[Qgis-developer] Thoughts about multi-type tables in QGIS

[Olivier Dalang]

>
>  I think that we end up defining different symbols for different
> geometries anyway


That's not completely true. The main color could be shared across all
geometry types. The point style could be used by linestrings and polygons
nodes. The linestring style could be used by the polygon edges. It's more
or less how Leaflet does it, and it works fairly well.



> to me it sounds a bit like loading "varchar" and "float" in the same column


That's exactly what it is not. Generic geometry is a valid and well defined
type, and postgis functions behave very well with it. ST_Area for instance
will return 0 for a point or a line, which is an accurate result and makes
sense.
And while some functions are type-specific, most functions work and make
sense on all types (spatial relations, buffer, bounding boxes, validity,
transformation, simplification, conversion...).

If you split your data in different tables (or columns), you loose the
ability to use any of those functions on all your records at once (without
some complex query that won't be doable in QGIS UI), which IMO is really a
pity...



2015-04-07 13:21 GMT+02:00 Roy <royroge at outlook.com>:

>
>
> Il 07/04/2015 11.55, Olivier Dalang ha scritto:
>
>   *Event data management*
> I have a postgis table for historical events, which can be of any
> geometrical type.
> The events can have links to other events (using references like
> previous_event_id).
> Currently, I have to add the postgis table four times. Once for each
> geometry type, plus once as a no-geometry table so that I can have the full
> attribute table to be able to use the relations widget.
> At this point, every setting (filtering, labels, actions, symbols...) must
> be made four times,
>
>
> In general I think that we end up defining different symbols for different
> geometries anyway, i do not see how a point and an area can have the
> same simbology; also there are specific postgis functions that make sense
> to use for specific geometry (i.e. ST_Area).
> I do not want to say that i'm against the idea of mixing geometries, but
> to me it sounds a bit like loading "varchar" and "float" in the same column
> and eventually ending introducing more complications than benefits, just
> my opinion,
>
> best, Roy.
>
>
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