Hi Matthew,
Am 10.04.2017 um 15:51 schrieb Matthew Pava:
I would argue that your code should be able to run successfully with an empty
database.
I would change your assignment of maxID to this:
maxID = cls.objects.aggregate(Max('id'))['id__max'] or 0
Normally, I would happily agree. However, in this case, the Status objects are
static and never supposed to change (without reloading the entire project).
Based on this assumption, all that I want is a constant `MAX_ID` that reflects
the largest possible ID of the existing Status objects, so that frequent access
to it does not each time inflict a database access.
Therefore, my older code just had a module global variable like this:
MAX_ID = Status.objects.aggregate(Max('id'))['id__max']
This is simple and "usually" works well, but note that it fails whenever an
empty database is initialized, that is, whenever the very first migration is run
(in which case the above global code is run even before the Status table
exists), which in turn happens when the project is deployed to a new site or
whenever the test database is populated.
In summary:
Code that is run at load time (such as the global `MAX_ID = ...` above) or close
to load time (such as the Django system checks) cannot access the database if
the database is only populated at a later time, as is the case with initial
migrations for new deployments or tests databases.
What I would like to check, though, is the production or development databases;
thus my question for marking the model check „for deployment only“.
Best regards,
Carsten
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