Database "execute hooks" for instrumentation

[Shai Berger]

Quoting, editing and summarizing ​a 5-month old thread from django-developers:

Add the ability to install general instrumentation hooks around the database execute() and executemany() calls.

Such hooks would allow all sorts of interesting features. For one, they could replace the current special-case allowing assertNumQueries() & friends to record queries out of debug mode (it's an ugly hack, really), but they could also support other use cases:

• Prevent database access during execution of render() calls and serialization, to make sure all database access is being done explicitly in the view.
• Preventing database access during tests unless specifically requested by the test (per @carljm, pytest-django does this, currently via monkeypatching).
• Listen in on all executed queries for performance analysis (per @adamchainz, django-perf-rec currently monkey patches connection.ops.last_executed_query to achieve this)

[Shai Berger]

(I was a little confused about the meaning of the "needs tests" and "needs docs" flags)

[Tim Graham <timograham@…>]

In d612026c:

Refs #28595 -- Added a hook to add execute wrappers for database queries.

Thanks Adam Johnson, Carl Meyer, Anssi Kääriäinen, Mariusz Felisiak,
Michael Manfre, and Tim Graham for discussion and review.

[Raphael Gaschignard]

I might be missing something here, so I am not changing the state myself. But I believe this instrumentation has been successfully added in 2.0? As found at ​https://docs.djangoproject.com/en/2.2/topics/db/instrumentation/

[Adam Johnson]

Thanks Raphael, yes this feature was merged in 2.0, the ticket was just left in limbo as open. Closing now.