#3615: Can't define forward references in fixtures using MySQL with InnoDB
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Reporter: russellm | Owner: nobody
Status: new | Milestone:
Component: Database layer (models, ORM) | Version: SVN
Resolution: | Keywords: mysql
innodb myisam reference fixture
Stage: Accepted | Has_patch: 0
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Comment (by ramiro):
Replying to [comment:9 kmtracey]:
> As it is it isn't clear to me if this approach really helps at all for
MS SQL Server, since it apparently wants table names on which to turn off
constraint checking, but maybe someone who knows more (Ramiro?) on that
topic can comment...)
You are right, implementing this in SQL server doesn't imply controlling
things by toggling a global variable but by ALTERing TABLE so the names
of the tables are needed.
So far, I've solved this by cloning the `loaddata` management command and
modifying the copy to insert calls to the two new methods in the same way
it's done in the patches we have posted. But they mostly only serve to
mark the boundaries of a period of time in which insertions of forward
references are possible. Real work is done in a hook that is a no-op
except when running during one of such periods, it's called every time
fixtures for a model are going to be loaded, in these edges the model is
introspected in search of outgoing FKs and M2M, if there are any the
corresponding ALTER TABLEs are performed.
http://code.google.com/p/django-
pyodbc/source/browse/trunk/sql_server/extra/management/commands/ss_loaddata.py#165
(Currently all the constraint checks for a given table are deactivated,
but it can be made more fine grained and to have the less overall impact
possible in the DB by even introspecting the names of the constraints and
only deactivating these. This is in my TODO list)
So, I think a backend for SQL Server could make use of the
begin_defer_constraint_checks()/end_defer_constraint_checks() methods but
when it comes to table names, being able to do thing in a way as granular
as possible (by no touching tables that aren't involved) would need an
additional hook (similar to the one I created) being provided in some way.
--
Ticket URL: <http://code.djangoproject.com/ticket/3615#comment:11>
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