Opened 16 months ago
Closed 16 months ago
#34729 closed New feature (wontfix)
Add explicit option to enable IF EXISTS / IF NOT EXISTS in PostgresQL index operations
Reported by: | Laurent Tramoy | Owned by: | |
---|---|---|---|
Component: | contrib.postgres | Version: | 4.2 |
Severity: | Normal | Keywords: | |
Cc: | Triage Stage: | Unreviewed | |
Has patch: | no | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description
Hello,
I'd like to be able to add a IF NOT EXISTS
clause when creating indexes (both with AddIndex and AddIndexConcurrently).
I've read this ticket https://code.djangoproject.com/ticket/34298 where Mariusz considers it's a bad idea (for constraints), and I get his point, however I've a few counter arguments:
- I feel like the workflow "add an index in a deployed environment / check it works as expected / add it to Django code" is quite common in "real-life" applications, for now we have to write a custom
SeparateDatabaseAndState
each time we do this - The idea would be to enable this explicitly (either by adding a
AddIndexIfNotExists
operation, or by adding a parameter toAddIndex
/AddIndexConcurrently
), so people should know what they're doing when using this. - The
IF EXISTS
clause is already used when dropping the index, it would be more consistent to be able to allow it when adding the index too https://github.com/django/django/blob/afc880571d5f5a16b977070b15014f9583524898/django/db/backends/postgresql/schema.py#L25
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I still think it is a bad idea for exactly the same reasons I already mentioned in the #34298. Also, I don't think that separate operations or extra arguments to control this behavior is a good idea, following this path we could add the same to all migration operations. Why should index creation be treated differently? Last but not least this syntax is not supported by all database engines with built-in backends.
Please first start a discussion on the DevelopersMailingList, where you'll reach a wider audience and see what other think, and [https://docs.djangoproject.com/en/stable/internals/contributing/triaging-tickets/#closing-tickets follow the triaging guidelines with regards to wontfix tickets.