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
I just tried this in JTS via JEQL. Timing for the union was 4 sec.
Any thoughts why PostGIS is about 40x slower than ArcMap at this
operation?
As Regina said, the current union operation in PostGIS is quite
inefficient. It should speed up a lot once the CascadedUnion algorithm
is implemented (which is what the above test in JTS uses)
ArcMap's time is impressive... since they're not open-source it's hard
to know what they're doing to get this kind of speed. 8^)
Any thoughts why Oracle takes 25 min? lol
Maybe for a truer metric you should multiply the time by the annual
license fee 8^) Of course, this doesn't help Oracle much...
--
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022
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