#29790: Release notes / Changelog missing information about change in duplicate
pk
behaviour in 2.1
-------------------------------------+-------------------------------------
Reporter: He3lixxx | Owner: nobody
Type: Bug | Status: new
Component: | Version: 2.1
Documentation | Keywords: multiple primary
Severity: Normal | keys migration id uuid
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
We migrated a model from a AutoField as id (default behaviour) to a
UUIDField in the past, using a migration that looked like this with django
2.0:
https://code.djangoproject.com/ticket/28541
There was a bug in SQLite though, which as of today only has the
workaround listed in the bug tracker:
https://code.djangoproject.com/ticket/28541
Thus, we ended up writing our migration like this: https://github.com/fsr-
itse/EvaP/blob/master/evap/evaluation/migrations/0062_replace_textanswer_id_with_uuid.py
When we try updating to django 2.1 now, this migration fails whenever you
call migrate with the error
{{{django.db.utils.ProgrammingError: multiple primary keys for table
"evaluation_textanswer" are not allowed}}}
It works if we add a RemoveField instruction for the old id before setting
{{{primary_key=True}}} on the new UUIDField. But this will trigger the
SQLite bug listed above. Changing the old AutoField to
{{{primary_key=False}}} where the RemoveField instruction would be doesn't
fix the error.
The documentation states that a object may not have more than one primary
key here:
https://docs.djangoproject.com/en/2.0/ref/models/fields/#django.db.models.Field.primary_key
Still, in the release notes for django 2.1 it should be noted that
django's behaviour was changed here. Also, I would appreciate if there was
some kind of documentation on how you should migrate primary keys from a
field to another if no two primary keys are allowed in between. There
should be a way without squashing the migrations as we want to keep the
history.
--
Ticket URL: <https://code.djangoproject.com/ticket/29790>
Django <https://code.djangoproject.com/>
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