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https://issues.apache.org/jira/browse/PIG-972?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12875390#action_12875390
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Aniket Mokashi commented on PIG-972:
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Approach mentioned above seems to work.
Here are some proposals on semantics of nested describe-
>a = load '1.txt' as (a0:int, a1:int);
>b = group a by $0;
Proposal 1- Explicit describe.
>c = foreach b { d = order a by $0; describe d; e = ...; generate d.$0 ...;}
(1a:Instantaneous responce - describes d after parsing above statement)
>describe c;
Prints schema for c and d (but not e)
Adv - Can select which one of nestedAlias to describe.
Disadv - Extra typing.
Proposal 2:- Implicit describe (no describe nested statements)
>c = foreach b { d = order a by $0; e = ...; generate d.$0 ...;}
>describe c;
Describes c, d and e;
Adv- less typing
Disadv- extra prints
(2a - describe c prints for c, d and e. Also describe c->d to describe nested
d)
(2b - describe c prints for c only. describe c-> d to describe nested d).
Alan/Olga, Let me know your comments on this,
> Make describe work with nested foreach
> --------------------------------------
>
> Key: PIG-972
> URL: https://issues.apache.org/jira/browse/PIG-972
> Project: Pig
> Issue Type: Improvement
> Reporter: Olga Natkovich
> Assignee: Aniket Mokashi
> Fix For: 0.8.0
>
>
> Currently Parser can't deal with that. This is because describe is part of
> Grunt parser while the rest of nested foreach is handled by the QueryParser
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