#30786: MySQL backend's has_zoneinfo_database check requires read access to
mysql.time_zone
-------------------------------------+-------------------------------------
Reporter: Andrew | Owner: nobody
Williams |
Type: Bug | Status: new
Component: Database | Version: 2.2
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
The MySQL backend checks whether timezone information has been loaded to
the database by running the query `SELECT 1 FROM mysql.time_zone LIMIT 1`:
https://github.com/django/django/blob/bae05bcf68710cb6dafa51325c3ec83ddda83c39/django/db/backends/mysql/features.py#L70-L75
This code raises the following exception when run using our production
database user and host, though, because the user account doesn't have read
access to the `mysql.time_zone` database table.
`OperationalError: (1142, "SELECT command denied to user
'<dbuser>'@'<dbhost>' for table 'time_zone'")`
I encountered this issue because if the database doesn't have time zones
loaded, the `CONVERT_TZ` calls that Django inserts to certain queries when
`USE_TZ` is True will return NULL, causing queries to silently fail.
After loading in time zones, these CONVERT_TZ calls work as intended, even
without access to `mysql.time_zone`. See
https://code.djangoproject.com/ticket/30726#comment:4 for more info.
Given that `CONVERT_TZ` works without explicit `mysql.time_zone` access,
it'd probably make sense to replace the existing implementation of
`has_zoneinfo_database` with:
{{{
#!python
@cached_property
def has_zoneinfo_database(self):
# Test if the time zone definitions are installed.
with self.connection.cursor() as cursor:
cursor.execute("SELECT CONVERT_TZ('2019-09-19 1:00:00', 'UTC',
'UTC')")
return cursor.fetchone()[0] is not None
}}}
I can submit a PR with this change if you'd like. Alternatively, with the
existing code, it'd be worth documenting somewhere that for MySQL
backends, having access to `mysql.time_zone` is required.
--
Ticket URL: <https://code.djangoproject.com/ticket/30786>
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