I have been setting up a PostGIS database with the boundary files
from Census Canada. There are a number of invalid geometries, either
Self-intersection at or near point X, Y or Ring Self-intersection at
or near point X, Y, especially for the year 2006. For most of the
files, the cleangeometry() function as found at
http://www.sogis1.so.ch/sogis/dl/postgis/cleanGeometry.sql
created by Duster Horst with suggestions by Kevin Neufeld
(http://www.mail-archive.com/[email protected]/msg03531.html)
cleans the invalid geometries up (although I haven't checked them for
errors such as those Kevin talked about). However, for several
geometries, the process runs for a very long time and the cpu use is
listed as 100% from running top. One process I even left running
for 2 days before killing it. Also, it seems that even after the
cleaning of these geometries is successful, requests such as "SELECT
* FROM table WHERE NOT ST_ISVALID(the_geom);" take a long time to
complete and are listed as using 100% of the CPU while they run.
Can anyone shed any light on why this might be?
I was also interested in why some of the function calls in the
cleangeometry() function do not have the "ST_" prefix in front of
them. Is there any difference between a call to boundary and
st_boundary, for example, in Postgis 1.4 or 1.5. I am running this
on Ubuntu LINUX with PostgresPlus 8.4SS from EnterpriseDB, since I
always set the path as PATH=/opt/PostgresPlus/8.4SS/bin. This is with
Postgis 1.4, I believe, although it looks like someone else on the
machine has also enabled postgis 1.5 in the synaptic package manager.
Thanks,
Loretta
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