[Zope] ZSQL with different user

[Pier Luigi Fiorini]

Hello,
I'm developing a Zope application that uses a PostgreSQL connection and 
several ZSQL objects.
People should log in using a Postgres user and ZSQL object should be executed 
by the user that's logged in. Multiple people can be logged at the same time.
Unfortunately it is not possible because the same Postgres connection is used 
by all the ZSQL object. Is there a way to change the user executing a ZSQL 
query?

An alternative would be to log into the event.log some information (like the 
username, that's stored in the session) and the query source.

Can you point me to some information?

Thanks