Slowdown of pytest collection in sqlalchemy in python 3.9+

• a detailed description of the bug or problem you are having
• output of pip list from the virtual environment you are using
• pytest and operating system versions
• minimal example if possible

We noticed that from python 3.9 pytest takes a significantly more time (~4x) to collect the tests for sqlalchemy. You can run the following docker to compare. python 3.7 and 3.8 are ok (not fast not slow), python 3.9 and 3.10 are noticeably slower

docker run -ti --name py --rm python:3.7 bash -c 'git clone https://github.com/sqlalchemy/sqlalchemy.git --depth 100; pip install pytest; cd sqlalchemy; time pytest --collect-only'
docker run -ti --name py --rm python:3.8 bash -c 'git clone https://github.com/sqlalchemy/sqlalchemy.git --depth 100; pip install pytest; cd sqlalchemy; time pytest --collect-only'
docker run -ti --name py --rm python:3.9 bash -c 'git clone https://github.com/sqlalchemy/sqlalchemy.git --depth 100; pip install pytest; cd sqlalchemy; time pytest --collect-only'
docker run -ti --name py --rm python:3.10 bash -c 'git clone https://github.com/sqlalchemy/sqlalchemy.git --depth 100; pip install pytest; cd sqlalchemy; time pytest --collect-only'

the times on my pc are as floows:

#py37
real    0m27.949s
user    0m26.717s
sys     0m1.220s
#py38
real    0m27.952s
user    0m26.893s
sys     0m1.050s
# py39
real    1m45.581s
user    1m42.574s
sys     0m2.990s
# py310
real    1m46.255s
user    1m43.648s
sys     0m2.590s

cc @zzzeek

[CaselIT]

Ok, I had to use hookwrapper in pytest_runtest_teardown since that finalizer needs to run after all the class fixture ones, but it seems to be working,

The last version is on gerrit https://gerrit.sqlalchemy.org/c/sqlalchemy/sqlalchemy/+/3332

edit, yes the test all pass.

Having the previous behaviour of addfinalizer would be nice to have, but I think this can be closed. Thanks a lot for all the support and help!

[nicoddemus]

alternatively is there an approximate date you are aiming towards for v7?

We are planning a release candidate pretty soon, likely within the week, so shouldn’t be far.

We also tripping an assert while adding a finalizer

The traceback shows get_test_class_from_fn, does that function return pytest.Class both in v6 and v7? If so things should just work, you should be able to attach finalizers to classes.

are are trying to add it in pytest_runtest_setup here

I don’t see get_test_class_from_fn in the link, was that removed afterwards?

Ahh I see it in Gerrit. You actually don’t need that function, item.getparent(pytest.Class) will return the class for that item, or None in case it doesn’t have a class (it is a free function). And this will work in v6 and v7.

Same is valid for other places like this:

    items[:] = sorted(
        newitems,
        key=lambda item: (
            get_test_class_from_fn(item).parent.name,
            get_test_class_from_fn(item).name,
            item.name,
        ),
    )

Which can be written as:

    items[:] = sorted(
        newitems,
        key=lambda item: (
            item.getparent(pytest.Module).name,
            item.getparent(pytest.Class).name,
            item.name,
        ),
    )

item.getparent(pytest.Module) will always return a pytest.Module of course.