Jesus Camacho Rodriguez created CALCITE-2883:
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Summary: HepPlanner subprogram may loop till getting out of memory
Key: CALCITE-2883
URL: https://issues.apache.org/jira/browse/CALCITE-2883
Project: Calcite
Issue Type: Bug
Reporter: Jesus Camacho Rodriguez
Assignee: Jesus Camacho Rodriguez
Consider the following two hep programs.
Program 1:
{code}
final HepProgramBuilder programBuilder = new HepProgramBuilder();
programBuilder.addMatchOrder(HepMatchOrder.BOTTOM_UP);
programBuilder.addRuleInstance(JoinToMultiJoinRule.INSTANCE);
programBuilder.addRuleInstance(LoptOptimizeJoinRule.INSTANCE);
final HepProgram program = programBuilder.build();
{code}
Program 2:
{code}
final HepProgramBuilder programBuilder = new HepProgramBuilder();
final HepProgramBuilder subprogramBuilder = new HepProgramBuilder();
subprogramBuilder.addMatchOrder(HepMatchOrder.BOTTOM_UP);
subprogramBuilder.addRuleInstance(JoinToMultiJoinRule.INSTANCE);
subprogramBuilder.addRuleInstance(LoptOptimizeJoinRule.INSTANCE);
programBuilder.addSubprogram(subprogramBuilder.build());
final HepProgram program = programBuilder.build();
{code}
I would expect both programs to behave similarly. However, program 2 will loop
indefinitely. The reason is that {{HepPlanner}} subprogram execution loops if
subprogram generates any new expression.
https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/plan/hep/HepPlanner.java#L339
This does not seem right since planner can control exiting the program (and
thus, subprogram) depending on its own internal state and configuration
properties, e.g., match limit.
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