The ORM didn't reuse joins for direct foreign key traversals when using
chained filters. For example:
qs.filter(fk__somefield=1).filter(fk__somefield=2))
produced two joins.
As a bonus, reverse onetoone filters can now reuse joins correctly
The regression was caused by the join() method refactor in commit
68847135bc
Thanks for Simon Charette for spotting some issues with the first draft
of the patch.
This is necessary because get_model() checks are case insensitive, and if the swapable check isn't, the
swappable logic gets tied up in knots with models that are partially swapped out.
Thanks to chris@cogdon.org for the report and extensive analysis, and Preston for his work on the draft patch.
Cleaned up the implementation of base convert_values() a little, and
made sure it accepts None as a value for numeric fields.
There are no tests attached. The reason is that not all of the
convert_values() accept None as a value for numeric fields (for example
sqlite3.convert_values()).
The reason the base convert_values() needs to accept None is that this
situation might arise in custom compilers for 3rd party backends. It
is easy to keep the convert_values() working, so lets do that.
This is a rather large refactoring. The "lookup traversal" code was
splitted out from the setup_joins. There is now names_to_path() method
which does the lookup traveling, the actual work of setup_joins() is
calling names_to_path() and then adding the joins found into the query.
As a side effect it was possible to remove the "process_extra"
functionality used by genric relations. This never worked for left
joins. Now the extra restriction is appended directly to the join
condition instead of the where clause.
To generate the extra condition we need to have the join field
available in the compiler. This has the side-effect that we need more
ugly code in Query.__getstate__ and __setstate__ as Field objects
aren't pickleable.
The join trimming code got a big change - now we trim all direct joins
and never trim reverse joins. This also fixes the problem in #10790
which was join trimming in null filter cases.
The trim argument was used by split_exclude() only to trim the last
join from the given lookup. It is cleaner to just trim the last part
from the lookup in split_exclude() directly so that there is no need
to burden add_filter() with the logic needed for only split_exclude().
This makes it easier to make a ModelBackend-compliant (with regards to
permissions) User model.
Thanks to cdestigter for the report about the relationship between
ModelBackend and permissions, and to the many users on django-dev that
contributed to the discussion about mixins.
This documents the behavior introduced by cc337a74, which is BACKWARDS
INCOMPATIBLE for any attempt to invoke a method on a manager using the
abstract class as the calling class (e.g., AbstractBase.objects.do_something())
Thanks to mhsparks for the report.
