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https://issues.apache.org/jira/browse/HIVE-1035?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Navis resolved HIVE-1035.
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Resolution: Duplicate
Applied option-1 in HIVE-3550
> limit can be optimized if the limit is happening on the reducer
> ---------------------------------------------------------------
>
> Key: HIVE-1035
> URL: https://issues.apache.org/jira/browse/HIVE-1035
> Project: Hive
> Issue Type: Bug
> Components: Query Processor
> Reporter: Namit Jain
>
> A query like:
> select ... from A join B.. limit 10;
> where the limit is performed on the reducer can be further optimized.
> Currently, all the operators on the reduce side will be done, but the
> ExecReducer will un-necessarily deserialize all the rows.
> The following optimizations can be done:
> 1. Do nothing in reduce() in ExecReducer.
> 2. Modify map-reduce framework so that it does not even invoke the reduce()
> method in ExecReducer.
> 2. may require some work from hadoop - but we should minimally do 1.
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