[Qgis-developer] Multiple geometry columns per layer

Nathan Woodrow madmanwoo at gmail.com
Thu Nov 29 06:06:34 PST 2012


Honestly I find that a pain in the neck, from a users point of view and
from a developer point of view.  From a users point of view you now have to
have a tools that supports styling points, regions, lines all at the same
time, it also makes processing harder because you have to check the
geometry type before doing certain operations.

>From a developer point of view I think it can make things hard because you
have to check feature by feature what kind geometry you are dealing with
before working on it, have you got a 0 length line or a point because
length of a point is 0?. At the moment we just open the layer, check the
type and select the correct methods.

MapInfo does this and I always found it caused more problems then it's
worth IMO.  Although postgres and spatialite support storing different
geometry types in the same table I have seen it as bad practice.  If you do
happen to have a layer with say regions and points for building footprints,
you can put the layer twice in the geometry_columns table with a different
geometry type and QGIS will pick it up as a different layer, then you can
just set the zoom levels on each layer.

They are my thoughts anyway.

- Nathan

On Thu, Nov 29, 2012 at 11:55 PM, Matthias Kuhn <matthias.kuhn at gmx.ch>wrote:

> Hi,
> Why is not more than one geometry column per layer supported? Would it be
> hard to support more than one geometry column (and set one as the default
> to be displayed)?
> It would certainly make some tasks easier and maybe could be used for
> level of detail, related to the current zoom level.
> There was recently a discussion on this list about spatialite as default
> layer type and spatialite would support this, as does postgres.
> Regards,
> Matthias
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