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https://issues.apache.org/jira/browse/PIG-1634?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12913115#action_12913115
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Alan Gates commented on PIG-1634:
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In Pig's semantics c.group, c.foo, and c.bar are all separate columns, and only
the first one is $0. Because the bags from the cogroup contain all columns in
the row (not just non-key columns) foo is in a and bar in b.
Changing something like this would be a radical shift of Pig semantics.
> Multiple names for the "group" field
> ------------------------------------
>
> Key: PIG-1634
> URL: https://issues.apache.org/jira/browse/PIG-1634
> Project: Pig
> Issue Type: New Feature
> Affects Versions: 0.1.0, 0.2.0, 0.3.0, 0.4.0, 0.5.0, 0.6.0, 0.7.0
> Reporter: Viraj Bhat
>
> I am hoping that in Pig if I type
> {quote} c = cogroup a by foo, b by bar", the fields c.group, c.foo and c.bar
> should all map to c.$0 {quote}
> This would improve the readability of the Pig script.
> Here's a real usecase:
> {code}
> ---
> pages = LOAD 'pages.dat' AS (url, pagerank);
> visits = LOAD 'user_log.dat' AS (user_id, url);
> page_visits = COGROUP pages BY url, visits BY url;
> frequent_visits = FILTER page_visits BY COUNT(visits) >= 2;
> answer = FOREACH frequent_visits GENERATE url, FLATTEN(pages.pagerank);
> ---
> {code}
> (The important part is the final GENERATE statement, which references the
> field "url", which was the grouping field in the earlier COGROUP.) To get it
> to work I have to write it in a less intuitive way.
> Maybe with the new parser changes in Pig 0.9 it would be easier to specify
> that.
> Viraj
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