#31881: Raise Index name limit for postgres
-------------------------------------+-------------------------------------
Reporter: Jarek Glowacki | Owner: nobody
Type: | Status: closed
Cleanup/optimization |
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution: needsinfo
Keywords: postgres index | Triage Stage:
max_name_length | Unreviewed
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 Jarek Glowacki):
Hey sorry for the slow response.
Replying to [comment:1 felixxm]:
> This will break backwards compatibility for `PostgresIndex` subclasses
with long suffixes, because currently we allow suffixes of any length.
I had a deeper dig and I don't see how that's the case.. `max_name_length`
is ''only'' interrogated when:
- an index name has been automatically constructed:
https://github.com/django/django/blob/8c7992f658e1125f8dc20b19206e8bbbe4187372/django/db/models/indexes.py#L118-L121
- system checks run:
https://github.com/django/django/blob/8c7992f658e1125f8dc20b19206e8bbbe4187372/django/db/models/base.py#L1604-L1612
The code that automatically generates indexes would remain untouched, and
unaffected:
https://github.com/django/django/blob/8c7992f658e1125f8dc20b19206e8bbbe4187372/django/db/models/indexes.py#L110-L117
It could potentially be relaxed to pad out the hash up to
`MyIndex.max_name_length`, but I'm not suggesting we change this, and I
don't think doing so would provide any benefit.
I've gone ahead and implemented the change here:
https://github.com/django/django/compare/master...jarekwg:ticket_31881?expand=1
Please note that `PostgresIndex` isn't used by default for Postgres
backends, it's only used when inherited by those special Postgres-specific
Indexes. So the solution I'm suggesting would only help in cases where
users explicitly specify `PostgresIndex` when defining their custom
Indexes. Users with custom overrides would still be overriding all this,
so I don't see how they'd run into regressions.
The only hardcoded shenanigans i could find that would have trouble if
suffix length were to change is the one here, but it's oracle-specific
code, so wouldn't be affected by our work anyway:
https://github.com/django/django/blob/8c7992f658e1125f8dc20b19206e8bbbe4187372/django/db/backends/oracle/operations.py#L596
All that said, I agree that documenting `suffix` and `max_name_length`
would also be quite helpful. I wouldn't've opened this ticket had there
been a note in the docs, instructing me to create my own index class with
these attributes. I'm happy to offer a PR for that too.
--
Ticket URL: <https://code.djangoproject.com/ticket/31881#comment:3>
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