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From "Zheng Shao (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-224) implement lfu based flushing policy for map side aggregates
Date Fri, 05 Mar 2010 05:49:27 GMT

    [ https://issues.apache.org/jira/browse/HIVE-224?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12841714#action_12841714
] 

Zheng Shao commented on HIVE-224:
---------------------------------

Hi James, currently we don't have the bandwidth to do this, but I guess it won't be too hard
- we just need to use http://java.sun.com/j2se/1.4.2/docs/api/java/util/LinkedHashMap.html
(search for LRU).
Are you interested in joining force on this?


> implement lfu based flushing policy for map side aggregates
> -----------------------------------------------------------
>
>                 Key: HIVE-224
>                 URL: https://issues.apache.org/jira/browse/HIVE-224
>             Project: Hadoop Hive
>          Issue Type: Improvement
>            Reporter: Joydeep Sen Sarma
>
> currently we flush some random set of rows when the map side hash table approaches memory
limits.
> we have discussed a strategy of flushing hash table entries that have the been seen the
least number of times (effectively LFU flushing strategy). This will be very effective at
reducing the amount of data sent from map to reduce step - as well as reduce the chances for
any skews.

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