[Qgis-developer] have aggregate/window expressions ever been discussed?
giohappy at gmail.com
Tue May 27 07:09:22 PDT 2014
> We will need these aggregate functions in forms for information purposes
> and in the print composer for generating reports. Having to write
> Postgis-Views would work for database pros. But let's not forget that
> not all of our users are database professionals and not all of the users
> have their data in Postgis.
> Personally, I don't care where these aggregate functions are implemented
> and executed, as long as they are easy to use and do not enforce the
> usage of a specific data format.
I totally agree Andreas.
Whatever the way it would be implemented, I hope it won't become a blank
textarea where to write some "special" SQL.
I imagine something integrated into the rest of expressions GUI.
> Am 27.05.2014 09:21, schrieb Vincent Picavet:
> > Hello Andreas,
> > Le mardi 27 mai 2014 10:28:13, Andreas Neumann a écrit :
> >> Hi,
> >> We would definitely need this functionality for our application modules
> >> - we need functions like "min", "max", "mean", "sum", "average" to work
> >> on 1:n relations.
> >> Now that we have relations in QGIS, I think that aggregate functions are
> >> a logical next step. Something to seriously consider in 2.6.
> > As already stated before, I am worrying about current developments
> around a
> > lot of features looking like database features :
> > * Table joins
> > * relations
> > * "SQL-like" processing
> > * .. including aggregates
> > Implementing all these features on top of QGIS seems reinventing the
> > and database wheels are particularly hard to design and implement well.
> > I really think we should re-study the global design of such features to
> have a
> > clear and clean strategy instead of stacking features on features,
> > coherency.
> > As stated by Regis, basing this work on top of SQLite may be the best
> > but more study has to be done and a general agreement is needed to go
> > way.
> > Vincent
> >> Andreas
> >> Am 23.05.2014 17:34, schrieb G. Allegri:
> >>> Recently I had to calculate the relative dimension of a polygon
> >>> to the others of the same class. I know there are a lot of way to do
> >>> inside and outside QGIS, but I wondered if field calculator (and
> >>> expressions in general) couls be extended to accompish this kind of
> >>> tasks.
> >>> The approach would be something similar WINDOW functions in Postgresql
> >>> , where for each record a new value will be calculated on the basis
> >>> of other records (filtered or not).
> >>> Has this ever been discussed? Is it something that could fit QGIS
> >>> expressions?
> >>> giovanni
> >>>  http://www.postgresql.org/docs/9.1/static/tutorial-window.html
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