"Paul Ramsey" <[EMAIL PROTECTED]> writes: > The "optimized" form gets cached and retrieved from a memory context. > Each time the function is run within a statement it checks the cache, > and sees if one of its arguments are the same as the last time around. > If so, it uses the prepared version of that argument. If not, it > builds a new prepared version and caches that.
> The key here is being able to check the identify of the arguments... > is this argument A the same as the one we processed last time? One way > is to do a memcmp. But it seems likely that PgSQL knows exactly > whether it is running a nested loop, or a literal, and could tell > somehow that argument A is the same with each call. Not really. Certainly there's no way that that information would propagate into function calls. In the special case where your argument is a literal constant, I think there is enough information available to detect that that's the case (look at get_fn_expr_argtype). But if it's not, there's no very good way to know whether it's the same as last time. Perhaps it would be worth changing your on-disk storage format to allow cheaper checking? For instance include a hash value. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers