Opened 8 years ago
Last modified 8 years ago
#28272 closed Bug
PostgreSQL: AutoField sequences don't increment when inserting objects with an explicitely specified PK — at Version 1
Reported by: | François Freitag | Owned by: | nobody |
---|---|---|---|
Component: | Database layer (models, ORM) | Version: | dev |
Severity: | Normal | Keywords: | postgresql sequence |
Cc: | Mariusz Felisiak | Triage Stage: | Unreviewed |
Has patch: | no | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description (last modified by )
Developers are allowed to specify primary keys for newly created python instances [1]. However, on PostgreSQL, the sequence attached to the serial is not updated to take manually set PKs into account.
The following queries fail on PostgreSQL:
CREATE TABLE foo (id serial primary key, bar text); INSERT INTO foo VALUES (1, 'thing'); INSERT INTO foo (bar) VALUES ('other'); -- ERROR: duplicate key value violates unique constraint "foo_pkey" -- DETAIL: Key (id)=(1) already exists.
Hence, the following test case fails in Django:
# Using models from tests/bulk_create/models.py def test_create_explicit_pk(self): Country.objects.create(name='France', iso_two_letter='FR') next_pk = Country.objects.latest('pk').pk + 1 Country.objects.create(pk=next_pk, name='US', iso_two_letter='US') Country.objects.create(name='NL', iso_two_letter='NL') # FAILS because next_pk is already in use. # The sequence should have yielded next_pk + 1
In my opinion, the sequence attached to the primary key should be manually set to the next available PK after inserting an object with an explicitly specified PK (e.g. using setval [2]). The same issue can be observed for bulk_create
, where I think the highest primary key of the batch should be used to determine the next value in the DB sequence.
MariaDB [3] and SQLite [4] update the next value in the sequence when autoincrement is used.
Oracle might be also be affected by this issue. I was able to find this old ticket on the bug tracker[5].
[1] https://docs.djangoproject.com/en/dev/ref/models/instances/#explicitly-specifying-auto-primary-key-values
[2] https://www.postgresql.org/docs/current/static/functions-sequence.html
[3] https://mariadb.com/kb/en/mariadb/auto_increment/#setting-explicit-values
[4] https://sqlite.org/autoinc.html
[5] https://code.djangoproject.com/ticket/6598