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 ?
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.
> 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
