#23091: Squashed migrations may try to add existing constraint if there was
RunPython between create and alter some-model migrations
-------------------------------+----------------------
Reporter: anonymous | Owner: nobody
Type: Uncategorized | Status: new
Component: Migrations | Version: 1.7-rc-1
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------+----------------------
I squashed a lot of migrations, some with RunPython functions. The
squashed migration needed some fixing to work. At some point of the
squashed migration there was a "CreateModel" operation that created some
model with relation to User:
{{{
('user', models.ForeignKey(blank=True, to_field='id',
to=settings.AUTH_USER_MODEL, null=True)),
}}}
But as the models got edited there was a migration (rather pointless,
caused by editable=False):
{{{
field=models.ForeignKey(blank=True, null=True, to_field='id',
to=settings.AUTH_USER_MODEL, editable=False),
}}}
In between there was a RunPython which quite likely prevented squashing
those two migrations into one. Running such migrations ended up with:
{{{
File "/var/www/buku/virtualenvs/1405079302/lib/python3.4/site-
packages/django/db/backends/utils.py", line 66, in execute
return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: constraint
"buku_vendor_offerredir_user_id_75e4400f46095260_fk_auth_user_id" for
relation "buku_vendor_offerredirect" already exists
}}}
The SQL it was trying to run was:
{{{
ALTER TABLE "buku_vendor_offerredirect" ADD CONSTRAINT
buku_vendor_offerredir_user_id_75e4400f46095260_fk_auth_user_id FOREIGN
KEY ("user_id") REFERENCES "auth_user" ("id") DEFERRABLE INITIALLY
DEFERRED []
}}}
It would be handy if that "self.cursor.execute(sql, params)" from
django/db/backends/utils.py also printed the SQL it was trying to run so
it would be easier to find the operation in migration (or make exception
more verbose).
I had like 4 such cases. Some quite serious like removing null=True and
adding unique=True
--
Ticket URL: <https://code.djangoproject.com/ticket/23091>
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