This patch iproved two major parts in Django. First, the fields.related
was refactored. The main addition there was ForeignObject. Second, the
ORM now handles multicolumn joins in most cases, though there are still
cases that do not work correcly (split_exclude() for example).
In addition there were extesive changes to how GenericRelation works.
Before it was a fake m2m field, now it is a pure virtual fields and is
based on ForeignObject.
There is still much room for improvement. The related fields code is
still somewhat confusing, and how fields are represented in model._meta
should also be revisited.
This patch was written mostly by Jeremy Tillman with some final polish
by the committer.
Previously, depending on the database backend or the cursor type,
you'd need to double the percent signs in the query before passing
it to cursor.execute. Now cursor.execute consistently need percent
doubling whenever params argument is not None (placeholder substitution
will happen).
Thanks Thomas Güttler for the report and Walter Doekes for his work
on the patch.
This is provided as a new "validate_max" formset_factory option defaulting to
False, since the non-validating behavior of max_num is longstanding, and there
is certainly code relying on it. (In fact, even the Django admin relies on it
for the case where there are more existing inlines than the given max_num). It
may be that at some point we want to deprecate validate_max=False and
eventually remove the option, but this commit takes no steps in that direction.
This also fixes the DoS-prevention absolute_max enforcement so that it causes a
form validation error rather than an IndexError, and ensures that absolute_max
is always 1000 more than max_num, to prevent surprising changes in behavior
with max_num close to absolute_max.
Lastly, this commit fixes the previous inconsistency between a regular formset
and a model formset in the precedence of max_num and initial data. Previously
in a regular formset, if the provided initial data was longer than max_num, it
was truncated; in a model formset, all initial forms would be displayed
regardless of max_num. Now regular formsets are the same as model formsets; all
initial forms are displayed, even if more than max_num. (But if validate_max is
True, submitting these forms will result in a "too many forms" validation
error!) This combination of behaviors was chosen to keep the max_num validation
simple and consistent, and avoid silent data loss due to truncation of initial
data.
Thanks to Preston for discussion of the design choices.
The ticket dealt with a case where one query had .exclude() that
produced a subquery, the other query had a join to the same model that
was subqueried in the first query. This was already fixed in master, so
only test added.
