Security issue

Hi pg-admin gurus,
I think my question is easy, so: How can I disable table creation on a database
for a user different the creator? I have read in the Administrator's Guide it's
disabled by default, but I have made some tests, and ANY user could create
tables. What do I have to make? I'm using PostgreSQL 6.5.2 on a Sun Ultra-60
with Solaris 2.7, and I compiled PostgreSQL myself.

Thanks in advance,
José María
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José María Fernández González e-mail: jmfernandez(at)cnb(dot)uam(dot)es
Tlfn: (+34) 91 585 46 69 Fax: (+34) 91 585 45 06
Grupo de Diseño de Proteinas Protein Design Group
Centro Nacional de Biotecnología National Center of Biotechnology
C.P.: 28049 Zip Code: 28049
Campus Universidad Autónoma. Cantoblanco, Madrid, Spain.