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https://issues.apache.org/jira/browse/PIG-1461?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12892892#action_12892892
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Thejas M Nair commented on PIG-1461:
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The syntax - " union ... using 'merge' " introduces a new use of the " using
'...' " clause. So far this clause has been used to indicate the implementation
algorithm and it did not have any impact on the semantics.
Instead a key word might be better if we are trying to avoid introducing
another top level operator, similar to the case of outer joins - eg - " union
onschema L1, L2;"
More suggestions/opinions on the syntax for this feature are welcome.
> 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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