The following bug has been logged on the website: Bug reference: 8130 Logged by: Stefan de Konink Email address: ste...@konink.de PostgreSQL version: 9.2.4 Operating system: Linux Description:
We figured out that two very close query give a massive difference performance between using select * vs select id. SELECT * FROM ambit_privateevent_calendars AS a ,ambit_privateevent AS b ,ambit_calendarsubscription AS c ,ambit_calendar AS d WHERE c.calendar_id = d.id AND a.privateevent_id = b.id AND c.user_id = 1270 AND c.calendar_id = a.calendar_id AND c.STATUS IN ( 1 ,8 ,2 ,15 ,18 ,4 ,12 ,20 ) AND NOT b.main_recurrence = true; With some help on IRC we figured out that "there was a bugfix in hash estimation recently and I was hoping you were older than that", but since we are not: PostgreSQL 9.2.4 on x86_64-pc-linux-gnu, compiled by x86_64-pc-linux-gnu-gcc (Gentoo 4.7.2-r1 p1.6, pie-0.5.5) 4.7.2, 64-bit ...there might still be a bug around. We compare: http://explain.depesz.com/s/jRx http://explain.depesz.com/s/eKE By setting "set enable_hashjoin = off;" performance in our entire application increased 30 fold in throughput, which was a bit unexpected but highly appreciated. The result of the last query: http://explain.depesz.com/s/AWB What can we do to provide a bit more of information? -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs