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https://issues.apache.org/jira/browse/CALCITE-2018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16293963#comment-16293963
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Julian Hyde commented on CALCITE-2018:
--------------------------------------
I agree that this is a serious problem.
It's not easy to solve because, as you say, the statistics and RelNode graph
are constantly changing. The current strategy is to use clock ticks (one tick
each time a planner rule fires and produces a result), to flush the cache on
the clock tick, and assume that it is constant for the duration of the tick. I
believe that if we tried to explicitly propagate improvements up through the
graph we would hit performance problems, correctness problems, and cycles.
Of course there is some mutable state in the RelNode graph. (Otherwise we'd
have to copy virtually the entire graph each time a rule fired.) But that
doesn't mean that adding more mutable state is the solution.
> 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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