[postgis-users] GEOS union() error

Kevin Neufeld kneufeld at refractions.net
Tue Nov 6 14:49:32 PST 2007


Lee Keel wrote:
> Well that got me past that error, but now I have a much bigger problem.  I
> need a way to speed up the geomunion process.  I know I am asking a lot of
> this function, but I have about 40K rows and the process to do the geomunion
> has been running over 80 mins and still going.  Does anyone have a better
> idea on how I can get the same results?  
>   
Just a thought here, but I don't think you need to use geomunion at 
all.  Try just collecting them together and then buffering your collection.

select buffer(collect(the_geom), 400) as the_geom from main;

Also, I don't know if this will help you since you're not really 
performing any joins, but ...
Since you're attempting to do this all at once, if you have the memory, 
I would make sure your work_mem is temporarily set as high as you can.
-- ie. this will temporarily set the amount of memory postgres can use 
for the duration of your session to 1.2GB (the default is 1MB)
SET work_mem TO 1200000;

-------------
Kevin Neufeld
Software Developer
Refractions Research Inc.
300-1207 Douglas St.
Victoria, B.C., V8W 2E7

Phone: (250) 383-3022
Email: kneufeld at refractions.net




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