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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Updated: (CASSANDRA-1042) ColumnFamilyRecordReader returns duplicate rows
Date Mon, 19 Jul 2010 15:51:53 GMT

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

Jonathan Ellis updated CASSANDRA-1042:
--------------------------------------

    Attachment: 1042-v2.txt

v2 attached:

 - removes wrapped-range handling from CFS.getRangeSlice, since StorageProxy always unwraps
first
 - adds (initially failing) system test exercising wrapped-range path
 - adds sorting of unwrapped, restricted ranges relative to the original query range [this
is the bug fix]


> 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, 1042-v2.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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