On Jan 4, 2010, at 1:59 PM, Robert Haas wrote: > The thing is, PostgreSQL doesn't know at planning time what the value of > current_user() will be, so the plan can't depend on that; the planner > just takes its best shot.
current_user() is a stable function and the manual is explicit that the result of stable function can be used in an index scan: "A STABLE function cannot modify the database and is guaranteed to return the same results given the same arguments for all rows within a single statement. This category allows the optimizer to optimize multiple calls of the function to a single call. In particular, it is safe to use an expression containing such a function in an index scan condition. (Since an index scan will evaluate the comparison value only once, not once at each row, it is not valid to use a VOLATILE function in an index scan condition.)" postgres=# select provolatile from pg_proc where proname = 'current_user'; provolatile ------------- s So, I think the OP's question is still valid. Erik Jones, Database Administrator Engine Yard Support, Scalability, Reliability 866.518.9273 x 260 Location: US/Pacific IRC: mage2k -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
