On Thu, Jan 22, 2015 at 5:57 AM, Amit Kapila <amit.kapil...@gmail.com> wrote: > 1. Scanning block-by-block has negative impact on performance and > I thin it will degrade more if we increase parallel count as that can lead > to more randomness. > > 2. Scanning in fixed chunks improves the performance. Increasing > parallel count to a very large number might impact the performance, > but I think we can have a lower bound below which we will not allow > multiple processes to scan the relation.
I'm confused. Your actual test numbers seem to show that the performance with the block-by-block approach was slightly higher with parallelism than without, where as the performance with the chunk-by-chunk approach was lower with parallelism than without, but the text quoted above, summarizing those numbers, says the opposite. Also, I think testing with 2 workers is probably not enough. I think we should test with 8 or even 16. -- 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
