[#MDEV-19528] Client warning and log error about FK inconsistency are logically mixed up

Consider the following scenario:

--source include/have_innodb.inc

CREATE TABLE t1 (f INT, UNIQUE(f), KEY(f), FOREIGN KEY (f) REFERENCES t1 (f)) ENGINE=InnoDB;

SET SESSION FOREIGN_KEY_CHECKS= OFF;

ALTER TABLE t1 DROP KEY f;

--source include/restart_mysqld.inc

--error ER_NO_SUCH_TABLE_IN_ENGINE,ER_NO_SUCH_TABLE

SELECT * FROM t1;

SHOW WARNINGS;

SET SESSION FOREIGN_KEY_CHECKS= OFF;

SELECT * FROM t1;

# Cleanup

DROP TABLE t1;

The first SELECT when FOREIGN_KEY_CHECKS=ON, fails:

MariaDB [test]> SELECT * FROM t1;

ERROR 1932 (42S02): Table 'test.t1' doesn't exist in engine

MariaDB [test]> SHOW WARNINGS;

+-------+------+-----------------------------------------+

| Level | Code | Message                                 |

+-------+------+-----------------------------------------+

| Error | 1932 | Table 'test.t1' doesn't exist in engine |

+-------+------+-----------------------------------------+

1 row in set (0.000 sec)

And at the same time produces the warning in the error log:

2019-05-20 16:01:55 9 [Warning] InnoDB: Load table `test`.`t1` failed, the table has missing foreign key indexes. Turn off 'foreign_key_checks' and try again.

It should be the other way round: the message explaining the nature of the problem and suggesting the solution should be the error shown to the user, especially since it only requires a session-level change; while the error about table not existing in the engine is a fairly low-level product which doesn't anyhow help the user, it should go to the error log (if anywhere at all).

[MDEV-19528] Client warning and log error about FK inconsistency are logically mixed up Created: 2019-05-20 Updated: 2021-04-26 Resolved: 2021-04-26
Status:	Closed
Project:	MariaDB Server
Component/s:	Storage Engine - InnoDB
Affects Version/s:	5.5, 10.1, 10.2, 10.3, 10.4
Fix Version/s:	N/A

[MDEV-19528] Client warning and log error about FK inconsistency are logically mixed up Created: 2019-05-20 Updated: 2021-04-26 Resolved: 2021-04-26