I two comments, and as always Your Milage May Vary.
- I wonder if you have the right indexes on your Postgres database? The
previous people report much faster completion times for test that use
Postgres as the database. Perhaps your domain is just hard (and you
description makes it sound that way), but "Explain Plan" might be your best
friend here.
- Sqlite does not enforce length limit constraints on text fields. You
can declare a field to be CharField(max_length=200), and Sqlite will
happily put a longer string into the field. Postgres will not.
This came up when I was importing data from an older generation of our
product. My custom import code ran successfully against Sqlite and the
exact same command failed against Postgres.
- (And yes, I said only two points. But this just occurs to me...)
Can you divide your test suite into distinct independent chunks, and run
them in parallel? Either against one common database or using one database
per test-chunk?
On Friday, September 14, 2018 at 11:32:49 AM UTC-4, Hezi Halpert wrote:
>
> I would like to share with you an issue we encounter while moving from
> sqlite to postgres with heavily use of Django testing.
>
> We have Django app with ~700 tests. Most of them accessing database. We
> recently migrated the database from sqlite to postgres.
> Many of our tests were written in a way that compares actual pk’s
> (hard-coded pks or just file/json comparisons) . Since Django testing on
> sqlite (testcases.TestCase class) creates in-memory database (which is
> being reseted every unit test by default), we never had a problem with it.
> However, Django TestCase on postgres create completely another test db
> which preserves the pk sequences between different tests. And since many of
> our tests were written in a way that compares actual pk’s they all start
> fail - depends on the exact tests execution order.
> Even tests which expect some pk and are were not failed yet, can
> potentially failed in the future - depends on adding/editing other tests
> which may change the db sequence
>
> We consider the following solutions:
>
> 1. Move to TransactionTestCase (instead of TestCase) and use
> “reset_sequences = True” flag. Cons: TransactionTestCase reduces
> performance dramatically (~4 times longer in some of the tests)
> 2. Refactor all failed tests: remove all hard-coded references to the
> pk. Cons: Require much Dev effort (we had more then 70 such tests)
> 3. Route the database in settings.py such it will use sqlite instead
> of postgres when running tests. Cons: It will not actually test the real
> scenarios - not an option
> 4. Combine reset_sequences flag with TestCase in our own version to
> TestCase: OurTestCase class and make everything to inherit from it. This
> is
> the option we finally decided of. See below.
>
>
> from django.test import TestCase, testcases
>
>
> class OurTestCase(TestCase):
> reset_sequences = True
>
> def _fixture_setup(self):
> for db_name in self._databases_names(include_mirrors=False):
> if self.reset_sequences:
> self._reset_sequences(db_name)
> if self.fixtures:
> call_command('loaddata', *self.fixtures, **{'verbosity': 0,
> 'database': db_name})
> if not testcases.connections_support_transactions():
> self.setUpTestData()
> return super(TestCase, self)._fixture_setup()
> self.atomics = self._enter_atomics()
>
>
> Another problem of these kind of tests is the default ordering assumption
> of Django which changes significantly between postgres and sqlite when
> testing.
> Therefore, models included in such tests must have a hint for Django
> regarding the default ordering retrieval.
> Our solution was to make all models inherit from DexterModelDefaultOrder
> (below)
>
>
> class DexterModelDefaultOrder(models.Model):
> class Meta:
> abstract = True
> ordering = ['id']
>
>
>
> I hope it (will) help someone
>
>
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