From 4480645ac3b4d3b72ee2880c774f849965d555d4 Mon Sep 17 00:00:00 2001
From: Malcolm Tredinnick <malcolm.tredinnick@gmail.com>
Date: Mon, 1 Sep 2008 00:49:03 +0000
Subject: [PATCH] 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                |  3 +++
 django/db/backends/mysql/base.py              |  1 +
 django/db/models/fields/related.py            |  9 ++++++--
 tests/regressiontests/model_regress/models.py | 23 +++++++++++++++++++
 4 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/django/db/backends/__init__.py b/django/db/backends/__init__.py
index be7aac4c03..23ce12960c 100644
--- a/django/db/backends/__init__.py
+++ b/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):
     """
diff --git a/django/db/backends/mysql/base.py b/django/db/backends/mysql/base.py
index b93453bc1e..9eb8dece83 100644
--- a/django/db/backends/mysql/base.py
+++ b/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):
diff --git a/django/db/models/fields/related.py b/django/db/models/fields/related.py
index 0513496be2..4532385a4f 100644
--- a/django/db/models/fields/related.py
+++ b/django/db/models/fields/related.py
@@ -684,7 +684,7 @@ class ForeignKey(RelatedField, Field):
 
     def contribute_to_related_class(self, cls, related):
         setattr(cls, related.get_accessor_name(), ForeignRelatedObjectsDescriptor(related))
-        
+
     def formfield(self, **kwargs):
         defaults = {'form_class': forms.ModelChoiceField, 'queryset': self.rel.to._default_manager.complex_filter(self.rel.limit_choices_to)}
         defaults.update(kwargs)
@@ -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()
 
diff --git a/tests/regressiontests/model_regress/models.py b/tests/regressiontests/model_regress/models.py
index d79bbca3be..2f2c2facd5 100644
--- a/tests/regressiontests/model_regress/models.py
+++ b/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>
+
 """
 }