[Qgis-developer] have aggregate/window expressions ever been discussed?
giohappy at gmail.com
Tue May 27 06:40:06 PDT 2014
I agree with all of you about not reinventing the wheel and, yes, let's not
fragment QGIS' capabilities on data querying/filtering/etc.
My first idea was simply (but I'm not sure how much simple it is) to be
able to perform aggregate queries like in WINDOW functions. In my job it's
something I find very useful, and I would like not to have to export my
layers to a PostGIS DB just to do it.
Some basic examples:
- get the average area of some polygon features
- get the relative dimension against some other feature's dimensions
AFAIK these kind of queries cannot be run on Sqlite in one single shot.
This is why I wasn't thinking to Sqlite (or SQL anyway) to implement it,
but as an extension to expression engine, in a MapReduce pattern
2014-05-27 15:03 GMT+02:00 Régis Haubourg <
regis.haubourg at eau-adour-garonne.fr>:
> Hugo Mercier wrote
> > Or
> >> calculated fields in view can't be explicitly cast, so QGIS should have
> >> to
> >> guess data type based on a data scan (a major unadressed issue of
> > Hmmm I wasn't aware of this limitation in SQLITE views :(
> Yes, SQLITE does dynamic typing, so user or provider has to scan values to
> guess the right type.
> Here is a sqlite topic on that 
> And here my initial post in qgis list 
> View this message in context:
> Sent from the Quantum GIS - Developer mailing list archive at Nabble.com.
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