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From "Jason Lowe (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-9622) bzip2 codec can drop records when reading data in splits
Date Wed, 05 Jun 2013 21:33:21 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-9622?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jason Lowe updated HADOOP-9622:
-------------------------------

    Attachment: HADOOP-9622-testcase.patch

Attaching a testcase for the problem, which requires the same input file as used in one of
Pig's bzip2 unit tests, [blockEndingInCR.txt.bz2|https://issues.apache.org/jira/secure/attachment/12438881/blockEndingInCR.txt.bz2].
 Drop the file into hadoop-common-project/hadoop-common/src/test/resources/ and the unit test
can be run via Maven.

I've also manually verified the loss of records via a simple streaming job:

hadoop jar hadoop-*/share/hadoop/tools/lib/hadoop-streaming*.jar -Dmapreduce.input.fileinputformat.split.minsize=136498
-Dmapreduce.job.maps=3 -input blockEndingInCR.txt.bz2 -output streamout -mapper cat -reducer
NONE

Examining the output of the job shows that the record after the carriage return in the file
was dropped.  Running a similar streaming job with only one map (no splits) shows the record
is not dropped.
                
> bzip2 codec can drop records when reading data in splits
> --------------------------------------------------------
>
>                 Key: HADOOP-9622
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9622
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: io
>    Affects Versions: 2.0.4-alpha, 0.23.8
>            Reporter: Jason Lowe
>            Priority: Critical
>         Attachments: HADOOP-9622-testcase.patch
>
>
> Bzip2Codec.BZip2CompressionInputStream can cause records to be dropped when reading them
in splits based on where record delimiters occur relative to compression block boundaries.
> Thanks to [~knoguchi] for discovering this problem while working on PIG-3251.

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