Re: optimizer's cost formulas

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 <bausch(at)dvs(dot)tu-darmstadt(dot)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
>
>
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