[GRASS-user] RE: Problem querying layers other than '1' in gi s.m

Radim Blazek radim.blazek at gmail.com
Wed Sep 27 04:44:07 EDT 2006

On 9/27/06, Trevor Wiens <twiens at interbaun.com> wrote:
> On Tue, 26 Sep 2006 17:06:13 +0200
> Radim Blazek wrote:
> ---snip---
> >
> > In theory you could move the relations to a database as suggested Trevor,
> > but it would be difficult and not efficient to reflect any operations
> > on geometry in database.
> >
> > It is very easy to assign 2 cats to the overlapping parts
> > from 2 input areas, to do that in database (from GRASS) is much more complex.
> > If you want, you have to move to database everything, i.e. also geometry.
> I completely disagree. It would be very easy to describe overlapping
> areas with database attributes, in fact, IMO much easier than with
> layers. You are correct however, that storing this information
> internally in GRASS is more efficient for the very small percent of the
> time where a module will need to reference this information for some
> purpose other than getting a list of objects to consider for
> processing. Right now almost all modules allow for some filtering by a
> query so AFAICT using arbitrary queries to replace the 'layers feature'
> would have a negligible impact on performance in most cases. If this is
> not the case please elaborate.
> It does not follow that moving attribute management into the database
> requires the movement of geometry as well, or at least you've not
> demonstrated it, only stated it.

Try to rewrite v.overlay using your model.


> T
> --
> Trevor Wiens
> twiens at interbaun.com
> The significant problems that we face cannot be solved at the same
> level of thinking we were at when we created them.
> (Albert Einstein)

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