Use of deferred fields in index_queryset breaks search

In my index's index_queryset method I use MyModel.objects.only() to limit the amount of data Haystack has to pull from the database. This works, but then the models are stored in Solr with a "django_ct" field with a mangled name such as "music.track_deferred_album_purchase_only_can_purchase_13e21ebf5814beb5662fa2c54730ecc1".

Later, when I go do a search with SearchQuerySet(), Haystack filters on "django_ct=music.track". Since all the models were stored with a different "django_ct" field, the search returns no results. The problem is that Haystack uses obj._meta.module_name to figure out the value of "django_ct", but for some reason, when using only() in QuerySets, django stores a different name for module_name.

Start at the index_queryset path and the code that generates the django_ct value, then trace how QuerySet.only() changes _meta.module_name. Reproduce the deferred-field case and compare indexing with SearchQuerySet filtering. Done means deferred querysets retain the normal content-type value and indexed records remain searchable.