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From "Tejas Patil (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-12394) Support writing out pre-hash-partitioned data and exploit that in join optimizations to avoid shuffle (i.e. bucketing in Hive)
Date Fri, 26 Aug 2016 03:47:20 GMT

    [ https://issues.apache.org/jira/browse/SPARK-12394?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15438423#comment-15438423
] 

Tejas Patil commented on SPARK-12394:
-------------------------------------

[~alex.n.james@gmail.com] [~kotime42@gmail.com] : The doc lists two things for future in the
end. I am working on the last one : https://issues.apache.org/jira/browse/SPARK-15453. I am
not sure if the `Filter on sorted data` one is already being worked on but I can work on that
as well (just created a jira for that : https://issues.apache.org/jira/browse/SPARK-17254)

> Support writing out pre-hash-partitioned data and exploit that in join optimizations
to avoid shuffle (i.e. bucketing in Hive)
> ------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: SPARK-12394
>                 URL: https://issues.apache.org/jira/browse/SPARK-12394
>             Project: Spark
>          Issue Type: New Feature
>          Components: SQL
>            Reporter: Reynold Xin
>            Assignee: Nong Li
>             Fix For: 2.0.0
>
>         Attachments: BucketedTables.pdf
>
>
> In many cases users know ahead of time the columns that they will be joining or aggregating
on.  Ideally they should be able to leverage this information and pre-shuffle the data so
that subsequent queries do not require a shuffle.  Hive supports this functionality by allowing
the user to define buckets, which are hash partitioning of the data based on some key.
>  - Allow the user to specify a set of columns when caching or writing out data
>  - Allow the user to specify some parallelism
>  - Shuffle the data when writing / caching such that its distributed by these columns
>  - When planning/executing  a query, use this distribution to avoid another shuffle when
reading, assuming the join or aggregation is compatible with the columns specified
>  - Should work with existing save modes: append, overwrite, etc
>  - Should work at least with all Hadoops FS data sources
>  - Should work with any data source when caching



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