[GRASS-dev] Re: [GRASS GIS] #672: v.distance -a with upload=to_attr and table= option: problems in table creation and value upload

[GRASS GIS]

#672: v.distance -a with upload=to_attr and table= option: problems in table
creation and value upload
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 Reporter:  mlennert     |       Owner:  grass-dev@…              
     Type:  defect       |      Status:  new                      
 Priority:  major        |   Milestone:  6.4.0                    
Component:  Vector       |     Version:  unspecified              
 Keywords:  v.distance   |    Platform:  Unspecified              
      Cpu:  Unspecified  |  
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Comment(by mlennert):

 Replying to [comment:2 mlennert]:
 >  When using an SQLite backend, the trouble seems to come from the fact
 that the same database and table are accessed twice. Maybe some playing
 around with db_close_database_shutdown_driver might help, but I haven't
 had the opportunity to play around with that. Anybody have any hints about
 this ?

 I can now confirm that this is a database locking issue. When doing


 {{{
 g.copy vect=myhosp,myhosp2
 cp $GISDBASE/$MAPSET/sqlite.db ~/
 v.db.connect -o myhosp2 driver=sqlite database=~/sqlite.db key=cat
 table=myhosp2
 v.distance from=myhosp to=myhosp2 upload=cat,dist,to_attr to_column=CANCER
 column=to_cat,dist,to_cancer table=distance_cancer
 }}}

 it works, i.e distance_cancer contains values in the to_cancer column.

 I would imagine that this kind of sqlite database locking will be a
 problem in other modules as well, so this probably needs a wider solution
 than just within this module. Anyone out there with enough experience with
 SQLite to attack this ? This is very important if SQLite is to become the
 default db backend...

 Moritz

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Ticket URL: <http://trac.osgeo.org/grass/ticket/672#comment:3>
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