Re: detecting poor query plans

>>>>> "Neil" == Neil Conway <neilc@samurai.com> writes:
   Neil> It occurred to me that these kinds of poor planning   Neil> decisions could easily be detected by PostgreSQL
itself:  Neil> after we've finished executing a plan, we can trivially   Neil> compare the # of results produced by
eachnode in the query   Neil> tree with the # of results the planner expected that node to   Neil> produce (look at
EXPLAINANALYZE, for example). If the
 

Indeed. This is the approach being followed by the LeO project
(Learning Optimizer) at IBM Almaden. 

http://www.almaden.ibm.com/software/dm/SMART/leo.shtml

There is a vldb paper that describes it .. 

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Sailesh
http://www.cs.berkeley.edu/~sailesh