#36779: DeleteModel can lead to missing FK constraints
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Reporter: Jamie Cockburn | Owner: Vishy Algo
Type: Bug | Status: assigned
Component: Migrations | Version: 6.0
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1
Easy pickings: 0 | UI/UX: 0
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Changes (by Simon Charette):
* cc: Simon Charette (added)
Comment:
I'm not against a feature flag at all if we have a use for it but I can't
reproduce the test failures you are alluding to by running the full SQLite
test suite and it seems to be a propery required by third party backends
to pass the full schema and migrations test suites.
Given `sqlite3.DatabaseSchemaEditor.delete_model` completely ignores the
`cascade` argument by when calling
`base.DatabaseSchemaEditor.delete_model` though `super()` in the proposed
patch and that only the later makes use of `sql_delete_table_cascade` I
don't see how any code path can issue a `DROP TABLE {table} CASCADE` on
SQLite.
> This approach ensures the API is extensible and backward-compatible
without breaking SQLite or third-party backends.
Could you elaborate on what you mean by that? SQLite doesn't seem to be
broken here (as pointed out above) and the default on all other core
backends use to be to cascade by default (Oracle, Postgres, MySQL). All we
did here is to change the default of `DropModel` to not cascade and allow
the schema editor to take a more informed decision.
Given the usage and expectations that `cascade=True` is implemented to get
the schema and migrations test suite passing I don't see how
`supports_table_drop_cascade = False` would be useful; third-party
database backends must emulate it even if they don't support it natively.
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Ticket URL: <https://code.djangoproject.com/ticket/36779#comment:9>
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