#23740: Cannot drop unique_together constraint on a single field with its own
unique=True constraint
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Reporter: lanzz | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.7
Severity: Normal | Resolution:
Keywords: unique_together | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by jdavisp3):
Replying to [comment:5 matthewwestcott]:
> Can't see a good way of fixing this without breaking backwards
compatibility. The alter_unique_together logic in db/backends/schema.py
relies on the UNIQUE constraints generated by unique_together to be
distinguishable within the database from constraints generated through
other mechanisms (e.g. unique=True) - but this isn't possible when the
unique_together rule only contains a single field.
I have encountered this same issue. Could you explain the backwards
compatibility issue here? It seems to me that the bug is in attempting to
drop or create an index when that is not called for, either because the
index is required by a different constraint or was already created by
another constraint. Is that behavior that needs to be kept.
--
Ticket URL: <https://code.djangoproject.com/ticket/23740#comment:6>
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