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Fixed #22445 -- Added how to perform a reverse data migration to topic guide. 

Thanks Karen Tracey for the report.
This commit is contained in:
Tim Graham 2014-04-27 15:19:54 -04:00
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commit 1ce759b69f
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docs/topics/migrations.txt
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@ -389,6 +389,11 @@ need to do is use the historical model and iterate over the rows::
Once that's done, we can just run ``python manage.py migrate`` as normal and Once that's done, we can just run ``python manage.py migrate`` as normal and
the data migration will run in place alongside other migrations. the data migration will run in place alongside other migrations.
You can pass a second callable to
:class:`~django.db.migrations.operations.RunPython` to run whatever logic you
want executed when migrating backwards. If this callable is omitted, migrating
backwards will raise an exception.
If you're interested in the more advanced migration operations, or want If you're interested in the more advanced migration operations, or want
to be able to write your own, see the :doc:`migration operations reference to be able to write your own, see the :doc:`migration operations reference
</ref/migration-operations>`. </ref/migration-operations>`.