[
https://issues.apache.org/jira/browse/CALCITE-2223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16751646#comment-16751646
]
Vladimir Sitnikov commented on CALCITE-2223:
--------------------------------------------
[~vvysotskyi], thanks!
I guess the problem is VolcanoPlanner allows cycles in the rel nodes.
When a single cycle appears, then various rules can pump it by innocent things
like FilterProjectTranspose.
I've debugged TestProjectWithFunctions.testCastFunctions a bit, and my
understanding is the activated rules are sound, and the problem is that
TestProjectWithFunctions.testCastFunctions tricks VolcanoPlanner into creating
a cycle between RelSubsets.
Note: FilterProjectTranspose sees just 2-3 rel nodes (Filter, Project, and
project's input), and it might fail to see that the rule it is operating on a
part of a cycle.
So I guess we should ban cycles at equivalence registration time (and at relset
merge).
If RelSets are kept acyclic at all times, then we won't hit "infinite
cast(cast(cast(...)))) kind of rule applications".
I'll try an approach like "mark relnode unusable in case its addition forms a
cycle".
Of course it might impose problem for "materialization via union", however I
guess Volcano is supposed to operate on DAGs, so it would anyway require
special treatment (e.g. {{@Ignore}} for now).
[~julianhyde], any thoughts?
> 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: 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}
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
