[GRASS-dev] [GRASS GIS] #2258: t.create creates DB always in the PERMANENT

[GRASS GIS]

#2258: t.create creates DB always in the PERMANENT
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 Reporter:  martinl      |       Owner:  grass-dev@…              
     Type:  defect       |      Status:  new                      
 Priority:  normal       |   Milestone:  7.0.0                    
Component:  Temporal     |     Version:  unspecified              
 Keywords:  t.register   |    Platform:  Unspecified              
      Cpu:  Unspecified  |  
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Comment(by huhabla):

 Replying to [comment:4 glynn]:
 > Replying to [comment:3 huhabla]:
 >
 > > There is a reason why the temporal database is generated and used by
 default in the PERMANENT directory.
 >
 > Does it handle the case where the user lacks the filesystem permissions
 to write to PERMANENT?

 There is no explicit error handling implemented. The creation process will
 terminate with a Python exception.

 >
 > Does it handle race conditions, i.e. where two users both try to create
 the database at the same time?

 No. How does GRASS handle the race condition in case two user try to
 create a mapset with the same name at the same time?

 >
 > Ordinarily, we assume that the user lacks write permission outside their
 mapset.

 The temporal framework supports two SQL database backends: sqlite and
 postgresql. Sqlite is the default backend that can be used in case of
 single user GRASS locations. In case of a multi-user GRASS environment the
 postgresql database backend should be used instead, since it is able to
 handle concurrent read/write and multi-user access better than sqlite. The
 postgresql connection must be set explicitly with t.connect for each
 mapset, since temporal database connections are mapset specific.

 I absolutely prefer to use mapset specific sqlite database by default that
 will merge at runtime with temporal databases from other mapsets to avoid
 race conditions and filesystem permission problems. But unfortunately the
 Python sqlite implementation does not support the merge of different
 sqlite databases at runtime. Other file based databases were no option,
 because of the lack of time support, or Python support and the
 introduction of additional dependencies. Therefore the postgresql support
 to avoid some problems of the sqlite backend.

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Ticket URL: <http://trac.osgeo.org/grass/ticket/2258#comment:5>
GRASS GIS <http://grass.osgeo.org>