[postgis-users] Trying to figure out how statistics for the plannerwork

strk at refractions.net strk at refractions.net
Sat Mar 11 10:46:00 PST 2006

Happy to hear making it a define helped :)
Note that there should also be a define for fine-tuning
standard deviation computing. The standard deviation
computation has been introduced to avoid problems when
hard deviant are present (possibly bogus entries completely
outside of the *real*  spatial domain, like geoms with
wrong projection and similar).

I wonder if it would be worth an additional final check
to abort the standard-deviation computed bbox when
the number of "hard-deviant" is above a given threshold...


On Fri, Mar 10, 2006 at 10:49:15AM -0800, Steve Wormley wrote:
> Thanks for the responses on this issue.
> I finally broke down and enabled DEBUG_GEOMETRY_STATS in lwgeom_estimate.c
> and realized that the standard deviation computation was optimizing out this
> section of data from the created histogram.
> Since my data isn't normally distributed enough for USE_STANDARD_DEVIATION
> to be useful, I disabled it and ended up with much better estimates for the
> areas like this with only a few thousand points.
> Thanks,
> -Steve Wormley
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