id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
13663	Foreign Key to table in another database fails	berto	nobody	"I'm working with a legacy database that references records in another database by ID.  I would like to use Django's `ForeignKey` field to access this data.  Out of the box, this fails with the error below.  When using `ForeignKey`, the query is bound to using the same db as the current model.  I'm not sure if it's the right thing to do, but the problem is solved by removing `using()` from the query in [http://code.djangoproject.com/browser/django/trunk/django/db/models/fields/related.py?rev=13037#L302 django/db/models/fields/related.py] on line 302.

I think being able to use Django's `ForeignKey` and friends across databases would be quite useful, albeit not being able to set database-level contraints on the relations.

Thanks.

{{{
---------------------------------------------------------------------------
DatabaseError                             Traceback (most recent call last)

/Users/berto/repo/webapp/<ipython console> in <module>()

/Users/berto/local/opt/django/current/django/db/models/fields/related.py in __get__(self, instance, instance_type)
    300                 rel_obj = rel_mgr.using(db).get(**params)
    301             else:
--> 302                 rel_obj = QuerySet(self.field.rel.to).using(db).get(**params)
    303             setattr(instance, cache_name, rel_obj)
    304             return rel_obj

/Users/berto/local/opt/django/current/django/db/models/query.pyc in get(self, *args, **kwargs)
    334         if self.query.can_filter():
    335             clone = clone.order_by()
--> 336         num = len(clone)
    337         if num == 1:
    338             return clone._result_cache[0]

/Users/berto/local/opt/django/current/django/db/models/query.pyc in __len__(self)
     79                 self._result_cache = list(self._iter)
     80             else:
---> 81                 self._result_cache = list(self.iterator())
     82         elif self._iter:
     83             self._result_cache.extend(list(self._iter))

/Users/berto/local/opt/django/current/django/db/models/query.pyc in iterator(self)
    267 
    268         compiler = self.query.get_compiler(using=self.db)
--> 269         for row in compiler.results_iter():
    270             if fill_cache:
    271                 obj, _ = get_cached_row(self.model, row,

/Users/berto/local/opt/django/current/django/db/models/sql/compiler.pyc in results_iter(self)
    670         resolve_columns = hasattr(self, 'resolve_columns')
    671         fields = None
--> 672         for rows in self.execute_sql(MULTI):
    673             for row in rows:
    674                 if resolve_columns:

/Users/berto/local/opt/django/current/django/db/models/sql/compiler.pyc in execute_sql(self, result_type)
    725 
    726         cursor = self.connection.cursor()
--> 727         cursor.execute(sql, params)
    728 
    729         if not result_type:

/Users/berto/local/opt/django/current/django/db/backends/util.pyc in execute(self, sql, params)
     13         start = time()
     14         try:
---> 15             return self.cursor.execute(sql, params)
     16         finally:
     17             stop = time()

/Users/berto/local/opt/django/current/django/db/backends/postgresql_psycopg2/base.pyc in execute(self, query, args)
     42     def execute(self, query, args=None):
     43         try:
---> 44             return self.cursor.execute(query, args)
     45         except Database.IntegrityError, e:
     46             raise utils.IntegrityError, utils.IntegrityError(*tuple(e)), sys.exc_info()[2]

DatabaseError: current transaction is aborted, commands ignored until end of transaction block
}}}

"	New feature	closed	Database layer (models, ORM)	1.2	Normal	wontfix			Someday/Maybe	0	0	0	0	0	0