[GRASS-dev] [GRASS GIS] #1798: all relevant vector modules should have cats and where parameters

[GRASS GIS]

#1798: all relevant vector modules should have cats and where parameters
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 Reporter:  mlennert              |       Owner:  grass-dev@…              
     Type:  enhancement           |      Status:  new                      
 Priority:  normal                |   Milestone:  7.0.0                    
Component:  Vector                |     Version:  svn-trunk                
 Keywords:  where cats parameter  |    Platform:  Unspecified              
      Cpu:  Unspecified           |  
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Comment(by mmetz):

 Replying to [comment:1 glynn]:
 > Replying to [ticket:1798 mlennert]:
 > > A series of vector modules should have cats and where parameters
 allowing the user to apply the operation only on selected features. Having
 this options avoids having to create many intermediate maps. And for a
 more homogeneous user experience it would be nice to have them in all
 modules, unless irrelevant.
 >
 > Would it be feasible (and desirable) to allow the creation of "views"
 (virtual maps which obtain their data from an underlying map), similar to
 v.external or raster "reclass" maps?

 Technically, this would be possible, but it would require quite a few
 changes to the vector libs. Essentially, constraints would need to be
 implemented, similar to OGR filtering options.

 IIUC, these virtual maps should behave just like normal maps: from a user
 perspective, it could look like
 {{{
 r.extract -v (-v as new flag to create a view or virtual vector)
 v.buffer
 }}}

 instead of
 {{{
 r.extract
 v.buffer
 }}}

 Disk space consumption would be lower for virtual maps, but so would be
 processing speed when working with a virtual map. I would rather go for
 processing speed.

 Markus M

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Ticket URL: <http://trac.osgeo.org/grass/ticket/1798#comment:4>
GRASS GIS <http://grass.osgeo.org>