Contstraint stream breaks when switching from OptaPlanner 7.46.0 to 8.0.0 - constraints

Question

I have a constraint that crashes in the latest OptaPlanner 8.0.0, but used to work fine on 7.46.0.
As expected, IntelliJ's code inspection (and the debugger) shows that after the first join, the stream is a TriConstraintStream. The runtime class makes more sense to me than the class OptaPlanner is trying to cast to.
When leaving out the last groupBy the error goes away, so that clause seems to cause the issue.
Did something change in the way join and groupby worked?
It seems that the underlying OptaPlanner code was refactored for 8.0.0, so I have trouble seeing what exactly changed in OptaPlanner.
Should I add something to ensure that a TriJoin is used instead of a BiJoin?
I could not find any relevant notes in the migration documentation.
protected Constraint preventProductionShortage(ConstraintFactory factory) {
return factory.from(Demand.class)
.groupBy(Demand::getSKU,
Demand::getWeekNumber
)//BiConstraintStream
.join(Demand.class,
equal((sku, weekNumber)-> sku, Demand::getSKU),
greaterThanOrEqual((sku, weekNumber)-> weekNumber, Demand::getWeekNumber)//TriConstraintStream
)
.groupBy((sku, weekNumber, totalDemand) -> sku,
(sku, weekNumber, totalDemand) -> weekNumber,
sum((sku, weekNumber, totalDemand) -> totalDemand.getOrderQuantity())
)//TriConstraintStream
.penalize("Penalty", HardMediumSoftScore.ONE_MEDIUM,
(sku_weekNumber, demandQty, productionQty) -> 1);
}
Stack trace:
java.lang.ClassCastException: class org.optaplanner.core.impl.score.stream.tri.CompositeTriJoiner cannot be cast to class org.optaplanner.core.impl.score.stream.bi.AbstractBiJoiner (org.optaplanner.core.impl.score.stream.tri.CompositeTriJoiner and org.optaplanner.core.impl.score.stream.bi.AbstractBiJoiner are in unnamed module of loader 'app')
at org.optaplanner.core.impl.score.stream.drools.common.rules.BiJoinMutator.<init>(BiJoinMutator.java:40)
at org.optaplanner.core.impl.score.stream.drools.common.rules.UniRuleAssembler.join(UniRuleAssembler.java:70)
at org.optaplanner.core.impl.score.stream.drools.common.rules.AbstractRuleAssembler.join(AbstractRuleAssembler.java:179)
at org.optaplanner.core.impl.score.stream.drools.common.ConstraintSubTree.getRuleAssembler(ConstraintSubTree.java:94)
at org.optaplanner.core.impl.score.stream.drools.common.ConstraintSubTree.getRuleAssembler(ConstraintSubTree.java:89)
at org.optaplanner.core.impl.score.stream.drools.common.ConstraintGraph.generateRule(ConstraintGraph.java:431)
at org.optaplanner.core.impl.score.stream.drools.common.ConstraintGraph.lambda$generateRule$57(ConstraintGraph.java:423)
at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195)
at java.base/java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948)
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:913)
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:578)
at org.optaplanner.core.impl.score.stream.drools.common.ConstraintGraph.generateRule(ConstraintGraph.java:424)
at org.optaplanner.core.impl.score.stream.drools.DroolsConstraintFactory.buildSessionFactory(DroolsConstraintFactory.java:101)
at org.optaplanner.core.impl.score.director.stream.ConstraintStreamScoreDirectorFactory.<init>(ConstraintStreamScoreDirectorFactory.java:77)
at org.optaplanner.test.impl.score.stream.DefaultConstraintVerifier.verifyThat(DefaultConstraintVerifier.java:63)
at org.optaplanner.test.impl.score.stream.DefaultConstraintVerifier.verifyThat(DefaultConstraintVerifier.java:32)
at com.ohly.planner.constraints.ConstraintsTest.weekShortageSingleSKU(ConstraintsTest.java:61)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53)
Process finished with exit code -1
[edit] For completeness, the new function as suggested by Lukáš Petrovický
protected Constraint preventProductionShortage(ConstraintFactory factory) {
return factory.from(Demand.class)
.join(Demand.class,
equal(Demand::getSKU),
greaterThanOrEqual(demand -> demand.getWeekNumber()))
.groupBy((d, d2) -> d.getSKU(),
(d, d2) -> d.getWeekNumber(),
sum((d,d2) -> d2.getOrderQuantity())
)
...
[/edit]

Answer 1

This was an unfortunate bug not caught by the existing test coverage.
The fix is aimed at OptaPlanner 8.0.1, incl. test coverage improvement.
That said, I would argue that the constraint is not very efficient. Unless I'm missing some key implications, the following is semantically very similar, yet much faster:
protected Constraint preventProductionShortage(ConstraintFactory factory) {
return factory.from(Demand.class)
.join(Demand.class,
equal(Demand::getSKU),
greaterThanOrEqual(demand -> demand.getWeekNumber()))
.groupBy(..., ..., sum((demand, demand2) -> ...))
.penalize("Penalty", HardMediumSoftScore.ONE_MEDIUM);
}
Note how I eliminated the first use of groupBy(). There may be some difference though in how many tuples are penalized this way, which may or may not be what you want. Feel free to open another question on that.