Re: Planner issue

I'm guessing your data is actually more "clustered" than the
"correlation" stastic thinks it is.

Alex Turner wrote:
 >   trendmls=# explain analyze select listnum from propmain where
 >                      listprice<=300000 and listprice>=200000;


Is that a database of properties like land/houses?

If your table is clustered geographically (by zip code, etc),
the index scan might do quite well because all houses in a
neighborhood may have similar prices (and therefore live on
just a few disk pages).   However since high-priced neighborhoods
are scattered across the country, the optimizer would see
a very low "correlation" and not notice this clustering.


If this is the cause, one thing you could do is
CLUSTER your table on propmain_listprice_i.    I'm quite
confident it'll fix this particular query - but might
slow down other queries.