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From "Jeremy Hanna (JIRA)" <j...@apache.org>
Subject [jira] Updated: (CASSANDRA-1042) ColumnFamilyRecordReader returns duplicate rows
Date Thu, 20 May 2010 23:34:19 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-1042?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jeremy Hanna updated CASSANDRA-1042:
------------------------------------

    Attachment: cassandra.tar.gz

In order to facilitate reproducing the problem, I'm attaching my cassandra data directory
tar/gzed up.

There are 4 rows in the cassandra instance.  If you modify WordCountSetup to change TEST_COUNT
from 4 to 1, then run WordCount, you will find that Cassandra trunk will count 7 occurrences
instead of 4.  You can also debug on the line I mentioned previously to see what describe_splits
receives and then outputs.

Just wanted to facilitate reproducing the problem.

> ColumnFamilyRecordReader returns duplicate rows
> -----------------------------------------------
>
>                 Key: CASSANDRA-1042
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1042
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Hadoop
>    Affects Versions: 0.6
>            Reporter: Joost Ouwerkerk
>            Assignee: Jonathan Ellis
>             Fix For: 0.6.2
>
>         Attachments: cassandra.tar.gz
>
>
> There's a bug in ColumnFamilyRecordReader that appears when processing a single split
(which happens in most tests that have small number of rows), and potentially in other cases.
 When the start and end tokens of the split are equal, duplicate rows can be returned.
> Example with 5 rows:
> token (start and end) = 53193025635115934196771903670925341736
> Tokens returned by first get_range_slices iteration (all 5 rows):
>  16955237001963240173058271559858726497
>  40670782773005619916245995581909898190
>  99079589977253916124855502156832923443
>  144992942750327304334463589818972416113
>  166860289390734216023086131251507064403
> Tokens returned by next iteration (first token is last token from
> previous, end token is unchanged)
>  16955237001963240173058271559858726497
>  40670782773005619916245995581909898190
> Tokens returned by final iteration  (first token is last token from
> previous, end token is unchanged)
>  [] (empty)
> In this example, the mapper has processed 7 rows in total, 2 of which
> were duplicates.

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