I'm interested in the response time instead of the quality of it, that is, if this response is (or not) a best plan. Thus, my interest on the response time is to compare the GEQO algorithm with other solutions for optimization of queries, more specificaly when there are 12 or more tables evolved. Accordingly, the algorithm of dynamic programming becomes hard because of the computational cost to obtain the optimal plan.
My question is to know what tool or method was used to test the GEQO algorithm or if there is some documentation that explain how the geqo was tested.
Regards,
Tarcizio Bini
2008/5/28 Simon Riggs <
simon@2ndquadrant.com>:
On Wed, 2008-05-28 at 13:13 -0300, Tarcizio Bini wrote:
> Of course, the geqo_threshold can be changed so that the geqo be
> performed in queries that have less than 12 tables. However, we aim to
> test the GEQO algorithm in conditions where the standard algorithm
> (dynamic programming) has a high cost to calculate the query plan.
My understanding is the GEQO cannot arrive at a better plan than the
standard optimizer, so unless you wish to measure planning time there
isn't much to test. What is the quality of the plans it generates? Well
that varies according to the input; sometimes it gets the right plan,
other times it doesn't get close.
--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Training, Services and Support
