> > On 10/23/10 11:01 AM, Craig Ringer wrote: > > Yep. As for not explicitly mentioning "lower" roles when granting a > > higher role (ie "admin" isn't also a "user") - role inheritance. > > I knew about role inheritance, I just didn't know about the > pg_has_role() function for determining if a user has a role. That's > helpful, but I really don't want to be hitting the database with a > pg_has_role() call for every time I want to check if a user should have > access to a certain page or function in my application. > > Why not? Performance? It's just one function call.
It's potentially a fair bit more than that. It requires a new connection (tcp connection, backend startup, auth, etc) or borrowing one from a pool. If the pool is server side there's still a tcp connection with the associated latency. Then there's a round trip for the query and result. Processing the result. etc. It's not trivial, especially if your client and server aren't co-located.
This applies to any arbitrary SQL command. I don't see the problem here. Caching the privileges on the client side - is a good idea, but there is a perennial problem that I see very clearly - cache invalidation.
Like you, I'd suggest using information_schema for the job.
