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

[Martin Dobias]

On Tue, May 27, 2014 at 4:21 PM, Vincent Picavet
<vincent.ml at oslandia.com> wrote:
> 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 wheel,
> 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, lacking
> coherency.

Agreed.

In addition to the features mentioned above, I believe also indexing
and caching of vector data could be handled by SQLite, so it would be
good to keep that in mind during the design. Finally, the "memory"
provider could be implemented on top of in-memory SQLite table, too.

Regards
Martin