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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-1042) ColumnFamilyRecordReader returns duplicate rows
Date Mon, 12 Jul 2010 01:13:52 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1042?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12887256#action_12887256
] 

Jonathan Ellis commented on CASSANDRA-1042:
-------------------------------------------

Jeremy pointed out that the sorting that removed by the original patch here is sorting in
raw token order rather than taking into account the requested start token.  I think that's
our problem, although I'm not sure why my unit test isn't running into that.

> 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: Jeremy Hanna
>             Fix For: 0.6.4
>
>         Attachments: 1042-0_6.txt, 1042-test.txt, Cassandra-1042-0_6-branch.patch.txt,
CASSANDRA-1042-trunk.patch.txt, cassandra.tar.gz, duplicate_keys.rtf
>
>
> 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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