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https://issues.apache.org/jira/browse/CALCITE-2773?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16736224#comment-16736224
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Vladimir Sitnikov commented on CALCITE-2773:
--------------------------------------------
[~julianhyde], thanks.
I've cherry-picked PR#552, and it does resolve the issue. However I haven't
reviewed it.
> Prune of empty values causes assertion error "rel cost is lower than best
> cost"
> -------------------------------------------------------------------------------
>
> Key: CALCITE-2773
> URL: https://issues.apache.org/jira/browse/CALCITE-2773
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.18.0
> Reporter: Vladimir Sitnikov
> Assignee: Julian Hyde
> Priority: Major
>
> Prune of empty values causes assertion error "rel cost is lower than best
> cost".
> {code:sql}
> values(1)
> union all values(2)
> union all select * from (values(3)) where false{code}
> it is parsed as
> {noformat}
> LogicalUnion(all=[true])
> LogicalUnion(all=[true])
> LogicalValues(tuples=[[{ 1 }]])
> LogicalProject(EXPR$0=[$0])
> LogicalFilter(condition=[false])
> LogicalValues(tuples=[[{ 3 }]])
> LogicalValues(tuples=[[{ 2 }]]){noformat}
> Then it fails as follows:
> {noformat}
> java.lang.AssertionError: rel
> [rel#69:EnumerableUnion.ENUMERABLE.[](input#0=RelSubset#78,input#1=RelSubset#71,all=true)]
> has lower cost {4.0 rows, 4.0 cpu, 0.0 io} than best cost {5.0 rows, 5.0
> cpu, 0.0 io} of subset [rel#67:Subset#6.ENUMERABLE.[]]
> at org.apache.calcite.util.Litmus$1.fail(Litmus.java:31)
> at
> org.apache.calcite.plan.volcano.VolcanoPlanner.isValid(VolcanoPlanner.java:896)
> at
> org.apache.calcite.plan.volcano.VolcanoPlanner.register(VolcanoPlanner.java:859)
> at
> org.apache.calcite.plan.volcano.VolcanoPlanner.ensureRegistered(VolcanoPlanner.java:876)
> at
> org.apache.calcite.plan.volcano.VolcanoPlanner.ensureRegistered(VolcanoPlanner.java:1747)
> at
> org.apache.calcite.plan.volcano.VolcanoRuleCall.transformTo(VolcanoRuleCall.java:136)
> at
> org.apache.calcite.plan.RelOptRuleCall.transformTo(RelOptRuleCall.java:236)
> at
> org.apache.calcite.rel.convert.ConverterRule.onMatch(ConverterRule.java:141)
> at
> org.apache.calcite.plan.volcano.VolcanoRuleCall.onMatch(VolcanoRuleCall.java:213)
> at
> org.apache.calcite.plan.volcano.VolcanoPlanner.findBestExp(VolcanoPlanner.java:641)
> at
> org.apache.calcite.tools.Programs$RuleSetProgram.run(Programs.java:339)
> at
> org.apache.calcite.prepare.PlannerImpl.transform(PlannerImpl.java:349)
> at
> org.apache.calcite.tools.PlannerTest.checkUnionPruning(PlannerTest.java:465)
> at
> org.apache.calcite.tools.PlannerTest.emptyUnions32(PlannerTest.java:436){noformat}
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