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From "Alan Gates (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-1461) support union operation that merges based on column names
Date Tue, 27 Jul 2010 19:32:16 GMT

    [ https://issues.apache.org/jira/browse/PIG-1461?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12892903#action_12892903
] 

Alan Gates commented on PIG-1461:
---------------------------------

+1 on Thejas comment that so far using indicates implementation not semantic change and it's
best to keep it that way.  "union onschema" seems fine, as this seems equivalent to "join
outer".

> support union operation that merges based on column names
> ---------------------------------------------------------
>
>                 Key: PIG-1461
>                 URL: https://issues.apache.org/jira/browse/PIG-1461
>             Project: Pig
>          Issue Type: New Feature
>          Components: impl
>    Affects Versions: 0.8.0
>            Reporter: Thejas M Nair
>            Assignee: Thejas M Nair
>             Fix For: 0.8.0
>
>
> When the data has schema, it often makes sense to union on column names in schema rather
than the position of the columns. 
> The behavior of existing union operator should remain backward compatible .
> This feature can be supported using either a new operator or extending union to support
'using' clause . I am thinking of having a new operator called either unionschema or merge
. Does anybody have any other suggestions for the syntax ?
> example -
> L1 = load 'x' as (a,b);
> L2 = load 'y' as (b,c);
> U = unionschema L1, L2;
> describe U;
> U: {a:bytearray, b:byetarray, c:bytearray}

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