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https://issues.apache.org/jira/browse/HIVE-2144?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ning Zhang reassigned HIVE-2144:
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Assignee: Tomasz Nykiel (was: Ning Zhang)
> reduce workload generated by JDBCStatsPublisher
> -----------------------------------------------
>
> Key: HIVE-2144
> URL: https://issues.apache.org/jira/browse/HIVE-2144
> Project: Hive
> Issue Type: Improvement
> Reporter: Ning Zhang
> Assignee: Tomasz Nykiel
>
> In JDBCStatsPublisher, we first try a SELECT query to see if the specific ID
> was inserted by another task (mostly likely a speculative or previously
> failed task). Depending on if the ID is there, an INSERT or UPDATE query was
> issues. So there are basically 2x of queries per row inserted into the
> intermediate stats table. This workload could be reduced to 1/2 if we insert
> it anyway (it is very rare that IDs are duplicated) and use a different SQL
> query in the aggregation phase to dedup the ID (e.g., using group-by and
> max()). The benefits are that even though the aggregation query is more
> expensive, it is only run once per query.
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