#34964: Reversing the order of Q objects in a CheckConstraint generates a
migration
-------------------------------------+-------------------------------------
Reporter: Jacob Walls | Owner: Jacob
Type: | Walls
Cleanup/optimization | Status: assigned
Component: Migrations | Version: dev
Severity: Normal | Resolution:
Keywords: noop | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Jacob Walls):
Thanks for the extra context around those edge cases. I'd love to know
more about them so I can look for them in my own projects.
I notice we've been sorting the arguments to the Q constructor since
#29125. So if someone did need to change the order to work around a
database edge case, they'd ''want'' a change from `Q(A, B)` to `Q(A) &
Q(B)` to generate a migration, since if B sorts before A, it can only be
expressed in Django as the latter, and this PR would take away the
migration to make it.
The argument in favor of this change (which is very slight, I know) is
that refactoring the code for consistency/readability with the surrounding
constraints might generate a migration with a table rebuild. That's
something you might miss. In other words, you need to know that it's not
worth paying that cost when you're editing/reviewing the code. Until I
knew about these edge cases, I thought that was a potential DX win to
reduce cognitive burden.
Finally, I guess if we still wanted this change we might ought to block it
on a resolution of #25245. Should we Someday/Maybe this ticket, then?
--
Ticket URL: <https://code.djangoproject.com/ticket/34964#comment:9>
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