[postgis-devel] Another Data Point

[Obe, Regina]

Ah I think JTS was able to do this in about 40-50 seconds.  And my
version was able to beat out Kevin's nested by a small margin.  I'll
retest on mine.

So I think we still need work here.

I'm curious what would happen if I combined the algorithm I wrote with
the new ST_Union how things would fair.  In theory it should fair the
same, but I'm not really using Martin's cascaded union algorithm to the
letter.


-----Original Message-----
From: postgis-devel-bounces at postgis.refractions.net
[mailto:postgis-devel-bounces at postgis.refractions.net] On Behalf Of Paul
Ramsey
Sent: Wednesday, January 21, 2009 12:50 AM
To: PostGIS Development Discussion
Cc: lee.keel at uai.com
Subject: [postgis-devel] Another Data Point

Using the original sample set from Lee Keel,

With the old style ST_Union, 3 hours, 27 minutes:

uniontest=# select st_area(st_union(the_geom)) from sample_poly;
      st_area
--------------------
 0.0324039850011104
(1 row)

Time: 12419261.819 ms


With the new cascaded ST_Union, 4 minutes, 30 seconds, or 46 times
faster.

uniontest=# select st_area(st_union_fast(the_geom)) from sample_poly;
      st_area
--------------------
 0.0324039850054305
(1 row)

Time: 271618.181 ms


That's one nasty data set.

P.
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