On Fri, Mar 13, 2015 at 8:59 AM, Amit Kapila <amit.kapil...@gmail.com> wrote: > We can't directly call DestroyParallelContext() to terminate workers as > it can so happen that by that time some of the workers are still not > started.
That shouldn't be a problem. TerminateBackgroundWorker() not only kills an existing worker if there is one, but also tells the postmaster that if it hasn't started the worker yet, it should not bother. So at the conclusion of the first loop inside DestroyParallelContext(), every running worker will have received SIGTERM and no more workers will be started. > So that can lead to problem. I think what we need here is a way to know > whether all workers are started. (basically need a new function >WaitForParallelWorkersToStart()). This API needs to be provided by > parallel-mode patch. I don't think so. DestroyParallelContext() is intended to be good enough for this purpose; if it's not, we should fix that instead of adding a new function. No matter what, re-scanning a parallel node is not going to be very efficient. But the way to deal with that is to make sure that such nodes have a substantial startup cost, so that the planner won't pick them in the case where it isn't going to work out well. -- 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
