[jira] [Commented] (FLINK-2871) Add OuterJoin strategy with HashTable on outer side

["Chengxiang Li (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-2871?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15061322#comment-15061322 ] 

Chengxiang Li commented on FLINK-2871:
--------------------------------------

I would like to contribute on this. There are 4 reserved bytes left in bucket header of {{MutableHashTable}}, as there are only 9 elements in each bucket, we could use 2 bytes to build a BitSet to mark whether elements in each bucket has been probed during probe phase, and return the elements which has not been probed at the end.

> Add OuterJoin strategy with HashTable on outer side
> ---------------------------------------------------
>
>                 Key: FLINK-2871
>                 URL: https://issues.apache.org/jira/browse/FLINK-2871
>             Project: Flink
>          Issue Type: New Feature
>          Components: Local Runtime, Optimizer
>    Affects Versions: 0.10.0
>            Reporter: Fabian Hueske
>            Priority: Minor
>
> Outer joins are currently supported with two local execution strategies:
> - sort-merge join
> - hash join where the hash table is built on the inner side. Hence, this strategy is only supported for left and right outer joins.
> In order to support hash-tables on the outer side, we need a special hash table implementation that gives access to all records which have not been accessed during the probe phase.



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