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From "David Ciemiewicz (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-760) Serialize schemas for PigStorage() and other storage types.
Date Thu, 22 Oct 2009 22:43:59 GMT

    [ https://issues.apache.org/jira/browse/PIG-760?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12768948#action_12768948
] 

David Ciemiewicz commented on PIG-760:
--------------------------------------

@Dimitry:

> Still flat-schemas only, haven't gotten around to wrestling the Jackson Parser on this
one. David - do you need nested schemas?

No, at this time, and for the foreseeable future, I do not need nested schemes (hierarchical
schemes) in relationship to PigStorage.

In general, PigStorage users are doing single atomic value per column. So your current implementation
sounds like it will suffice for now, with appropriate caveats in any docs.

BTW, is there a pointer to documentation of the .pig_schema file likes like.  Guess there
should be one for .pig_header too. :-)

> Serialize schemas for PigStorage() and other storage types.
> -----------------------------------------------------------
>
>                 Key: PIG-760
>                 URL: https://issues.apache.org/jira/browse/PIG-760
>             Project: Pig
>          Issue Type: New Feature
>            Reporter: David Ciemiewicz
>            Assignee: Dmitriy V. Ryaboy
>             Fix For: 0.6.0
>
>         Attachments: pigstorageschema-2.patch, pigstorageschema.patch
>
>
> I'm finding PigStorage() really convenient for storage and data interchange because it
compresses well and imports into Excel and other analysis environments well.
> However, it is a pain when it comes to maintenance because the columns are in fixed locations
and I'd like to add columns in some cases.
> It would be great if load PigStorage() could read a default schema from a .schema file
stored with the data and if store PigStorage() could store a .schema file with the data.
> I have tested this out and both Hadoop HDFS and Pig in -exectype local mode will ignore
a file called .schema in a directory of part files.
> So, for example, if I have a chain of Pig scripts I execute such as:
> A = load 'data-1' using PigStorage() as ( a: int , b: int );
> store A into 'data-2' using PigStorage();
> B = load 'data-2' using PigStorage();
> describe B;
> describe B should output something like { a: int, b: int }

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