[GRASS-dev] [GRASS GIS] #859: v.patch: category abuse

[GRASS GIS]

#859: v.patch: category abuse
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 Reporter:  hamish   |       Owner:  grass-dev at lists.osgeo.org
     Type:  defect   |      Status:  new                      
 Priority:  normal   |   Milestone:  6.4.1                    
Component:  Vector   |     Version:  svn-develbranch6         
 Keywords:  v.digit  |    Platform:  Linux                    
      Cpu:  x86-64   |  
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 Hi,

 I am trying to patch together a couple hundred individual lines into a
 single map. Each line has been given a unique category number so that when
 their (identical) tables are merged they will not conflict.

 after creating an empty vector with v.in.ascii and creating a matching
 table for it, the patch loop looks like this:
 {{{
 for MAP in `g.mlist vect pattern="track_*"` ; do
    v.patch -a -e in="$MAP" out=tracks --overwrite --quiet
 done
 }}}

 g.mlist+v.db.select for some input maps:
 {{{
 cat|filename
 10101|M02-001-0101
 10224|M02-001-0224
 10346|M02-001-0346
 12305|M02-001-2305
 20044|M02-002-0044
 20209|M02-002-0209
 20333|M02-002-0333
 20458|M02-002-0458
 20650|M02-002-0650
 20813|M02-002-0813
 20944|M02-002-0944
 21112|M02-002-1112
 21253|M02-002-1253
 21434|M03-002-1434
 21557|M03-002-1557
 21721|M03-002-1721
 21854|M03-002-1854
 }}}

 v.db.select for v.patch output:
 {{{
 cat|filename
 10102|M02-001-0101
 20327|M02-001-0224
 30674|M02-001-0346
 42980|M02-001-2305
 63025|M02-002-0044
 83235|M02-002-0209
 103569|M02-002-0333
 124028|M02-002-0458
 144679|M02-002-0650
 165493|M02-002-0813
 186438|M02-002-0944
 207551|M02-002-1112
 228805|M02-002-1253
 250240|M03-002-1434
 271798|M03-002-1557
 293520|M03-002-1721
 315375|M03-002-1854
 }}}

 you can see that the category value in the output patch becomes:
 {{{
  1 + map1
  1 + map1 + 1 + map2
  1 + map1 + 1 + map2 + 1 + map3
  .
  .
  .
 }}}

 how to make max_cat() or what ever is doing it stop?

  * I cannot guarantee that input maps arrive sorted by cat, smallest to
 largest.
  * It has to check if the cat is already used, if so it has to decide what
 to do with existing database attributes. Probably exit with a fatal error.
  * I suppose this needs a flag: you either care to preserve the cat but
 accept fatal errors and a small time penalty; or you don't mind
 reassigning cats to avoid fatal errors.


 thanks,
 Hamish

-- 
Ticket URL: <https://trac.osgeo.org/grass/ticket/859>
GRASS GIS <http://grass.osgeo.org>