I don't fully understand the performance implications here.

Say I was using this for a blog engine, and I wanted to run this SQL query:

    select * from entries;

But I actually only want to get back entries that my current user is allowed to view - where author_id = 57 for example.

Would PostgreSQL automatically turn the above query into the equivalent of this:

    select * from entries where author_id = 57;

And hence run quickly (assuming there's an index on that author_id column)?

Or would it need to run an additional SQL query check for every single row returned by my query to check row permissions, adding up to a lot of extra overhead?