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From "Vinod Kumar Vavilapalli (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-4105) Hive MapJoinOperator unnecessarily deserializes values for all join-keys
Date Fri, 01 Mar 2013 23:33:13 GMT

     [ https://issues.apache.org/jira/browse/HIVE-4105?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vinod Kumar Vavilapalli updated HIVE-4105:
------------------------------------------

    Attachment: HIVE-4105-20130301.txt

Here's a patch to avoid value de-serialization where not needed in case of inner join.

In my microbenchmark, where I was map-joining a big table, with a small table, this brought
the task execution time down from 15seconds to 10seconds on about 3 million records on the
big table, the second table being very small and the output is small too. Note that you won't
see this much of an improvement for non-selective inner joins.

If folks are interested, I'll try productionizing the benchmark.
                
> Hive MapJoinOperator unnecessarily deserializes values for all join-keys
> ------------------------------------------------------------------------
>
>                 Key: HIVE-4105
>                 URL: https://issues.apache.org/jira/browse/HIVE-4105
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Vinod Kumar Vavilapalli
>         Attachments: HIVE-4105-20130301.txt
>
>
> We can avoid this for inner-joins. Hive does an explicit value de-serialization up front
so even for those rows which won't emit output. In these cases, we can do just with key de-serialization.

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