Fix cursor_factory re-wrapping with connection pooling

[karalarmehmet]

• Fix severe performance degradation when using Django's PostgreSQL connection pooling (pool: True) with django-prometheus
• Move cursor_factory wrapping from get_new_connection() to get_connection_params() in both postgresql and postgis backends
• Fix postgis backend using hardcoded "postgis" alias instead of self.alias

Closes: #445

[karalarmehmet]

@asherf I would appreciate your review in your spare time 👍

[Copilot]

Pull request overview

This PR fixes a severe performance regression (issue #445) when using django-prometheus with Django 5.1's new PostgreSQL connection pooling. With connection pooling, connections are reused from a pool, but the old code was re-wrapping the cursor_factory in get_new_connection() on every connection reuse. This caused the class's __mro__ to grow unboundedly, degrading performance significantly with each request. The fix moves the cursor_factory wrapping from get_new_connection() to get_connection_params(), which is called once at pool creation time. It also fixes a pre-existing bug in the PostGIS backend where the alias was hardcoded as "postgis" instead of using self.alias.

Changes:

• Move cursor_factory wrapping from get_new_connection() to get_connection_params() in both the PostgreSQL and PostGIS backends
• Fix PostGIS backend using hardcoded "postgis" alias instead of self.alias
• Add unit tests for the new get_connection_params() behavior in test_db_wrapper.py

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
django_prometheus/db/backends/postgresql/base.py	Moves cursor_factory wrapping to get_connection_params()
django_prometheus/db/backends/postgis/base.py	Same fix as postgresql; also corrects hardcoded "postgis" alias to self.alias
django_prometheus/tests/test_db_wrapper.py	New unit test file covering the wrapping behavior and the no-re-wrap guarantee

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[karalarmehmet]

@asherf Fixed the reason for test failures 👍

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

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[karalarmehmet]

@asherf Thanks for your time I checked Copilot review suggestions and responded inline with the reasons why they don't apply You can check them 👍