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https://issues.apache.org/jira/browse/HIVE-1404?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Carl Steinbach updated HIVE-1404:
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Affects Version/s: 0.5.0
Component/s: Query Processor
UDF
> Allow UDAFs to turn off map-side aggregation
> --------------------------------------------
>
> Key: HIVE-1404
> URL: https://issues.apache.org/jira/browse/HIVE-1404
> Project: Hadoop Hive
> Issue Type: New Feature
> Components: Query Processor, UDF
> Affects Versions: 0.5.0
> Reporter: Jonathan Chang
> Priority: Minor
>
> Some UDAFs such as COLLECT will not work with map-side aggregation (because
> each mapper must hold all of its contents in memory). To use such a
> function at the moment, one has to remember to set hive.map.aggr. This has
> two problems:
> 1.) The user has to remember to set this flag or else bad things will happen.
> 2.) The flag applies to the entire query plan rather than just the block
> containing the COLLECT statement.
> It would be good to have a bit in the UDAF which would tell the compiler to
> turn off map-side aggregation for just the block containing the UDAF.
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