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https://issues.apache.org/jira/browse/CASSANDRA-5544?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13667984#comment-13667984
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Alex Liu commented on CASSANDRA-5544:
-------------------------------------
Current implementation only matches one mapper to a split. Existing code
doesn't set InputSplitSize (which means we can't change it to a smaller number
unless we change the code at setLocation method to do it), so we need more than
64k rows to have more than one mapper per node.
For vnode we need to support a virtual split which combines multiple small
splits.
> Hadoop jobs assigns only one mapper in task
> --------------------------------------------
>
> Key: CASSANDRA-5544
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5544
> Project: Cassandra
> Issue Type: Bug
> Components: Hadoop
> Affects Versions: 1.2.1
> Environment: Red hat linux 5.4, Hadoop 1.0.3, pig 0.11.1
> Reporter: Shamim Ahmed
> Assignee: Alex Liu
> Attachments: Screen Shot 2013-05-26 at 4.49.48 PM.png
>
>
> We have got very strange beheviour of hadoop cluster after upgrading
> Cassandra from 1.1.5 to Cassandra 1.2.1. We have 5 nodes cluster of
> Cassandra, where three of them are hodoop slaves. Now when we are submitting
> job through Pig script, only one map assigns in task running on one of the
> hadoop slaves regardless of
> volume of data (already tried with more than million rows).
> Configure of pig as follows:
> export PIG_HOME=/oracle/pig-0.10.0
> export PIG_CONF_DIR=${HADOOP_HOME}/conf
> export PIG_INITIAL_ADDRESS=192.168.157.103
> export PIG_RPC_PORT=9160
> export PIG_PARTITIONER=org.apache.cassandra.dht.Murmur3Partitioner
> Also we have these following properties in hadoop:
> <property>
> <name>mapred.tasktracker.map.tasks.maximum</name>
> <value>10</value>
> </property>
> <property>
> <name>mapred.map.tasks</name>
> <value>4</value>
> </property>
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