[Xastir-Dev] Short list, stable release, then Xastir-2 development?
James Jefferson
jj at aprsworld.net
Thu Mar 13 18:49:07 EST 2003
On Thursday 13 March 2003 05:34 pm, Gerry Creager N5JXS wrote:
> If we were to take it a step further, PostGIS allows storage of spatial
> components. Polygons and their coordinate info (and metadata), anyone?
Gerry - I think the PostGIS is absolutely nescessary. I'm running into all
kinds of problems with MySQL and its lack of spatial indexing. I would wish a
similar fate on anybody.
An example: I have a table with about 10 million places around the world.
About 400 megabytes of data. It is indexed on latitude, longitude, and name.
Doing a query on name takes < 0.001 seconds. Doing a query on location (ie
show me points in a bounding box) takes ~ 6 seconds. MySQL chooses to use the
latitude index, then it has to retreive all of the matching rows from the
disk (lots of disk seeks involved here) and eliminate 99.99% of those rows
because they are outside of the longitude bounds.
I'd like to get PostGIS working enough to try a spatial index and see what
sort of performance gain I get. I'm guessing it will be dramatic.
(Is anybody with PostGIS experience willing to get it setup and running on one
of my aprsworld.net boxes? I've managed to install it, but it's
user/premissions are so screwy that I've never gotten to the point where I'm
actually allowed to put data in a PostGIS table ... that has rather stymied
my progress).
-Jim
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