On Tue, Jan 31, 2017 at 5:53 PM, Rahila Syed <rahilasye...@gmail.com> wrote: > Hello, > >>Agreed, that it makes sense to consider only the number of pages to >>scan for computation of parallel workers. I think for index scan we >>should consider both index and heap pages that need to be scanned >>(costing of index scan consider both index and heap pages). I thin >>where considering heap pages matter more is when the finally selected >>rows are scattered across heap pages or we need to apply a filter on >>rows after fetching from the heap. OTOH, we can consider just pages >>in the index as that is where mainly the parallelism works > IMO, considering just index pages will give a better estimate of work to be > done > in parallel. As the amount of work/number of pages divided amongst workers > is irrespective of > the number of heap pages scanned. >
Yeah, I understand that point and I can see there is strong argument to do that way, but let's wait and see what others including Robert have to say about this point. -- With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
