------------------------------+
| Warning | 1292 | Incorrect datetime value: '' |
+---------+------+------------------------------+
1 row in set (0.000 sec)