hadoop-pig-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Dmitriy V. Ryaboy (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-1434) Allow casting relations to scalars
Date Fri, 02 Jul 2010 21:12:50 GMT

    [ https://issues.apache.org/jira/browse/PIG-1434?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12884807#action_12884807
] 

Dmitriy V. Ryaboy commented on PIG-1434:
----------------------------------------

I think it's important in this particular case to ensure that C only contains one tuple, since
multiple tuples will lead to very confusing output.
Maybe

{code}
C = LIMIT C 1;
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}

(this is where an optimization that notes that you don't need m/r boundary if the relation
you are limiting only has one partition would come in handy).

> 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

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message