Re: Planner problems in 8.2.4 and 8.2.5

Gregory Stark <stark(at)enterprisedb(dot)com> writes:
> "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
>> It's been clear for quite awhile that a stats target of 10 is often
>> too low, but no one has done the legwork to establish what a more
>> reasonable tradeoff point would be.

> Any ideas on what measurements would be interesting for this?

Time to run ANALYZE on large tables, extra planning time for queries of
various complexities; versus whether you actually get a better plan or
not.

In a quick look at selfuncs.c, it appears that the worst planner hit
would be for eqjoin selectivities between non-unique columns (ie, those
having MCV lists). The number of operations is O(N^2) if there are
N values in each MCV list.

regards, tom lane