#30375: Use "NO KEY" when doing select_for_update for PostgreSQL -------------------------------------+------------------------------------- Reporter: Manuel Weitzman | Owner: nobody Type: | Status: new Cleanup/optimization | Component: Database layer | Version: master (models, ORM) | Severity: Normal | Resolution: Keywords: postgres, lock, | Triage Stage: database, operation | Unreviewed Has patch: 1 | Needs documentation: 0 Needs tests: 0 | Patch needs improvement: 0 Easy pickings: 0 | UI/UX: 0 -------------------------------------+-------------------------------------
Comment (by Manuel Weitzman): Replying to [comment:2 Simon Charette]: > > ... in Django, primary key fields are read-only, so locking them makes no sense > > That's not true AFAIK. Even if `AutoField` are backed by sequences and generated on the database side they can still be overridden by developers. Same thing with non-`AutoField` primary keys (e.g. `UUIDField(default=uuid.uuid4)`). Then the docs are wrong or at least misleading: ''"The primary key field is read-only. If you change the value of the primary key on an existing object and then save it, a new object will be created alongside the old one."" (https://docs.djangoproject.com/en/2.2/topics/db/models/) Which means that UPDATEs over PKs are transformed into INSERTs > On the other hand updating a primary key while holding a lock is really uncommon so I wouldn't be against adding a `select_for_udate(primary_key)` parameter that defaults to `False`. We just have to make sure that we still allow these operations to be performed somehow. That is possible, I tested today and only a few changes are required to achieve this behavior. Maybe I could send a PR soon for review? -- Ticket URL: <https://code.djangoproject.com/ticket/30375#comment:3> 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 django-updates+unsubscr...@googlegroups.com. To post to this group, send email to django-updates@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-updates/064.783c6ff1398863c7349397b7c7af8e4e%40djangoproject.com. For more options, visit https://groups.google.com/d/optout.