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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 Thu, 18 Sep 2008 02:51:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12632067#action_12632067
] 

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

bq. In either case, changes to the serialization framework seems like serious overkill.

you are right - I don't know why I went that direction. It should be exactly the oppostite
of the way I coded it up.

All one needs is some way of getting SerializationContext information (to instantiate the
right Serialization Object and then the actual subclass we want to deserialize; e.g., Record/MyRecordObj).
[this was called RowSource in joy's code example]

And then a simple record reader that uses that info to instantiate a deserializer and done.

No changes to the serialization framework.

I actually have that with unit tests and just need to clean up the documentation and such.

-- 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
>         Attachments: HADOOP-4065.0.txt, HADOOP-4065.1.txt, ThriftFlatFile.java
>
>
> 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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