This is heads up in case anyone sees something similar:
I have managed to trigger this degenerate query case in two completely
different Django 2.2 projects. In production with a normal sized dataset,
the query time is fine. But during unit testing with a small subset of the
data, the queries took a long time. A LONG time.
In the most recent case each query took 100x longer. 200+ seconds instead
of 2 seconds. The unit test dataset isn't very large because it's a unit
test.
I think I may have first seen this when I upgraded the project to postgres
11.
Manually vacuuming between tests resolves the issue. (Yes, autovacuum is
on by default -- and isn't the db created from scratch for each 'manage
test' invocation?)
This is how I did it:
def _vacuum():
# Some unit test queries seem to take a much longer time.
# Let's try vacuuming.
# https://stackoverflow.com/a/13955271/2077386
with connection.cursor() as cursor:
logger.info("Vacuum: begin")
cursor.execute("VACUUM ANALYZE")
logger.info("Vacuum: complete")
class VacuumMixin:
@classmethod
def setUpClass(cls):
_vacuum()
return super().setUpClass()
@classmethod
def tearDownClass(cls):
ret = super().tearDownClass()
_vacuum()
return ret
If anyone else sees this, please let me know. Maybe we can further RCA it.
--
You received this message because you are subscribed to the Google Groups
"Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to django-users+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-users/e76b105e-ed53-4031-869c-830f94677ef4n%40googlegroups.com.
