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https://issues.apache.org/jira/browse/HIVE-2144?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13038932#comment-13038932
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Hudson commented on HIVE-2144:
------------------------------
Integrated in Hive-trunk-h0.21 #748 (See
[https://builds.apache.org/hudson/job/Hive-trunk-h0.21/748/])
HIVE-2144. reduce workload generated by JDBCStatsPublisher (Tomasz Nykiel
via Ning Zhang)
nzhang : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1127229
Files :
* /hive/trunk/ql/src/test/org/apache/hadoop/hive/ql/exec/TestStatsPublisher.java
*
/hive/trunk/ql/src/java/org/apache/hadoop/hive/ql/stats/jdbc/JDBCStatsPublisher.java
> 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
> Fix For: 0.8.0
>
> Attachments: HIVE-2144.1.patch, HIVE-2144.2.patch, HIVE-2144.patch
>
>
> 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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