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 22022,Allow field subclasses to require additional SQL,Marc Tamlyn,nobody,"'''Problem''' In postgres, a number of data types require a specific extension to be installed. We have one instance of this in core at present, which is the `postgis` extension. Our documentation recommends[1] (in postgres 9.1+) that you explicitly create the extension in your primary database by hand, and then we customise the `_create_test_db` method on the postgis database backend to ensure the test database has the relevant extensions installed. Other third party apps[2] recommend adding the extension to the template to ensure it's present in tests. I wish to avoid adding a custom backend to d.c.postgres if at all possible, especially as using it in conjunction with gis should be permissible. Consequently, I'd like if possible for model fields to have `pre_create_sql` to allow each individual field to create the extensions as needed. The same mechanism could also be used for a user defined custom field to create functions which could then be used as a custom transform object. This feature will be useful for: 1) one part of the de-hack-gis project 2) hstore 3) citext, trigrams, generating uuids database side and other possible future features of d.c.postgres I've written a draft patch[3]. It probably needs some work (hence patch needs improvement) but an initial review of the names and code layout would be useful. [1] https://docs.djangoproject.com/en/1.6/ref/contrib/gis/install/postgis/#creating-a-spatial-database-with-postgis-2-0-and-postgresql-9-1 [2] http://djangonauts.github.io/django-hstore/#_running_tests [3] https://github.com/django/django/pull/2266",New feature,closed,"Database layer (models, ORM)",dev,Normal,wontfix,,,Accepted,1,0,0,1,0,0