#23740: Cannot drop unique_together constraint on a single field with its own
unique=True constraint
---------------------------------+------------------------------------
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
---------------------------------+------------------------------------
Comment (by 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.
Another way this manifests itself is to perform the following steps, in
separate migrations:
* create a model
* add unique=True to one if its fields
* add a unique_together constraint for that same field
This results in two identical calls to _create_unique_sql, leading to a
'relation "foo_bar_name_1e64ed8ec8cfa1c7_uniq" already exists' error.
--
Ticket URL: <https://code.djangoproject.com/ticket/23740#comment:5>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-updates/063.c39a21255137485a0a27923cbd25f683%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.
