[postgis-users] PostGIS 1.3.3 on Windows XP Unstable

[Paragon Corporation]

Mike ,

I just tested this layer with a draft version of our new unioning approach.
- it completes in 10 seconds.  Not great but better than the current
ST_Union approach.

In OpenJump by the way which is using a not quite as sophisticated algorithm
as Martin's cascaded union, the below completes in 3 seconds.  So not to
worry - next version (1.3.4)  I'm sure we'll be much closer to ArcMap in
speed, and in version 1.4 - we might even beat ArcMap.

Martin,

 This is a much more simplified version of the dataset I gave you yesterday
to test with where your approach completed in 20 seconds  (with 2895
records).  This one doesn't choke openjump as the one I gave you does and
only has 273 records

Hope that helps,
Regina

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Yes, Java2D was able to perform a union on the geometries produced by
ST_SimplifyPreserveTopology() and it does the union relatively fast. 

The only thing I have found that beats Java2D is ArcGIS. In one test I did I
performed a union of the USGS state boundaries
(http://www.census.gov/geo/cob/bdy/st/st00shp/st99_d00_shp.zip). Here are
the results:

Oracle 11.1:	25 min
PostGIS 1.3.3:	42 sec
Java2D 1.5:		4 sec
ArcMap 9.2:		1 sec

Any thoughts why PostGIS is about 40x slower than ArcMap at this operation?

Any thoughts why Oracle takes 25 min? lol

The bottleneck in my application now looks to be
ST_SimplifyPreserveTopology(). I'm finding that it's often best to do
computation outside the database. However, one thing that Java2D is missing
is a polygon simplification function. I might look to see if Geotools has
one.

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