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https://issues.apache.org/jira/browse/PIG-1434?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Richard Ding updated PIG-1434:
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Status: Resolved (was: Patch Available)
Hadoop Flags: [Reviewed]
Resolution: Fixed
Tags: documentation
The patch is committed to trunk. Thanks Aniket for contributing this feature.
> Allow casting relations to scalars
> ----------------------------------
>
> Key: PIG-1434
> URL: https://issues.apache.org/jira/browse/PIG-1434
> Project: Pig
> Issue Type: Improvement
> Reporter: Olga Natkovich
> Assignee: Aniket Mokashi
> Fix For: 0.8.0
>
> Attachments: scalarImpl.patch, ScalarImpl1.patch, ScalarImpl5.patch,
> ScalarImplFinale.patch, ScalarImplFinale1.patch, ScalarImplFinaleRebase.patch
>
>
> This jira is to implement a simplified version of the functionality described
> in https://issues.apache.org/jira/browse/PIG-801.
> The proposal is to allow casting relations to scalar types in foreach.
> Example:
> A = load 'data' as (x, y, z);
> B = group A all;
> C = foreach B generate COUNT(A);
> .....
> X = ....
> Y = foreach X generate $1/(long) C;
> Couple of additional comments:
> (1) You can only cast relations including a single value or an error will be
> reported
> (2) Name resolution is needed since relation X might have field named C in
> which case that field takes precedence.
> (3) Y will look for C closest to it.
> Implementation thoughts:
> The idea is to store C into a file and then convert it into scalar via a UDF.
> I believe we already have a UDF that Ben Reed contributed for this purpose.
> Most of the work would be to update the logical plan to
> (1) Store C
> (2) convert the cast to the UDF
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