[QGIS-Developer] Processing 3.0: Dropping the 'Select by attribute sum' alg?

[Nyall Dawson]

Hi all,

I'd like to propose that in processing in QGIS 3.0 we drop the 'Select
by Attribute Sum' algorithm. As you're probably aware we've been
cleaning up and streamlining the preinstalled algorithms that are
provided with QGIS, and I think this algorithm is a good candidate for
removal.

(For clarification: this algorithm takes an input vector layer, field
selection and numeric value. It requires a single selected feature is
present in the input layer. It then loops through all neighbouring
features and 'dissolves' them into the selected feature. As soon as
the total attribute sum for all dissolved features exceeds the entered
value, the algorithm is complete)

My thoughts are:
- The use case for this algorithm is very unclear for users - the name
does not describe what the algorithm does, and there's no help
documentation available for the algorithm either. Given this I suspect
that the algorithm is not being put into use.
- The algorithm needs enhancement to be more useful. There's no logic
in place which dictates how neighbouring features are chosen to
dissolve into the selected feature (it's effectively random - you're
just as likely to get a huge narrow polygon stretching across a map as
you are a nice compact cluster). To be more useful the algorithm would
need logic to either minimise the area of the dissolved feature, or
minimise the total number of dissolved features, or ... ?

I think this algorithm should be moved to a processing plugin until
it's matured and had these shortcomings addressed.

Any thoughts?

Nyall