Django 2.0.7 broke regex lookup on MariaDB

[Michal Čihař]

Since Django 2.0.7 it fails to do regex lookups on MariaDB. The problem is in code introduced for #29451 - it assumes that MariaDB 10.3 has REGEXP_LIKE what is not true.

The exception is:

Traceback (most recent call last):
  File "/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/django/db/backends/utils.py", line 85, in _execute
    return self.cursor.execute(sql, params)
  File "/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/django/db/backends/mysql/base.py", line 71, in execute
    return self.cursor.execute(query, args)
  File "/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/MySQLdb/cursors.py", line 250, in execute
    self.errorhandler(self, exc, value)
  File "/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/MySQLdb/connections.py", line 50, in defaulterrorhandler
    raise errorvalue
  File "/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/MySQLdb/cursors.py", line 247, in execute
    res = self._query(query)
  File "/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/MySQLdb/cursors.py", line 412, in _query
    rowcount = self._do_query(q)
  File "/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/MySQLdb/cursors.py", line 375, in _do_query
    db.query(q)
  File "/home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages/MySQLdb/connections.py", line 276, in query
    _mysql.connection.query(self, query)
_mysql_exceptions.OperationalError: (1305, 'FUNCTION test_weblate.REGEXP_LIKE does not exist')

[Tim Graham]

Django doesn't officially support MariaDB. There's been some ​discussion about adding support. There are some other tickets like #27676.

[Michal Čihař]

The problem I see is that it worked just fine all versions up to 2.0.7 and it broke in 2.0.7 due to fix for MySQL 8.0. The other tickets seem to be about adding support for new features introduced by MariaDB, while this one is about fixing what used to work before.

​https://github.com/django/django/pull/10133 would work on 2.0 just fine in case you decide to use it as a fix.

[Claude Paroz]

Even if it is not officially supported, I think we should do everything we can to not break it.
I have sites in production with MariaDB!

[Tom Forbes]

It would be possible to fix the patch I made by detecting MariaDB (or more specifically, MySQL) and triggering the correct implementation?

[Claude Paroz]

Absolutely, but patches are waiting for a CI instance with MariaDB. Even if we know there are some failures with MariaDB, at least this would prevent massive breakage like this one (I don't blame you or anyone else, to be clear).