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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Issue Comment Edited] (CASSANDRA-1473) Implement a Cassandra aware Hadoop mapreduce.Partitioner
Date Thu, 11 Aug 2011 13:55:27 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1473?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13083117#comment-13083117
] 

Jonathan Ellis edited comment on CASSANDRA-1473 at 8/11/11 1:54 PM:
--------------------------------------------------------------------

{noformat}
/** Get the partition number for a given key (hence record) given the total number of partitions
*/
getPartition(KEY key, VALUE value, int numPartitions)
{noformat}

I don't think we can do this, without knowing the total number of keys as well. :(

      was (Author: jbellis):
    {noformat}
/** Get the partition number for a given key (hence record) given the total number of partitions
*/
getPartition(KEY key, VALUE value, int numPartitions)
*/
{noformat}

I don't think we can do this, without knowing the total number of keys as well. :(
  
> Implement a Cassandra aware Hadoop mapreduce.Partitioner
> --------------------------------------------------------
>
>                 Key: CASSANDRA-1473
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1473
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Hadoop
>            Reporter: Stu Hood
>            Assignee: Patricio Echague
>             Fix For: 1.0
>
>
> When using a IPartitioner that does not sort data in byte order (RandomPartitioner for
example) with Cassandra's Hadoop integration, Hadoop is unaware of the output order of the
data.
> We can make Hadoop aware of the proper order of the output data by implementing Hadoop's
mapreduce.Partitioner interface: then Hadoop will handle sorting all of the data according
to Cassandra's IPartitioner, and the writing clients will be able to connect to smaller numbers
of Cassandra nodes.

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