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https://issues.apache.org/jira/browse/HIVE-27375?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17731930#comment-17731930
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Denys Kuzmenko commented on HIVE-27375:
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Merged to master.
Thanks for the contribution [~seonggon] and [~akshatm], [~rkirtir] for the
review!
> SharedWorkOptimizer assigns a common cache key to MapJoin operators that
> should not share MapJoin tables
> --------------------------------------------------------------------------------------------------------
>
> Key: HIVE-27375
> URL: https://issues.apache.org/jira/browse/HIVE-27375
> Project: Hive
> Issue Type: Bug
> Reporter: Sungwoo Park
> Assignee: Seonggon Namgung
> Priority: Major
> Labels: pull-request-available
>
> When hive.optimize.shared.work.mapjoin.cache.reuse is set to true,
> SharedWorkOptimizer sometimes assigns a common cache key to MapJoin operators
> that should not share MapJoin tables. This bug occurs only for MapJoin
> operators with 3 or more parent operators.
> Example:
> MAPJOIN[575] (RS_83, GBY_66, RS_85)
> MAPJOIN[585] (RS_212, RS_213, GBY_210)
> In this example, both MAPJOIN[575] and MAPJOIN[585] have three parent
> operators. The current implementation assigns a common cache key to
> MAPJOIN[575] and MAPJOIN[585] because RS_83 are RS_212 are equivalent.
> However, MAPJOIN[575] uses GBY_66 for its big table whereas MAPJOIN[585] uses
> GBY_210 for its big table. As a result, the MapJoin table loaded by one
> operator cannot be used by the other.
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