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https://issues.apache.org/jira/browse/HIVE-4838?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13732571#comment-13732571
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Brock Noland commented on HIVE-4838:
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What I was saying is the the local task JVM could be of different size than the
mapred.child.java.opts on the server. I haven't heard of people hitting this
much so it must not be too much of an issue. Good to know the ORC stuff is only
used on write so it won't be an issue.
I am fine with removing the memory handling and using OOM. I think that I will
allocate a buffer of say 1MB and then when the OOM is hit free that buffer so
we can cleanly exit and log.
> Refactor MapJoin HashMap code to improve testability and readability
> --------------------------------------------------------------------
>
> Key: HIVE-4838
> URL: https://issues.apache.org/jira/browse/HIVE-4838
> Project: Hive
> Issue Type: Bug
> Reporter: Brock Noland
> Assignee: Brock Noland
> Attachments: HIVE-4838.patch, HIVE-4838.patch, HIVE-4838.patch,
> HIVE-4838.patch, HIVE-4838.patch
>
>
> MapJoin is an essential component for high performance joins in Hive and the
> current code has done great service for many years. However, the code is
> showing it's age and currently suffers from the following issues:
> * Uses static state via the MapJoinMetaData class to pass serialization
> metadata to the Key, Row classes.
> * The api of a logical "Table Container" is not defined and therefore it's
> unclear what apis HashMapWrapper
> needs to publicize. Additionally HashMapWrapper has many used public methods.
> * HashMapWrapper contains logic to serialize, test memory bounds, and
> implement the table container. Ideally these logical units could be seperated
> * HashTableSinkObjectCtx has unused fields and unused methods
> * CommonJoinOperator and children use ArrayList on left hand side when only
> List is required
> * There are unused classes MRU, DCLLItemm and classes which duplicate
> functionality MapJoinSingleKey and MapJoinDoubleKeys
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