Re: Radius of a zip code

On Fri, Dec 26, 2003 at 10:34:04PM -0600, Bruno Wolff III wrote:
> On Fri, Dec 26, 2003 at 19:42:44 -0700,
>   Michael Fuhr <mike@fuhr.org> wrote:
> > 
> > I have several databases with lat/lon coordinates and frequently make
> > "show me all records within a certain distance of this point" queries.
> > I wrote a haversine() function that uses the Haversine Formula to
> > calculate the great circle distance between two points on a sphere
> > (assuming the earth is a perfect sphere is accurate enough for my uses).
> > Here's a web site with related info:
> 
> The distance operator in contrib/earthdistance got changed to use
> haversine instead of the naive formula in 7.3. In 7.4 it also provides
> some functions that work with contrib/cube that allow for indexed
> searches.

I'll have to take a closer look at contrib/earthdistance.  I'm using the
function I wrote for legacy reasons -- I had ported an application from
another DBMS to PostgreSQL and wanted to make as few changes as possible,
so I ported the haversine() function that I had already written.

Incidentally, I see the following in README.earthdistance:
 A note on testing C extensions - it seems not enough to drop a function and re-create it - if I change a function, I
haveto stop and restart the backend for the new version to be seen. I guess it would be too messy to track which
functionsare added from a .so and do a dlclose when the last one is dropped.
 

Maybe you've already figured it out, but LOAD should allow you to reload
a .so file without having to restart the backend.

http://www.postgresql.org/docs/current/static/sql-load.html

-- 
Michael Fuhr
http://www.fuhr.org/~mfuhr/