#34456: Add a way to set allow_cascade=True in _fixture_teardown()
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               Reporter:  devanubis          |          Owner:  nobody
                   Type:  Uncategorized      |         Status:  new
              Component:  Testing framework  |        Version:  4.2
               Severity:  Normal             |       Keywords:
           Triage Stage:  Unreviewed         |      Has patch:  0
    Needs documentation:  0                  |    Needs tests:  0
Patch needs improvement:  0                  |  Easy pickings:  0
                  UI/UX:  0                  |
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 We use [django-timescaledb](https://github.com/schlunsen/django-
 timescaledb) as our database backend and ran into a problem with some of
 our tests for django migrations on tables using timescale compression.

 I [wrote up our problem on `django-timescaledb` back in
 October](https://github.com/schlunsen/django-timescaledb/issues/40), but
 it essentially boils down to:

 * `django.test.testcases.TransactionTestCase._fixture_teardown()` calls
 `django.db.backends.postgresql.operations.sql_flush()` and truncates every
 table at the end of tests.
 * In timescaledb, compressed hypertables create "chunks" as tables with a
 subset of the hypertable's data.
 * Because we have foreign keys in some of our hypertables, the chunk
 tables also get that foreign-key rule.
 * Those chunk tables are transparent to Django, and so are not in the list
 to be truncated.
 * And so, the truncation fails, because the chunk tables still reference
 some of the data being truncated.

 The easiest solution seems to be to allow `_fixture_teardown()` to opt-in
 to setting `allow_cascade=True` when truncating.

 We're happy to submit a PR if this proposal gets accepted.

-- 
Ticket URL: <https://code.djangoproject.com/ticket/34456>
Django <https://code.djangoproject.com/>
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