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https://issues.apache.org/jira/browse/HIVE-4838?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13707181#comment-13707181
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Brock Noland commented on HIVE-4838:
------------------------------------
Hi,
Correct there is. It's related to the snippet of code I posted earlier.
Basically the equals implementation of MapJoinDoubleKey (and MapJoinObjectKey)
is incorrect resulting in different results for the following query depending
on how it executed (map-side vs reduce-side):
{noformat}
SELECT /*+ MAPJOIN(a) */ * FROM smb_input1 a JOIN smb_input1 b ON a.key <=>
b.key AND a.value <=> b.value ORDER BY a.key, a.value, b.key, b.value;
{noformat}
Brock
> 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
>
>
> 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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