[GRASS-dev] Separate sqlite database files for vector maps

[Markus Metz]

On Sat, Sep 10, 2016 at 5:33 PM, Markus Metz
<markus.metz.giswork at gmail.com> wrote:
> On Fri, Sep 9, 2016 at 11:06 PM, Sören Gebbert
> <soerengebbert at googlemail.com> wrote:
>> Dear devs,
>> i would like to implement sqlite database support as separated file for each
>> vector map. Similar to the dbf approach but with sqlite. Other databases are
>> no option in my case.
>> The reasons for this approach are the following:
>>
>> * The temporal vector algebra would hugely benefit from separated sqlite
>> vector map files, since it can compute in parallel, no race condition or
>> serial processing of database requests is required
>> * Vector maps can easily be moved between locations with full database
>> content, no data loss. Simply the vector map directory must be archived
>> * Merging of mapsets is much easier, since the vector map sqlite databases
>> don't need to be merged, only copied
>>
>> This approach would be implemented in addition to all other existing
>> approaches.
>>
>> However, i don't know were to start with this, any hints or suggestions?
>
> This is implemented in G6.3, maybe also early versions of G6.4, but
> has been removed at some stage, no idea why.
> Have a look at lib/vector/Vlib/field.c, there at the fns
> Vect_subst_var()
> and
> Vect_get_dblink()
>
> Essentially, all that is needed is a corresponding entry in $LOCATION_NAME/VAR:

in $LOCATION_NAME/$MAPSET/VAR:

> instead of
> DB_DRIVER: sqlite
> DB_DATABASE: $GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db
>
> try
> DB_DATABASE: $GISDBASE/$LOCATION_NAME/$MAPSET/vector/$MAP/sqlite/sqlite.db
>
> HTH,
>
> Markus M