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https://issues.apache.org/jira/browse/PIG-1434?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12886825#action_12886825
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Daniel Dai commented on PIG-1434:
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We also need to enforce C only have one part file to do the check (use limit to
achieve it).
{code}
C = limit C 2;
C = foreach C generate CheckSingular(*);
Z = join X by 1, C by 1 using 'replicated';
Y = foreach Z generate X::$1/(long) C.count, X::$2-(long) C.max;
{code}
> 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
>
>
> 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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