On Thu, Nov 5, 2015 at 1:11 AM, Artem Tomyuk <ad...@leboutique.com> wrote: > Hi all. > > Is the speed of hash operations stands on the performance of CPU?
Yes, but the variation is probably not as much as the raw timing in your example indicates. > Below you can see part from output of explain analyze command > > Intel(R) Xeon(R) CPU E7520 @ 1.87GHz > > " -> Hash (cost=337389.43..337389.43 rows=3224443 width=34) > (actual time=15046.382..15046.382 rows=3225191 loops=1)" > " Buckets: 524288 Batches: 1 Memory Usage: 207874kB" A lot of that time was probably spent reading the data off of disk so that it could hash it. You should turn track_io_timing on, run "explain (analyze, buffers) ..." and then show the entire explain output, or at least also show the entries downstream of the Hash node. Cheers, Jeff -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
