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https://issues.apache.org/jira/browse/FLINK-20899?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Flink Jira Bot updated FLINK-20899:
-----------------------------------
    Labels: pull-request-available stale-assigned  (was: pull-request-available)

> encounter ClassCastException when calculating cost in HepPlanner
> ----------------------------------------------------------------
>
>                 Key: FLINK-20899
>                 URL: https://issues.apache.org/jira/browse/FLINK-20899
>             Project: Flink
>          Issue Type: Bug
>          Components: Table SQL / Planner
>            Reporter: godfrey he
>            Assignee: godfrey he
>            Priority: Major
>              Labels: pull-request-available, stale-assigned
>
> After TREACE level is enabled for Logger, we will encounter 
> ClassCastException when executing the following query:
> {code:sql}
> SELECT COUNT(*) FROM MyTable
> {code}
> the exception detail is:
> {code:java}
> java.lang.ClassCastException: org.apache.calcite.plan.RelOptCostImpl$Factory 
> cannot be cast to org.apache.flink.table.planner.plan.cost.FlinkCostFactory
>       at 
> org.apache.flink.table.planner.plan.nodes.physical.common.CommonPhysicalExchange.computeSelfCost(CommonPhysicalExchange.scala:53)
>       at 
> org.apache.flink.table.planner.plan.metadata.FlinkRelMdNonCumulativeCost.getNonCumulativeCost(FlinkRelMdNonCumulativeCost.scala:41)
>       at 
> GeneratedMetadataHandler_NonCumulativeCost.getNonCumulativeCost_$(Unknown 
> Source)
>       at 
> GeneratedMetadataHandler_NonCumulativeCost.getNonCumulativeCost(Unknown 
> Source)
>       at 
> org.apache.calcite.rel.metadata.RelMetadataQuery.getNonCumulativeCost(RelMetadataQuery.java:288)
>       at 
> org.apache.flink.table.planner.plan.metadata.FlinkRelMdCumulativeCost.getCumulativeCost(FlinkRelMdCumulativeCost.scala:38)
>       at GeneratedMetadataHandler_CumulativeCost.getCumulativeCost_$(Unknown 
> Source)
>       at GeneratedMetadataHandler_CumulativeCost.getCumulativeCost(Unknown 
> Source)
>       at GeneratedMetadataHandler_CumulativeCost.getCumulativeCost_$(Unknown 
> Source)
>       at GeneratedMetadataHandler_CumulativeCost.getCumulativeCost(Unknown 
> Source)
>       at 
> org.apache.calcite.rel.metadata.RelMetadataQuery.getCumulativeCost(RelMetadataQuery.java:269)
>       at 
> org.apache.flink.table.planner.plan.metadata.FlinkRelMdCumulativeCost$$anonfun$getCumulativeCost$1.apply(FlinkRelMdCumulativeCost.scala:41)
>       at 
> org.apache.flink.table.planner.plan.metadata.FlinkRelMdCumulativeCost$$anonfun$getCumulativeCost$1.apply(FlinkRelMdCumulativeCost.scala:40)
>       at 
> scala.collection.TraversableOnce$$anonfun$foldLeft$1.apply(TraversableOnce.scala:157)
>       at 
> scala.collection.TraversableOnce$$anonfun$foldLeft$1.apply(TraversableOnce.scala:157)
>       at scala.collection.Iterator$class.foreach(Iterator.scala:891)
>       at scala.collection.AbstractIterator.foreach(Iterator.scala:1334)
>       at scala.collection.IterableLike$class.foreach(IterableLike.scala:72)
>       at scala.collection.AbstractIterable.foreach(Iterable.scala:54)
>       at 
> scala.collection.TraversableOnce$class.foldLeft(TraversableOnce.scala:157)
>       at scala.collection.AbstractTraversable.foldLeft(Traversable.scala:104)
>       at 
> org.apache.flink.table.planner.plan.metadata.FlinkRelMdCumulativeCost.getCumulativeCost(FlinkRelMdCumulativeCost.scala:39)
>       at GeneratedMetadataHandler_CumulativeCost.getCumulativeCost_$(Unknown 
> Source)
>       at GeneratedMetadataHandler_CumulativeCost.getCumulativeCost(Unknown 
> Source)
>       at 
> org.apache.calcite.rel.metadata.RelMetadataQuery.getCumulativeCost(RelMetadataQuery.java:269)
>       at 
> org.apache.calcite.plan.AbstractRelOptPlanner.getCost(AbstractRelOptPlanner.java:247)
>       at 
> org.apache.calcite.plan.hep.HepPlanner.dumpGraph(HepPlanner.java:1023)
>       at org.apache.calcite.plan.hep.HepPlanner.setRoot(HepPlanner.java:159)
>       at 
> org.apache.flink.table.planner.plan.optimize.program.FlinkHepProgram.optimize(FlinkHepProgram.scala:60)
> {code}
> The reason is the HepPlanner will calculate the cost of the optimized plan 
> when TRACE is enabled, while the cost factory in hep planner is 
> {{RelOptCostImpl.Factory}}, not the sub-class of FlinkCostFactory.
> The solution is we should create HepPlanner with the cost factory in the 
> RelOptCluster.



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