[Qgis-developer] have aggregate/window expressions ever been discussed?

[Hugo Mercier]

Le 27/05/2014 16:09, G. Allegri a écrit :
>     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.
>  

Exactly.

But we have to discuss the technical details :)
What we've been building so far is some in-house implementation of a
partial database engine. And when we want to add more new powerful
features, then ... what we have is too limited.
So the idea is to use a "real" database engine to deal with everything
that is related to a database AND to be transparent for most of the
users. So yes, the objective, in my opinion is to keep existing GUI
parts and always have end-users in mind when adding a new feature (like
aggregation).

So yeah, the challenge is how to use SQLite as the underlying engine,
when the user inputs QgsExpressions or don't want to have anything to do
with SQLite (part of the answer should be to have an expression to SQL
converter, indeed)