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https://issues.apache.org/jira/browse/CASSANDRA-4259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13395970#comment-13395970
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Jonathan Ellis commented on CASSANDRA-4259:
-------------------------------------------
To clarify: this was a regression introduced in 1.1.0, it should not affect
1.0.x.
> Bug in SSTableReader.getSampleIndexesForRanges(...) causes uneven InputSplits
> generation for Hadoop mappers
> -----------------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-4259
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4259
> Project: Cassandra
> Issue Type: Bug
> Components: Hadoop
> Affects Versions: 1.1.0
> Environment: Small cassandra cluster with 2 nodes. Version 1.1.0.
> Tokens: 0, 85070591730234615865843651857942052864
> Hadoop 1.0.1 and Pig 0.10.0.
> Reporter: Bartłomiej Romański
> Assignee: Bartłomiej Romański
> Fix For: 1.1.1
>
>
> Running a simple mapreduce job on cassandra column family results in creating
> multiple small mappers for one half of the ring and one big mapper for the
> other half. Upper part (85... - 0) is cut into smaller slices. Lower part (0
> - 85...) generates one big input slice. One mapper processing half of the
> ring causes huge inefficiency. Also the progress meter for this mapper is
> incorrect - it goes to 100% in a couple of seconds, than stays at 100% for an
> hour or two.
> I've investigated the problem a bit. I think it is related to incorrect
> output of 'nodetool rangekeysample'. On the node resposible for part (0 -
> 85...) the output is empty! On the other node it works fine.
> I think the bug is in SSTableReader.getSampleIndexesForRanges(...). These two
> lines:
> RowPosition leftPosition = range.left.maxKeyBound();
> RowPosition rightPosition = range.left.maxKeyBound();
> should be changed to:
> RowPosition leftPosition = range.left.maxKeyBound();
> RowPosition rightPosition = range.right.maxKeyBound();
> After that fix the output of nodetool is correct and the whole ring is split
> into small mappers.
> The other half of the ring works fine because of extra 'if' in the code:
> int right = Range.isWrapAround(range.left, range.right)...
> This causes that the bug does not show up in one-node cluster or in the
> "last" ring partition in muli-node clusters.
> Can anyone look at it and verify my thoughts? I'm rather new to Cassandra.
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