[jira] Updated: (PIG-1434) Allow casting relations to scalars

["Aniket Mokashi (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/PIG-1434?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Aniket Mokashi updated PIG-1434:
--------------------------------

    Attachment: ScalarImpl1.patch

LOScalar keeps track of the scalars in the logical plan along with the reference to the scalar alias.
During compilation, we add LOStores to respective scalars, we also merge plans as needed.
POScalar is later replaced by POUserFunc and appropriate dependency is added between the MROpers.
Tested with store, dump, explain.

> 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
>
>
> 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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