Hi, AFAIK there is no such thing in the code or documentation. Nevertheless, for a paper I've published last year, I tried to create mathematical transcriptions at least for the I/O costs. http://dl.acm.org/citation.cfm?id=2236584.2236588&coll=DL&dl=ACM&CFID=309621631&CFTOKEN=77712718 Have a look at the appendix. Regards, Daniel Bausch Am 06.04.2013 12:51, schrieb dafNi: > Hello everybody! > > I'm trying to understand the the query planner's cost estimator. > I was not able to find anywhere the formulas that estimate the cost > of each operation that the optimizer produces. > > I only found this for the sequential scan: > SEQ SCAN = ( cpu_tuple_cost * rows ) + ( number of pages * seq_page_cost ) > where : > cpu_tuple_cost=0.01 > seq_page_cost=1.0 > and "rows" and "number of pages" are given in the query plan (via > EXPLAIN ANALYZE) > > I am wondering where could I find the rest formulas for the rest operations > (e.g. HashAggregate, Nested Loop, Hash Join, Index Scan, Sort, etc) > > I also looked at costsize.c but could not find a formula like the above > or maybe I > couldn't make sense of it > > > Thank you in advance! -- Daniel Bausch Wissenschaftlicher Mitarbeiter Technische Universität Darmstadt Fachbereich Informatik Fachgebiet Datenbanken und Verteilte Systeme Hochschulstraße 10 64289 Darmstadt Germany Tel.: +49 6151 16 6706 Fax: +49 6151 16 6229 -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
