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https://issues.apache.org/jira/browse/CALCITE-2223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16753391#comment-16753391
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Volodymyr Vysotskyi commented on CALCITE-2223:
----------------------------------------------
Yes, that's correct, ignored {{UnionExchangePrel}} instance is created using
converter.
> ProjectMergeRule is infinitely matched when is applied after
> ProjectReduceExpressionsRule
> -----------------------------------------------------------------------------------------
>
> Key: CALCITE-2223
> URL: https://issues.apache.org/jira/browse/CALCITE-2223
> Project: Calcite
> Issue Type: Bug
> Reporter: Volodymyr Vysotskyi
> Assignee: Julian Hyde
> Priority: Critical
> Attachments:
> TestLimitWithExchanges_testPushLimitPastUnionExchange.png, heap_overview.png,
> provenance_contents.png
>
>
> For queries like this:
> {code:sql}
> select t1.f from (select cast(f as int) f, f from (select cast(f as int) f
> from (values('1')) t(f))) as t1
> {code}
> OOM is thrown when {{ProjectMergeRule}} is applied before applying
> {{ProjectReduceExpressionsRule}} in VolcanoPlanner.
> A simple test to reproduce this issue (in {{RelOptRulesTest}}):
> {code:java}
> @Test public void testOomProjectMergeRule() {
> RelBuilder relBuilder =
> RelBuilder.create(RelBuilderTest.config().build());
> RelNode relNode = relBuilder
> .values(new String[]{"f"}, "1")
> .project(
> relBuilder.alias(
> relBuilder.cast(relBuilder.field(0), SqlTypeName.INTEGER),
> "f"))
> .project(
> relBuilder.alias(
> relBuilder.cast(relBuilder.field(0), SqlTypeName.INTEGER),
> "f0"),
> relBuilder.alias(relBuilder.field(0), "f"))
> .project(
> relBuilder.alias(relBuilder.field(0), "f"))
> .build();
> RelOptPlanner planner = relNode.getCluster().getPlanner();
> RuleSet ruleSet =
> RuleSets.ofList(
> ReduceExpressionsRule.PROJECT_INSTANCE,
> new ProjectMergeRuleWithLongerName(),
> EnumerableRules.ENUMERABLE_PROJECT_RULE,
> EnumerableRules.ENUMERABLE_VALUES_RULE);
> Program program = Programs.of(ruleSet);
> RelTraitSet toTraits =
> relNode.getCluster().traitSet()
> .replace(0, EnumerableConvention.INSTANCE);
> RelNode output = program.run(planner, relNode, toTraits,
> ImmutableList.<RelOptMaterialization>of(),
> ImmutableList.<RelOptLattice>of());
> // check for output
> }
> /**
> * ProjectMergeRule inheritor which has
> * class name greater than ProjectReduceExpressionsRule class name
> (String.compareTo()).
> *
> * It is needed for RuleQueue.popMatch() method
> * to apply this rule before ProjectReduceExpressionsRule.
> */
> private static class ProjectMergeRuleWithLongerName extends
> ProjectMergeRule {
> public ProjectMergeRuleWithLongerName() {
> super(true, RelFactories.LOGICAL_BUILDER);
> }
> }
> {code}
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