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From "Kay Ousterhout (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (SPARK-6026) Eliminate the bypassMergeThreshold parameter and associated hash-ish shuffle within the Sort shuffle code
Date Thu, 26 Feb 2015 03:50:04 GMT

     [ https://issues.apache.org/jira/browse/SPARK-6026?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Kay Ousterhout updated SPARK-6026:
----------------------------------
    Description: 
The bypassMergeThreshold parameter (and associated use of a hash-ish shuffle when the number
of partitions is less than this) is basically a workaround for SparkSQL, because the fact
that the sort-based shuffle stores non-serialized objects is a deal-breaker for SparkSQL,
which re-uses objects.  Once the sort-based shuffle is changed to store serialized objects,
we should never be secretly doing hash-ish shuffle even when the user has specified to use
sort-based shuffle (because of its otherwise worse performance).

[~rxin][~adav], masters of shuffle, it would be helpful to get agreement from you on this
proposal (and also a sanity check that I've correctly characterized the issue).

  was:
The bypassMergeThreshold parameter (and associated use of a hash-ish shuffle when the number
of partitions is less than this) is basically a workaround for SparkSQL, because the fact
that the sort-based shuffle stores non-serialized objects is a deal-breaker for SparkSQL,
which re-uses objects.  Once the sort-based shuffle is changed to store serialized object,
we should never be secretly doing hash-ish shuffle even when the user has specified to use
sort-based shuffle (because of its otherwise worse performance).

[~rxin][~adav], masters of shuffle, it would be helpful to get agreement from you on this
proposal (and also a sanity check that I've correctly characterized the issue).


> Eliminate the bypassMergeThreshold parameter and associated hash-ish shuffle within the
Sort shuffle code
> ---------------------------------------------------------------------------------------------------------
>
>                 Key: SPARK-6026
>                 URL: https://issues.apache.org/jira/browse/SPARK-6026
>             Project: Spark
>          Issue Type: Bug
>    Affects Versions: 1.3.0
>            Reporter: Kay Ousterhout
>
> The bypassMergeThreshold parameter (and associated use of a hash-ish shuffle when the
number of partitions is less than this) is basically a workaround for SparkSQL, because the
fact that the sort-based shuffle stores non-serialized objects is a deal-breaker for SparkSQL,
which re-uses objects.  Once the sort-based shuffle is changed to store serialized objects,
we should never be secretly doing hash-ish shuffle even when the user has specified to use
sort-based shuffle (because of its otherwise worse performance).
> [~rxin][~adav], masters of shuffle, it would be helpful to get agreement from you on
this proposal (and also a sanity check that I've correctly characterized the issue).



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