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From "Alan Gates (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-1112) FLATTEN eliminates the alias
Date Sat, 06 Nov 2010 00:08:42 GMT

    [ https://issues.apache.org/jira/browse/PIG-1112?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12928889#action_12928889
] 

Alan Gates commented on PIG-1112:
---------------------------------

Daniel, I don't understand the choice here.  I think we agreed that if the user specifies
(third, second) as the schema then we take that to mean there are two bytearray fields and
we project them to guarantee this.  So

{code}
B = FOREACH A GENERATE first,FLATTEN(ladder) as third,second;
{code}

will now be equivalent to
{code}
Bprime = FOREACH A GENERATE first,FLATTEN(ladder);
B = FOREACH Bprime GENERATE first, $1 as third, $2 as second;
{code}

> FLATTEN eliminates the alias
> ----------------------------
>
>                 Key: PIG-1112
>                 URL: https://issues.apache.org/jira/browse/PIG-1112
>             Project: Pig
>          Issue Type: Bug
>            Reporter: Ankur
>            Assignee: Alan Gates
>             Fix For: 0.9.0
>
>
> If schema for a field of type 'bag' is partially defined then FLATTEN() incorrectly eliminates
the field and throws an error. 
> Consider the following example:-
> A = LOAD 'sample' using PigStorage() as (first:chararray, second:chararray, ladder:bag{});
             
> B = FOREACH A GENERATE first,FLATTEN(ladder) as third,second;                       
           
> C = GROUP B by (first,third);
> This throws the error
>  ERROR org.apache.pig.tools.grunt.Grunt - ERROR 1000: Error during parsing. Invalid alias:
third in {first: chararray,second: chararray}

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