Q:

How to prevent a user from being able to see other databases and the tables from other databases?

I want to create a postgres user that can access only one database on the postgres server at all.
Currently my flow is:
create database database1;
create user user1 with password 'pass';
grant all privileges on database database1 to user1;

but user1 can still see a list of dbs, users, tables etc. Is there a way to prevent that user from seeing that info? The user needs to be able to write to and read from that db.
Thanks a lot.

A:

Each user can see other databases and roles listed, but should not be able to see tables in other databases, ever.
If you revoke CONNECT privilege on all databases except the allotted one, the user will not be able to access the contents of other databases.
Roles and database names are global, and not readily blockable.  You can try Frank Heikens suggestion of selective revocations on the system tables, but you take risks to do that.  PostgreSQL developers on the usenet mailing lists have discouraged tampering with access to the system catalogs.  
Psql, among other tools, assumes they will be available and functions poorly without them.
Why is knowing the names of other databases and roles so bad?

