[GRASS-dev] [GRASS GIS] #516: v.extract slow on large datasets

GRASS GIS trac at osgeo.org
Tue Mar 3 18:08:28 EST 2009

#516: v.extract slow on large datasets
 Reporter:  gisboa       |       Owner:  grass-dev at lists.osgeo.org
     Type:  enhancement  |      Status:  new                      
 Priority:  minor        |   Milestone:  6.4.0                    
Component:  Vector       |     Version:  unspecified              
 Keywords:               |    Platform:  All                      
      Cpu:  All          |  
 Using v.extract on large datasets is incredibly slow. From a 3,000,000
 areas dataset I extracted the first 99 (id<100). It took 12 minutes to
 extract the geometries, after that it says 'writing attributes' for
 another 6 minutes. The pg process is a runner-up in top, consuming about
 50% cpu time, the remaing 50% goes to v.extract.
 What is going on here? Writing a hundred rows to PostgreSQL should take
 only a split second. Is this also due to the fact that the geometry index
 is not in a file? Would this be another reason to implement the file based
 geometry index?
 Maybe a few modules should be rewritten to perform a dedicated task on
 their own, instead of relying on others, if that makes it slow.

Ticket URL: <http://trac.osgeo.org/grass/ticket/516>
GRASS GIS <http://grass.osgeo.org>

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