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https://issues.apache.org/jira/browse/CALCITE-2018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16952268#comment-16952268
 ] 

Xiening Dai commented on CALCITE-2018:
--------------------------------------

I can disable the validation in test. But I would also love to know what are 
the extra things that are computed and affect the behavior. As I examine the 
code path, the only stateful object updated in the validation pass is the 
RelMetadataQuery.map. But since the RelMetadataQuery object used in validation 
is a complete new object, that would not affect planner's behavior IMO.

The change with RelMetadataQuery is to make sure we have one single 
RelMetadataQuery instance during the rule firing, so we can avoid the overhead 
of instantiation of RelMetadataQuery and reuse the RelNode cost cache 
(RelMetadataQuery.map). For this fix, I think the bigger change is to make sure 
we clean RelNode cost cache entries when best rel is updated. In order to 
remove a single cache entry, the cache map structure is also updated to include 
RelNode as a key.

Regarding the minor point, this part was authored by [~volodymyr] But I can 
made an update to swap the two arguments. 

Thanks.

> 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: Vova Vysotskyi
>            Assignee: Danny Chen
>            Priority: Critical
>              Labels: pull-request-available
>          Time Spent: 2h 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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