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From "Rohini Palaniswamy (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PIG-4608) FOREACH ... UPDATE
Date Tue, 16 Jan 2018 22:55:00 GMT

    [ https://issues.apache.org/jira/browse/PIG-4608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16327955#comment-16327955
] 

Rohini Palaniswamy commented on PIG-4608:
-----------------------------------------

bq. As for the 'update val AS col' versus 'update col BY val', I think the former looks less
confusing to a current pig user.
Agree and prefer usage of AS. Also BY does not make sense grammatically. It should either
be AS (update val AS col) or WITH (update col WITH val). 

bq. As for delete, I somehow prefer using drop.
I prefer drop as well as that is similar to the alter table drop column of SQL. Delete is
generally used for rows.





> FOREACH ... UPDATE
> ------------------
>
>                 Key: PIG-4608
>                 URL: https://issues.apache.org/jira/browse/PIG-4608
>             Project: Pig
>          Issue Type: New Feature
>            Reporter: Haley Thrapp
>            Priority: Major
>
> I would like to propose a new command in Pig, FOREACH...UPDATE.
> Syntactically, it would look much like FOREACH … GENERATE.
> Example:
> Input data:
> (1,2,3)
> (2,3,4)
> (3,4,5)
> -- Load the data
> three_numbers = LOAD 'input_data'
> USING PigStorage()
> AS (f1:int, f2:int, f3:int);
> -- Sum up the row
> updated = FOREACH three_numbers UPDATE
> 5 as f1,
> f1+f2 as new_sum
> ;
> Dump updated;
> (5,2,3,3)
> (5,3,4,5)
> (5,4,5,7)
> Fields to update must be specified by alias. Any fields in the UPDATE that do not match
an existing field will be appended to the end of the tuple.
> This command is particularly desirable in scripts that deal with a large number of fields
(in the 20-200 range). Often, we need to only make modifications to a few fields. The FOREACH
... UPDATE statement, allows the developer to focus on the actual logical changes instead
of having to list all of the fields that are also being passed through.
> My team has prototyped this with changes to FOREACH ... GENERATE. We believe this can
be done with changes to the parser and the creation of a new LOUpdate. No physical plan changes
should be needed because we will leverage what LOGenerate does.



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