Document that SQL logging does not include "framework level" queries

[Brian May]

As discussed here ​https://docs.djangoproject.com/en/dev/topics/logging/ django supports logging of raw SQL queries. "For example, every SQL statement executed by a request is logged at the DEBUG level to this logger."

However, at least for mysql, this doesn't include initialization or session management SQL queries.

Using wireshark I see a number of extra queries, that are never logged, like:

SET NAMES utf8
set autocommit=0
SET SQL_AUTO_IS_NULL = 0
set autocommit=1
set autocommit=0
rollback
set autocommit=1

I assume "commit" is also on this list, however not part of this test.

Being able to see all the queries is important in order to debug obscure problems.

Thanks

[Tim Graham]

I think for most use cases this would just add more noise to the logs. You can always turn on query logging at the database level if you need it. I'll leave this open for a second opinion and perhaps we can make a documentation update to note this limitation if we don't change the behavior.

[Aymeric Augustin]

In my opinion, the SQL logger aims at providing "application-level" debugging. It answers the question "what queries does my application emit?". The queries you're mentionning are "framework-level". If your question is "what queries does my database receive?", like Tim, I suggest turning on the database's query logging.

[Tim Graham <timograham@…>]

In 4d8d76e7a89858932b6f4f280a0ebf4cf94ab4b7:

Fixed #21484 -- Documented that SQL logging does not include "framework level" queries.

[Tim Graham <timograham@…>]

In a228545026e30d3223b3fbb13a262b5e005101ae:

[1.6.x] Fixed #21484 -- Documented that SQL logging does not include "framework level" queries.

Backport of 4d8d76e7a8 from master