#33901: non-deterministic collations doesn't work with Unique=True on
Postgres13.3
-------------------------------------+-------------------------------------
Reporter: Ed Chai | Owner: Ed Chai
Type: Bug | Status: closed
Component: Migrations | Version: dev
Severity: Normal | Resolution: fixed
Keywords: collation unique | Triage Stage: Ready for
citext | checkin
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Petter Friberg):
Not sure if there should be a new ticket here or not but I'm still seeing
this on 4.2 when having a relation that points to a unique field with a
non-deterministic collation.
For instance, consider if we run the following migration operation:
{{{
#!python
migrations.CreateModel(
name="ExtendedUser",
fields=[
('id', models.BigAutoField(auto_created=True, primary_key=True,
serialize=False, verbose_name='ID')),
('user',
models.OneToOneField(on_delete=django.db.models.deletion.CASCADE,
to=settings.AUTH_USER_MODEL, to_field='username'))
]
)
}}}
Running `manage.py sqlmigrate` for that operation displays the generated
`_like` index
{{{
#!sql
CREATE INDEX "myapp_extendeduser_user_id_<chars>_like" ON
"myapp_extendeduser" ("user_id" varchar_pattern_ops);
}}}
(Not sure if there's more to it but) I think the
[https://code.djangoproject.com/changeset/f3f9d03edf17ccfa17263c7efa0b1350d1ac9278
provided patch] could be extended with something like below to resolve at
least `OneToOneField`
{{{
#!python
# Non-deterministic collations on Postgresql don't support
indexes
# for operator classes varchar_pattern_ops/text_pattern_ops.
if getattr(field, "db_collation", None) or (field.is_relation
and getattr(field.target_field, "db_collation", None)):
return None
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/33901#comment:13>
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