Fixed #8316 -- Put tighter restrictions on the type of Foreign Key fields

created for MySQL (because MySQL + InnoDB has those restrictions).
Patch from julianb.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8782 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/backends/__init__.py

@@ -71,6 +71,9 @@ class BaseDatabaseFeatures(object):
     interprets_empty_strings_as_nulls = False
     can_use_chunked_reads = True
     uses_savepoints = False
+    # If True, don't use integer foreign keys referring to, e.g., positive
+    # integer primary keys.
+    related_fields_match_type = False
 
 class BaseDatabaseOperations(object):
     """

django/db/backends/mysql/base.py

@@ -110,6 +110,7 @@ class CursorWrapper(object):
 class DatabaseFeatures(BaseDatabaseFeatures):
     empty_fetchmany_value = ()
     update_can_self_select = False
+    related_fields_match_type = True
 
 class DatabaseOperations(BaseDatabaseOperations):
     def date_extract_sql(self, lookup_type, field_name):

django/db/models/fields/related.py

@@ -695,8 +695,13 @@ class ForeignKey(RelatedField, Field):
         # of the field to which it points. An exception is if the ForeignKey
         # points to an AutoField/PositiveIntegerField/PositiveSmallIntegerField,
         # in which case the column type is simply that of an IntegerField.
+        # If the database needs similar types for key fields however, the only
+        # thing we can do is making AutoField an IntegerField.
         rel_field = self.rel.get_related_field()
-        if isinstance(rel_field, (AutoField, PositiveIntegerField, PositiveSmallIntegerField)):
+        if (isinstance(rel_field, AutoField) or
+                (not connection.features.related_fields_match_type and
+                isinstance(rel_field, (PositiveIntegerField,
+                                       PositiveSmallIntegerField)))):
             return IntegerField().db_type()
         return rel_field.db_type()
 

tests/regressiontests/model_regress/models.py

@@ -32,6 +32,20 @@ class Party(models.Model):
 class Event(models.Model):
     when = models.DateTimeField()
 
+class Department(models.Model):
+    id = models.PositiveIntegerField(primary_key=True)
+    name = models.CharField(max_length=200)
+
+    def __unicode__(self):
+        return self.name
+
+class Worker(models.Model):
+    department = models.ForeignKey(Department)
+    name = models.CharField(max_length=200)
+
+    def __unicode__(self):
+        return self.name
+
 __test__ = {'API_TESTS': """
 (NOTE: Part of the regression test here is merely parsing the model
 declaration. The verbose_name, in particular, did not always work.)
@@ -95,5 +109,14 @@ u''
 datetime.datetime(2000, 1, 1, 13, 1, 1)
 >>> e.get_previous_by_when().when
 datetime.datetime(2000, 1, 1, 6, 1, 1)
+
+# Check Department and Worker
+>>> d = Department(id=10, name='IT')
+>>> d.save()
+>>> w = Worker(department=d, name='Full-time')
+>>> w.save()
+>>> w
+<Worker: Full-time>
+
 """
 }