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https://issues.apache.org/jira/browse/HIVE-4105?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vinod Kumar Vavilapalli updated HIVE-4105:
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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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