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https://issues.apache.org/jira/browse/CALCITE-2018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16818872#comment-16818872
 ] 

Volodymyr Vysotskyi commented on CALCITE-2018:
----------------------------------------------

[~danny0405], thanks for moving this issue forward. This issue partially solves 
the problem with propagating best cost including the fixes for preserving only 
actual `RelMetadataQuery`.

But it is blocked by a more serious problem - CALCITE-2166 where was shown that 
the cumulative cost of best rel node actually is not always the best cost, the 
problem there with the way how the best cost is calculated.

PS. I have rebased my PR onto the master and resolved all the conflicts.
Also, I don't mind fixing this Jira either with the fix I proposed or any 
alternative fix, the main thing is to resolve not fewer problematic cases 
compared to the original PR.

> Queries failed with AssertionError: rel has lower cost than best cost of 
> subset
> -------------------------------------------------------------------------------
>
>                 Key: CALCITE-2018
>                 URL: https://issues.apache.org/jira/browse/CALCITE-2018
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.13.0
>            Reporter: Volodymyr Vysotskyi
>            Assignee: Danny Chan
>            Priority: Critical
>              Labels: pull-request-available
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
> *Problem description*
> When rootLogger level is DEBUG, unit tests 
> * MaterializationTest.testMaterializationSubstitution2
> * MaterializationTest.testJoinMaterializationUKFK8
> * MaterializationTest.testJoinMaterializationUKFK6
> * JdbcTest.testWhereNot
> unit tests are failed with error AssertionError: rel has lower cost than best 
> cost of subset.
> Full stack trace for test 
> {{MaterializationTest.testMaterializationSubstitution2}}:
> {noformat}
> java.lang.AssertionError: rel 
> [rel#245:EnumerableUnion.ENUMERABLE.[](input#0=rel#246:Subset#5.ENUMERABLE.[],input#1=rel#239:Subset#6.ENUMERABLE.[0],all=true)]
>  has lower cost {14.0 rows, 19.0 cpu, 0.0 io} than best cost {15.0 rows, 20.0 
> cpu, 0.0 io} of subset [rel#243:Subset#7.ENUMERABLE.[]]
>       at 
> org.apache.calcite.plan.volcano.VolcanoPlanner.validate(VolcanoPlanner.java:906)
>       at 
> org.apache.calcite.plan.volcano.VolcanoPlanner.register(VolcanoPlanner.java:866)
>       at 
> org.apache.calcite.plan.volcano.VolcanoPlanner.ensureRegistered(VolcanoPlanner.java:883)
>       at 
> org.apache.calcite.plan.volcano.VolcanoPlanner.ensureRegistered(VolcanoPlanner.java:101)
>       at 
> org.apache.calcite.rel.AbstractRelNode.onRegister(AbstractRelNode.java:336)
>       at 
> org.apache.calcite.plan.volcano.VolcanoPlanner.registerImpl(VolcanoPlanner.java:1495)
>       at 
> org.apache.calcite.plan.volcano.VolcanoPlanner.register(VolcanoPlanner.java:863)
>       at 
> org.apache.calcite.plan.volcano.VolcanoPlanner.ensureRegistered(VolcanoPlanner.java:883)
>       at 
> org.apache.calcite.plan.volcano.VolcanoPlanner.ensureRegistered(VolcanoPlanner.java:1766)
>       at 
> org.apache.calcite.plan.volcano.VolcanoRuleCall.transformTo(VolcanoRuleCall.java:135)
>       at 
> org.apache.calcite.plan.RelOptRuleCall.transformTo(RelOptRuleCall.java:234)
>       at 
> org.apache.calcite.rel.rules.FilterProjectTransposeRule.onMatch(FilterProjectTransposeRule.java:143)
>       at 
> org.apache.calcite.plan.volcano.VolcanoRuleCall.onMatch(VolcanoRuleCall.java:212)
>       at 
> org.apache.calcite.plan.volcano.VolcanoPlanner.findBestExp(VolcanoPlanner.java:650)
>       at org.apache.calcite.tools.Programs$5.run(Programs.java:326)
>       at 
> org.apache.calcite.tools.Programs$SequenceProgram.run(Programs.java:387)
>       at org.apache.calcite.prepare.Prepare.optimize(Prepare.java:187)
>       at org.apache.calcite.prepare.Prepare.prepareSql(Prepare.java:318)
>       at org.apache.calcite.prepare.Prepare.prepareSql(Prepare.java:229)
>       at 
> org.apache.calcite.prepare.CalcitePrepareImpl.prepare2_(CalcitePrepareImpl.java:786)
>       at 
> org.apache.calcite.prepare.CalcitePrepareImpl.prepare_(CalcitePrepareImpl.java:640)
>       at 
> org.apache.calcite.prepare.CalcitePrepareImpl.prepareSql(CalcitePrepareImpl.java:610)
>       at org.apache.calcite.schema.Schemas.prepare(Schemas.java:346)
>       at 
> org.apache.calcite.materialize.MaterializationService$DefaultTableFactory.createTable(MaterializationService.java:374)
>       at 
> org.apache.calcite.materialize.MaterializationService.defineMaterialization(MaterializationService.java:137)
>       at 
> org.apache.calcite.materialize.MaterializationService.defineMaterialization(MaterializationService.java:99)
>       at 
> org.apache.calcite.schema.impl.MaterializedViewTable$MaterializedViewTableMacro.<init>(MaterializedViewTable.java:110)
>       at 
> org.apache.calcite.schema.impl.MaterializedViewTable$MaterializedViewTableMacro.<init>(MaterializedViewTable.java:100)
>       at 
> org.apache.calcite.schema.impl.MaterializedViewTable.create(MaterializedViewTable.java:81)
>       at org.apache.calcite.model.ModelHandler.visit(ModelHandler.java:364)
>       at 
> org.apache.calcite.model.JsonMaterialization.accept(JsonMaterialization.java:42)
>       at org.apache.calcite.model.JsonSchema.visitChildren(JsonSchema.java:98)
>       at 
> org.apache.calcite.model.JsonMapSchema.visitChildren(JsonMapSchema.java:48)
>       at 
> org.apache.calcite.model.ModelHandler.populateSchema(ModelHandler.java:257)
>       at org.apache.calcite.model.ModelHandler.visit(ModelHandler.java:273)
>       at 
> org.apache.calcite.model.JsonCustomSchema.accept(JsonCustomSchema.java:45)
>       at org.apache.calcite.model.ModelHandler.visit(ModelHandler.java:196)
>       at org.apache.calcite.model.ModelHandler.<init>(ModelHandler.java:88)
>       at org.apache.calcite.jdbc.Driver$1.onConnectionInit(Driver.java:104)
>       at 
> org.apache.calcite.avatica.UnregisteredDriver.connect(UnregisteredDriver.java:139)
>       at java.sql.DriverManager.getConnection(DriverManager.java:571)
>       at java.sql.DriverManager.getConnection(DriverManager.java:187)
>       at 
> org.apache.calcite.test.CalciteAssert$MapConnectionFactory.createConnection(CalciteAssert.java:1227)
>       at 
> org.apache.calcite.test.CalciteAssert$AssertQuery.createConnection(CalciteAssert.java:1266)
>       at 
> org.apache.calcite.test.CalciteAssert$AssertQuery.returns(CalciteAssert.java:1337)
>       at 
> org.apache.calcite.test.CalciteAssert$AssertQuery.returns(CalciteAssert.java:1320)
>       at 
> org.apache.calcite.test.CalciteAssert$AssertQuery.sameResultWithMaterializationsDisabled(CalciteAssert.java:1548)
>       at 
> org.apache.calcite.test.MaterializationTest.testMaterializationSubstitution2(MaterializationTest.java:2062)
>       at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>       at 
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
>       at 
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>       at java.lang.reflect.Method.invoke(Method.java:606)
>       at 
> org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
>       at 
> org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
>       at 
> org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
>       at 
> org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
>       at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
>       at 
> org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
>       at 
> org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
>       at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
>       at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
>       at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
>       at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
>       at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
>       at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
>       at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
>       at 
> com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
>       at 
> com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
>       at 
> com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
>       at 
> com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
> {noformat}
> *Possible root cause*
> JaninoRelMetadataProvider caches metadata queries of {{RelSubset}} even when 
> {{RelSubset.best}} value is not set. 
> Actually not all RelNodes in {{RelSubset.set.rels}} have the same row count 
> for some queries.
> When {{RelMetadataQuery.getRowCount(RelNode rel)}} method is called with 
> {{RelSubset}} instance without best value, row count of {{RelSubset.set.rel}} 
> is cached. 
> After assigning best relNode, the {{RelMetadataQuery.getRowCount(RelNode 
> rel)}} method returns old cached value if {{RelMetadataQuery}} instance still 
> the same. 
> This error appears when row count for best relNode is different from set.rel 
> relNode.
> In the test {{MaterializationTest.testMaterializationSubstitution2}} row 
> count of {{rel#237:LogicalFilter}} was cached and returned its value when 
> relSubset had best {{rel#347:EnumerableFilter}}.



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