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https://issues.apache.org/jira/browse/CALCITE-2018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16293885#comment-16293885
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Volodymyr Vysotskyi commented on CALCITE-2018:
----------------------------------------------
I have just faced up with the more serious consequence of this issue: in the
query, where 5 tables are joining, {{JoinToMultiJoinRule}} could not be applied
correctly, since instead of one of the joins, project with that join was
specified. This project actually also had greater cost in its subset than join
rel node, but because of this bug, project rel node was chosen as the best.
In fact, RelNode is not immutable, especially when it has RelSubset as an
input. We could not cache RelNode metadata blindly expecting that it does not
change. It's a matter of time before more serious consequences would be
discovered.
> 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: Julian Hyde
> Fix For: 1.16.0
>
>
> *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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