On 2017/03/14 10:08, Corey Huinker wrote: >> I don't think the plan itself will change as a result of applying this >> patch. You might however be able to observe some performance improvement. > > I could see no performance improvement, even with 16 separate queries > combined with UNION ALL. Query performance was always with +/- 10% of a 9.6 > instance given the same script. I must be missing something.
Hmm, maybe I'm missing something too. Anyway, here is an older message on this thread from Horiguchi-san where he shared some of the test cases that this patch improves performance for: https://www.postgresql.org/message-id/20161018.103051.30820907.horiguchi.kyotaro%40lab.ntt.co.jp >From that message: <quote> I measured performance and had the following result. t0 - SELECT sum(a) FROM <local single table>; pl - SELECT sum(a) FROM <4 local children>; pf0 - SELECT sum(a) FROM <4 foreign children on single connection>; pf1 - SELECT sum(a) FROM <4 foreign children on dedicate connections>; The result is written as "time<ms> (std dev <ms>)" sync t0: 3820.33 ( 1.88) pl: 1608.59 ( 12.06) pf0: 7928.29 ( 46.58) pf1: 8023.16 ( 26.43) async t0: 3806.31 ( 4.49) 0.4% faster (should be error) pl: 1629.17 ( 0.29) 1.3% slower pf0: 6447.07 ( 25.19) 18.7% faster pf1: 1876.80 ( 47.13) 76.6% faster </quote> IIUC, pf0 and pf1 is the same test case (all 4 foreign tables target the same server) measured with different implementations of the patch. Thanks, Amit -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
