[CALCITE-2773] Prune of empty values causes assertion error "rel cost is lower than best cost"

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.18.0
• Component/s: core
• Assignee: Unassigned
• Reporter: Vladimir Sitnikov
• Created: 07/Jan/19 18:53
• Updated: 22/Feb/19 01:21

Description

Prune of empty values causes assertion error "rel cost is lower than best cost".

values(1)
 union all values(2)
 union all select * from (values(3)) where false

it is parsed as

LogicalUnion(all=[true])
  LogicalUnion(all=[true])
    LogicalValues(tuples=[[{ 1 }]])
    LogicalProject(EXPR$0=[$0])
      LogicalFilter(condition=[false])
        LogicalValues(tuples=[[{ 3 }]])
  LogicalValues(tuples=[[{ 2 }]])

Then it fails as follows:

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)

Issue Links

• is related to: CALCITE-2018 Queries failed with AssertionError: rel has lower cost than best cost of subset