From: pgsql-general-ow...@postgresql.org [mailto:pgsql-general-ow...@postgresql.org] On Behalf Of Felipe Santos Sent: Thursday, January 28, 2016 1:17 PM To: Joshua D. Drake <j...@commandprompt.com> Cc: Melvin Davidson <melvin6...@gmail.com>; David Rowley <david.row...@2ndquadrant.com>; pgsql-general@postgresql.org; Thomas Kellerer <spam_ea...@gmx.net> Subject: Re: [GENERAL] BRIN indexes
"Further to the point, it is self defeating to have more than one BRIN index on the table if the columns involved would have mutually non-adjacent pages." Not really, if both columns are ordered, BRIN will work "Therefore, it actually would be good to state that in the documentation, even it were just a comment." It is = "BRIN is designed for handling very large tables in which certain columns have some natural correlation with their physical location within the table" Link: http://www.postgresql.org/docs/devel/static/brin-intro.html Also, I did some tests and here are the results I got: Query with no index = completion time 43s Same Query with BRIN = completion time 14s / index size 0,5 MB Same Query without BRIN and with BTREE = completion time 10s / index size 5.000,00 MB As you can see, BRIN can save 99% of disk space for just a slightly worse performance. It seems like a huge improvement, given that your data fits BRIN's use case. Felipe, What kind of queries you used in your test? Where they based on clustering columns? Regards Igor Neyman
