On Wed, Dec 16, 2015 at 1:34 AM, Amit Kapila <amit.kapil...@gmail.com> wrote: > Yes, thats one thing I wanted to know, yet another point which is not > clear to me about this Async infrastructure is why the current > infrastructure > of Parallelism can't be used to achieve the Async benefits of ForeignScan?
Well, all a ForeignScan by postgres_fdw does is read the tuples that are generated remotely. Turning around and sticking those into a Funnel doesn't seem like it gains much: now instead of having to read tuples from someplace, the leader has to read tuples from some other place. Yeah, there are cases where it could win, like when there's a selective nonpushable qual, but that's not that exciting. There's another, more serious problem: if the leader has a connection open to the remote server and that connection is in mid-transaction, you can't have a worker open a new connection without changing the semantics. Working around that problem looks hard to me. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
