[postgis] Native PostGIS support in mapserver

[Dave Blasby]

PostGIS now has two connection to mapserver
(http://mapserver.gis.umn.edu) - one is through Frank Warmerdam's OGR,
and the other is native support.

I just sent this message to the mapserver mailing list.

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"Stephen Lime" wrote:

> Also note that the PostGIS authors are working on native support. They've been
> shown around the source and have started working on it, no word on progress
> though. Also note that a couple of groups are working on Oracle Spatial support...

Native PostGIS support in mapserver is in the testing phase.  We have
been testing it on (1) solaris PostGIS server with an i386 linux
mapserver client and (2) PostGIS and mapserver on the same i386 server.  

The PostGIS performance has been about 1/2 to 1/3 the speed as using
shapefiles on a RAID device.

Our test machine is a fast athlon running linux with a RAID filesystem. 
Our test dataset is about 200,000 roads.  Both mapserver and
PostGIS/postgres are running on the same machine.
To make a map of a very small area (about 25 roads), it takes about 0.25
seconds using PostGIS and about 0.1 seconds using shapefiles.
To make a map of all the 200,000 roads, its takes about 4.5 seconds
using PostGIS and about 1.3 seconds using shapefiles.

The process works as:
<PostGIS query> -> <Convert to WKB> -> <Transmit to mapserver> ->
<Convert to mapserver format>
There should be lots of places to do some optimizations.

I just came back from a holiday, and paul is still away on holiday, so
it'll be a while before I can get it all wrapped up nicely, tested, and
get a proper configure script.  Once thats done, we'll make a release. 
If anyone out there can help with the "./configure" script, we'd really
appreciate it.
If you want to see the current version, I'd be happy to tar it up and
send it out to you.

dave
ps. thanks to Daniel Morissette and the other authors (Frank
Warmerdam???) of mapogr.cpp for writing easy-to-understand code.  And
to Stephen Lime for explaining the zen of maplayer.c.

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