Django annotate count with a distinct field

Count can take a distinct argument, like so:

p = Project.objects.all().annotate(Count('informationunit__username', 
                                         distinct=True))

This doesn't seem to be documented, but you can find it in the source for Count.

If you just want to count the distinct values, you can use the distinct() and count() functions:

count = Project.objects.values('informationunit__username').distinct().count()

Project.objects.all().annotate(Count('informationunit__username', 
                                     distinct=True))

SQL SELECT field1, COUNT(DISTINCT(pk)) FROM project GROUP BY field1 ORDER BY NULL;

QuerySet

Project.objects.all().values(field1).annotate(count=Count('pk', distinct=True)).order_by()