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https://issues.apache.org/jira/browse/CALCITE-3376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16940621#comment-16940621
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Xiening Dai commented on CALCITE-3376:
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Thanks [~rubenql] for root causing this issue. This is exactly one of the
scenarios which CALCITE-2018 tries to fix. In current fix proposal, it clears
the parent RelNode's cost from the cache before propogating cost improvement to
the parent. Please try it out. It should fix this issue.
> VolcanoPlanner CannotPlanException: best rel is null even though there is an
> option with non-infinite cost
> ----------------------------------------------------------------------------------------------------------
>
> Key: CALCITE-3376
> URL: https://issues.apache.org/jira/browse/CALCITE-3376
> Project: Calcite
> Issue Type: Bug
> Affects Versions: 1.21.0
> Reporter: Ruben Q L
> Priority: Major
> Attachments: Diagram.png, Graphviz.png, logsTRACE.txt, stackTrace.txt
>
>
> The problem can be reproduced by adding this test to PlannerTest.java:
> {code:java}
> @Test public void testCannotPlanException() throws Exception {
> RelBuilder builder = RelBuilder.create(RelBuilderTest.config().build());
> RuleSet ruleSet =
> RuleSets.ofList(
> //EnumerableRules.ENUMERABLE_JOIN_RULE, // with this rule it
> works!
> JoinToCorrelateRule.INSTANCE,
> EnumerableRules.ENUMERABLE_CORRELATE_RULE,
> EnumerableRules.ENUMERABLE_PROJECT_RULE,
> EnumerableRules.ENUMERABLE_FILTER_RULE,
> EnumerableRules.ENUMERABLE_SORT_RULE,
> EnumerableRules.ENUMERABLE_UNION_RULE,
> EnumerableRules.ENUMERABLE_TABLE_SCAN_RULE);
> builder
> .scan("EMP")
> .scan("EMP")
> .union(true)
> .scan("EMP")
> .scan("EMP")
> .union(true)
> .join(
> JoinRelType.INNER,
> builder.equals(
> builder.field(2, 0, "DEPTNO"),
> builder.field(2, 1, "EMPNO")));
> RelNode relNode = builder.build();
> RelOptPlanner planner = relNode.getCluster().getPlanner();
> Program program = Programs.of(ruleSet);
> RelTraitSet toTraits = relNode.getTraitSet()
> .replace(EnumerableConvention.INSTANCE);
> RelNode output = program.run(planner, relNode, toTraits,
> ImmutableList.of(), ImmutableList.of());
> String outputStr = toString(output);
> }
> {code}
> Running this test causes the following exception (full stack trace attached):
> {code:java}
> org.apache.calcite.plan.RelOptPlanner$CannotPlanException: There are not
> enough rules to produce a node with desired properties:
> convention=ENUMERABLE, sort=[]. All the inputs have relevant nodes, however
> the cost is still infinite.
> Root: rel#13:Subset#2.ENUMERABLE.[]
> {code}
> The last part of the message (_All the inputs have relevant nodes, however
> the cost is still infinite_) seems relevant, because we can see that
> {{rel#13}}'s best is {{null}}, and it should be {{rel#21}} (which has a
> non-infinite cost):
> {code:java}
> rel#13:Subset#2.ENUMERABLE.[], best=null, importance=1.0
> rel#14:AbstractConverter.ENUMERABLE.[](input=RelSubset#12,
> convention=ENUMERABLE, sort=[]), rowcount=117.6, cumulative cost={inf}
> rel#21:EnumerableCorrelate.ENUMERABLE.[](left=RelSubset#19,
> right=RelSubset#20, correlation=$cor0, joinType=inner, requiredColumns={7}),
> rowcount=1.0, cumulative cost={1770.6000000000001 rows, 2466.0 cpu, 0.0 io}
> {code}
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