[1.5.x] Fixed #20168 - Generalized a PostgreSQL specific database query in the docs.
[1.5.x] Fixed #20168 - Generalized a PostgreSQL specific database query in the docs.

Thanks Russ for the suggestion.

Backport of c119d0f152 from master

bliti/django-nonrel-1.5,alx-eu/django,imtapps/django-imt-fork,alx-eu/django,imtapps/django-imt-fork,ccn-2m/django,hasadna/django,bliti/django-nonrel-1.5,alx-eu/django,ccn-2m/django,imtapps/django-imt-fork,bliti/django-nonrel-1.5,ccn-2m/django,hasadna/django,hasadna/django,alx-eu/django,ccn-2m/django