[jira] [Assigned] (HIVE-27375) SharedWorkOptimizer assigns a common cache key to MapJoin operators that should not share MapJoin tables

["Sungwoo Park (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-27375?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sungwoo Park reassigned HIVE-27375:
-----------------------------------

    Assignee: Seonggon Namgung

> 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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