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From "Pete Wyckoff (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4065) support for reading binary data from flat files
Date Mon, 08 Sep 2008 21:47:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12629305#action_12629305
] 

Pete Wyckoff commented on HADOOP-4065:
--------------------------------------

Nice. Will the TFileRecordReader fit into this paradigm?  How were you going to implement
the TFileRecordReader?

TFile is very similar to TRecordStream - but more full featured - sorted and seek by key.
But, TRecordStream is meant to be readable/writable in many languages (first cut c++, java,
python and perl). It's primary use case is non-hadoop - just a robust way of logging data,
but secondarily, there's no reason not to enable directly reading/writing to one from Hadoop
as it's a waste to open one, read it and write it out as a TFile or SF if one doesn't need
the richer functionality that sequence file and tfile support.



-- pete



> support for reading binary data from flat files
> -----------------------------------------------
>
>                 Key: HADOOP-4065
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4065
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>            Reporter: Joydeep Sen Sarma
>
> like textinputformat - looking for a concrete implementation to read binary records from
a flat file (that may be compressed).
> it's assumed that hadoop can't split such a file. so the inputformat can set splittable
to false.
> tricky aspects are:
> - how to know what class the file contains (has to be in a configuration somewhere).
> - how to determine EOF (would be nice if hadoop can determine EOF and not have the deserializer
throw an exception  (which is hard to distinguish from a exception due to corruptions?)).
this is easy for non-compressed streams - for compressed streams - DecompressorStream has
a useful looking getAvailable() call - except the class is marked package private.

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