#28832: django migrations to PostgreSQL not handling order_with_respect_to
removals
-------------------------------------+-------------------------------------
Reporter: AJ | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.11
Severity: Normal | Resolution:
Keywords: | Triage Stage:
order_with_respect_to PostgreSQL | Unreviewed
makemigrations |
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Simon Charette):
Is it possible that you encountered the PostgreSQL constraint violation
for the short period of time where your new code that removed the
`order_with_respect_to` was deployed to your web workers while you had not
run your migration that removed the `_order` column?
The only way to achieve zero-downtime for this kind of operation would be
to perform the following manipulations:
1. Run a migration that makes `_order` nullable.
2. Deploy the code removing the `order_with_respect_to` to your workers.
3. Run a migration that drops the `_order` column.
It's really not different from the manipulations required for removing a
normal non-nullable field. The `AlterOrderWithRespectTo` operation is
harder to reason about because it doesn't make it clear it's implemented
using an hidden `_order` field that requires the same care.
--
Ticket URL: <https://code.djangoproject.com/ticket/28832#comment:3>
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