Re: updated SORT/LIMIT patch

Gregory Stark <stark@enterprisedb.com> writes:
> It doesn't look like the timing of the ExecRescan is an issue at all. There
> are plenty of nodes that Rescan their children much later than when they first
> start up. Even Nested Loop does so.

Right, but separating the child rescan from the tuplestore rescan bugs me.
Another problem is that the proposed patch does a child rescan call that
might (usually would) be unnecessary.

I am thinking that a cleaner fix is probably to make ExecRescanLimit do
the recompute_limits() bit immediately, so that the new limits are
available to the Sort node when it gets the rescan call.  The comment
about timing of recompute_limits() is referring to the fact that
parameters aren't set at ExecInitLimit() time, but I believe they are
(and should be) available at Rescan time.  Will give it a try anyway.

            regards, tom lane