Re: Re: what worked: performance improvements for geo-spatial searching on FreeBSD

[Oleg Bartunov <oleg(at)sai(dot)msu(dot)su>]

On Tue, 8 Apr 2008, Mark Stosberg wrote:

> Oleg Bartunov wrote:
> > Mark,
> >
> > do you know about our sky segmentation code Q3C,
> > see details http://www.sai.msu.su/~megera/wiki/SkyPixelization
> > We use it for billions objects in database and quite happy.
>
> Oleg,
>
> Thanks for the response. That sounds interesting, but it's not clear to me 
> how I would put together a geo-spatial search calculating distances around 
> the curvature of the earth using this technique. Is there is a SQL sample for 
> this that you could point to?

it's not about calculating distances, but about searching objects around
given point.

> Also, I didn't recognize the names of the techniques you were benchmarking 
> against "RADEC" and "Rtree", are either of these related to the 
> "earthdistance" or "cube()" based searches I would have used already?

Rtree is a standard spatial tree, RADEC - is naive approach of 
having two indexes, one on ra (right ascension) and another - on dec (declination).
Both are an astronomical coordinates.

>  Mark

	Regards,
		Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83