Error when passing hepPlanner to

[Val]

Hi guys,

I am trying to make the Prepare.optimize() method run faster:
https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/prepare/Prepare.java

According to this article: https://calcite.apache.org/docs/adapter.html :
"Calcite has two built-in planner engines: class VolcanoPlanner uses
dynamic programming and is good for exhaustive search, whereas class
HepPlanner fires a sequence of rules in a more fixed order."

So, I've figured that I can use HepPlanner, because speed is important to
me, so I can use less exhaustive but faster search.

I've added a HepPlanner:
    final HepProgramBuilder programBuilder = HepProgram.builder();
    programBuilder.addMatchOrder(HepMatchOrder.ARBITRARY);
    programBuilder.addRuleInstance(UnionMergeRule.INSTANCE);
    HepPlanner hepPlanner = new HepPlanner(programBuilder.build());
    hepPlanner.setRoot(root.rel);
    RelNode hepRoot = hepPlanner.findBestExp();
    RelRoot hepRelroot = root.withRel(hepRoot);

Then I pass this planner into the run() call (substituted "planner" with
"hepPlanner"):
    final RelNode rootRel4 = program.run(
         hepPlanner, hepRelroot.rel, desiredTraits, materializationList,
latticeList);

When running unit tests I get exception:

java.lang.StackOverflowError
                at java.security.AccessController.doPrivileged(Native
Method)
                at java.io.PrintWriter.<init>(PrintWriter.java:116)
                at java.io.PrintWriter.<init>(PrintWriter.java:100)
                at
org.apache.calcite.rel.AbstractRelNode.computeDigest(AbstractRelNode.java:396)
                at
org.apache.calcite.rel.AbstractRelNode.recomputeDigest(AbstractRelNode.java:356)
                at
org.apache.calcite.plan.hep.HepPlanner.addRelToGraph(HepPlanner.java:817)
                at
org.apache.calcite.plan.hep.HepPlanner.applyTransformationResults(HepPlanner.java:741)
                at
org.apache.calcite.plan.hep.HepPlanner.applyRule(HepPlanner.java:559)
                at
org.apache.calcite.plan.hep.HepPlanner.depthFirstApply(HepPlanner.java:370)
                at
org.apache.calcite.plan.hep.HepPlanner.depthFirstApply(HepPlanner.java:382)
                …<many more lines like this>
                at
org.apache.calcite.plan.hep.HepPlanner.depthFirstApply(HepPlanner.java:382)

Let me know what I am doing wrong. I've tried skipping the call to run()
method, but just using the HepPlanner alone with the newly added code shown
above doesnt generate physical plan. Is there a way to use HepPlanner so
that it generates physical plan?

Thanks,
Val