#31732: Cache function signatures
-------------------------------------------------+------------------------
Reporter: Adam (Chainz) Johnson | Owner: nobody
Type: Cleanup/optimization | Status: new
Component: Utilities | Version: master
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 |
-------------------------------------------------+------------------------
I found a bit of a performance regression in Django 2.1 and 2.2, gone in
3.0. There, `SQLCompiler.get_converters()` ran `func_supports_parameter()`
for every field converter
Unfortunately the information isn't cached and `inspect.signature()` isn't
particularly fast.
Using py-spy on a client test suite, I found `func_supports_parameter()`
taking 0.25% of the total run time. This isn't much absolutely, but it was
reachable only through pathways using `Query.get_aggregation()` (2.1%) and
`Query.get_count()` (0.63%). So from those paths,
`func_supports_parameter()` took 0.25 / (2.1 + .63) = ~10% of the time to
execute aggregates, for easily cached information.
Given that function objects are immutable, I think all the use of
`inspect.signature` in `django.utils.inspect` could go through a wrapper
that caches with a `WeakKeyDictionary` or `functools.lru_cache` to avoid
re-inspecting the same signatures.
It doesn't look like there is any usage of those functions in hot paths in
Django 3.0+ but it could be useful to have this protection for any future
function argument deprecations.
--
Ticket URL: <https://code.djangoproject.com/ticket/31732>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-updates/053.ba19d7686458a982264fef8d2a98f306%40djangoproject.com.
