The tool to tweak the query planner parameters mentioned in the article sounds very useful. Can we download it somewhere, either as binary or source code ?
Sébastien On Mon, Apr 8, 2013 at 2:44 AM, Daniel Bausch <bau...@dvs.tu-darmstadt.de>wrote: > 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@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general >
