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From "Benjamin Reed (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-42) Pig should be able to split Gzip files like it can split Bzip files
Date Fri, 07 Dec 2007 18:01:43 GMT

    [ https://issues.apache.org/jira/browse/PIG-42?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12549494
] 

Benjamin Reed commented on PIG-42:
----------------------------------

The patch is not ready to commit yet. It's a work in progress patch. I talked to Utkarash
about this and it's missing a termination of the split. Currently each split will not terminate
correctly.There is a termination hook that bzip uses that I need to latch into.

Basically here are the things I need to add to finish:

1) Terminate split processing correctly
2) Add test cases
3) Encode block size as part of the header so that we can get almost "perfect" splits. (For
example a file that is compressed as 128M blocks should not be split on 64M boundaries even
if the block size of the filesystem is 128M.)

I'll try to get a committable patch this weekend.





> Pig should be able to split Gzip files like it can split Bzip files
> -------------------------------------------------------------------
>
>                 Key: PIG-42
>                 URL: https://issues.apache.org/jira/browse/PIG-42
>             Project: Pig
>          Issue Type: Improvement
>          Components: impl
>            Reporter: Benjamin Reed
>         Attachments: gzip.patch
>
>
> It would be nice to be able to split gzip files like we can split bzip files. Unfortunately,
we don't have a sync point for the split in the gzip format.
> Gzip file format supports the notion of concatenate gzipped files. When gzipped files
are concatenated together they are treated as a single file. So to make a gzipped file splittable
we can used an empty compressed file with some salt in the headers as a sync signature. Then
we can make the gzip file splittable by using this sync signature between compressed segments
of the file.

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