optaplanner - groupBy with 3 ConstraintCollectors?

Question

I like to schedule observations of variable duration (planning entity) into hourly time slots over several nights. I would need to impose that there are no gaps in particular groups, and need collectors for minimum, maximum and sum. Is there a workaround to have a groupBy with one groupKeyMapping and three collectors?

constraintFactory.from(OB.class)
    .groupBy(OB::getGroupID, min(OB::getStart), max(OB::getEnd), sum(OB::getDuration))

I tried to workaround this using toList() and computing values myself but strangely it doesn't pass down a List<OB> but single OBs. The code below prints class my.package.OB

constraintFactory.from(OB.class)
   .groupBy(OB::getGroupID, toList())
   .filter((groupID, entries) -> {
       println "=> ${entries.class} "
       return true
   })

question from:https://stackoverflow.com/questions/65928663/groupby-with-3-constraintcollectors

Answer 1

This was a gap in our API (see PLANNER-2330). It is being addressed for OptaPlanner 8.3.0. We encourage you to upgrade - not only to get this particular feature, but also some nice performance improvements, assuming you're using higher cardinality joins.