Different query counts under Oracle when savepoints are involved

[Aymeric Augustin]

This is a follow-up on #20387, see comments 5 and 6.

In short, Oracle doesn't have RELEASE SAVEPOINT, which means transaction.commit_savepoint() doesn't do anything. As a consequence, connection.queries contains one less entry under Oracle than under other databases.

#20387 was fixed by hardcoding the difference into the tests. This ticket is about finding a more robust solution to the general problem.

[Aymeric Augustin]

I'm leaning towards stealing the hack Michael Manfre used in django-mssql: ​https://bitbucket.org/Manfre/django-mssql/src/a2caadaef0ba97faa091dbfe61fe4c04d1e84188/sqlserver_ado/base.py?at=default#cl-345

Pull request: ​https://github.com/django/django/pull/2777

[Aymeric Augustin <aymeric.augustin@…>]

In 40bfd8561d016f6632c95d03e46a720571ad1a8a:

Fixed #20420 -- Normalized query counts on Oracle.

This is achieved by inserting a fake entry in connection.queries when
not releasing a savepoint (since Oracle doesn't support that operation.)

Also removed the can_release_savepoints feature that was recently added,
but is superseded by this solution.

[Aymeric Augustin <aymeric.augustin@…>]

In 5cde9a7018021fc3c005e4ebcfa63967bcf56285:

[1.7.x] Fixed #20420 -- Normalized query counts on Oracle.

This is achieved by inserting a fake entry in connection.queries when
not releasing a savepoint (since Oracle doesn't support that operation.)

Also removed the can_release_savepoints feature that was recently added,
but is superseded by this solution.

Backport of 40bfd856 from master.

[Tim Graham <timograham@…>]

In 84714dfed726212122ac9a143ddbe6719dac5884:

[1.7.x] Fixed test failures due to refs #20420.

cfcca7ccce3dc527d16757ff6dc978e50c4a2e61 renamed connection.queries
to queries_log and this wasn't backported to stable/1.7.x.