[jboss-jira] [Red Hat JIRA] (DROOLS-5697) Make exec model's groupBy() composable

Make exec model's groupBy() composable -------------------------------------- Key: DROOLS-5697 URL: https://issues.redhat.com/browse/DROOLS-5697 Project: Drools Issue Type: Enhancement Components: executable model Affects Versions: 7.44.0.Final Reporter: Lukáš Petrovický Assignee: Mario Fusco Priority: Major In some of the OptaPlanner examples, we have Constraint Streams like this: {code:java} .groupBy(ProcessAssignment::getService, count()) .groupBy(Service::getTag, max((service, count) -> count)) {code} This will: - Take all ProcessAssigment instances. - Count all such instances which run on the same Service. - Out of all the pairs of (service, count) find the maximum count where the services share the same Tag. This is an example of groupBy composition. Currently, we implement it with the old, inefficient groupBy. That implementation looks something like this: {noformat} when $tuples: List<Tuple<Service, Integer>> from accumulate( $p: ProcessAssignment(), ... groupBy(ProcessAssignment::getService, count()) ) $tuples2: List<Tuple<String, Integer>> from accumulate( $tuple: Tuple<Service, Integer> from $tuples, ... groupBy(Service::getTag, max($tuple._2)) ) $result: Tuple<String, Integer> from $tuples2 then System.out.println($result); end {noformat} We'd like the new groupBy construct to be capable of composition instead.