database quota

Is there a way to set up a disk size (data size maybe) on postgresql
databases (files)?
How to recognize which directory is connected to a certain database
(ie. is 16345 a bip_um database?).

Browsed through google, came up with almost nothing. I've read
that setting group/user quotas on files doesn't work, since
postgresql daemon sets postgres as a owner to newly created files.

Regards,
-- 
   Marcin Gil
   marcin.gil @ audax.com.pl, tel. 694972082
   OIS Audax Sp. z o.o., ul. Barlickiego 4, 97-200 Tomaszów Mazowiecki
   tel/fax (44) 7247530, 7244401