Postgres ArrayField append

[Paul Grau]

I am using an ArrayField to store a list of dates. I would like to use update() to add a value to the list, only if the list doesn't contain it already.

The contains part is already supported by Django, but not the array_append.

​http://www.postgresql.org/docs/9.1/static/arrays.html#ARRAYS-MODIFYING

Eventually I'd like to be able to do something like this:

User.objects.exclude(active_in__contains=[current_month]).update(active_in=F('active_in') + [current_month])

which should result in this SQL:

UPDATE user_user SET active_in = array_append(active_in, [%s]) WHERE NOT(active_in @> ARRAY[%s]::varchar[]) ['2012-01']

PS: I want to use update instead of get() and save() for performance reasons.