Fixed #7314 -- Changed the way extra() bits are handled when QuerySets are merged.

Also added a section to the documentation to indicate why it's probably not a
good idea to rely on this feature for complex stuff. Garbage in, garbage out
applies even to Django code.

Thanks to erik for the test case for this one.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7791 bcc190cf-cafb-0310-a4f2-bffc1f526a37

2 files changed, 55 insertions, 0 deletions

diff --git a/tests/regressiontests/extra_regress/__init__.py b/tests/regressiontests/extra_regress/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/regressiontests/extra_regress/__init__.py
diff --git a/tests/regressiontests/extra_regress/models.py b/tests/regressiontests/extra_regress/models.py
new file mode 100644
index 0000000000..3bcc3075ec
--- /dev/null
+++ b/tests/regressiontests/extra_regress/models.py
@@ -0,0 +1,55 @@
+import copy
+
+from django.db import models
+from django.db.models.query import Q
+
+
+class RevisionableModel(models.Model):
+    base = models.ForeignKey('self', null=True)
+    title = models.CharField(blank=True, max_length=255)
+
+    def __unicode__(self):
+        return u"%s (%s, %s)" % (self.title, self.id, self.base.id)
+
+    def save(self):
+        super(RevisionableModel, self).save()
+        if not self.base:
+            self.base = self
+            super(RevisionableModel, self).save()
+
+    def new_revision(self):
+        new_revision = copy.copy(self)
+        new_revision.pk = None
+        return new_revision
+
+__test__ = {"API_TESTS": """
+### Regression tests for #7314 and #7372
+
+>>> rm = RevisionableModel.objects.create(title='First Revision')
+>>> rm.pk, rm.base.pk
+(1, 1)
+
+>>> rm2 = rm.new_revision()
+>>> rm2.title = "Second Revision"
+>>> rm2.save()
+>>> print u"%s of %s" % (rm2.title, rm2.base.title)
+Second Revision of First Revision
+
+>>> rm2.pk, rm2.base.pk
+(2, 1)
+
+Queryset to match most recent revision:
+>>> qs = RevisionableModel.objects.extra(where=["%(table)s.id IN (SELECT MAX(rev.id) FROM %(table)s AS rev GROUP BY rev.base_id)" % {'table': RevisionableModel._meta.db_table,}],)
+>>> qs
+[<RevisionableModel: Second Revision (2, 1)>]
+
+Queryset to search for string in title:
+>>> qs2 = RevisionableModel.objects.filter(title__contains="Revision")
+>>> qs2
+[<RevisionableModel: First Revision (1, 1)>, <RevisionableModel: Second Revision (2, 1)>]
+
+Following queryset should return the most recent revision:
+>>> qs & qs2
+[<RevisionableModel: Second Revision (2, 1)>]
+
+"""}