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https://issues.apache.org/jira/browse/PIG-4608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16327686#comment-16327686
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Koji Noguchi commented on PIG-4608:
-----------------------------------
For now, can we just require separate statements for update and delete ?
Also, not too excited with the use of {{AS}} for specifying which field to
update.
So far, "as" has been used for only naming the fields.
Wondering if we can require the field-name upfront.
Instead of
* {{c = foreach a update "prefix"+x as x}}
can we write as
* {{c = foreach a update x by "prefix"+x}};
As for delete, I somehow prefer using {{drop}}.
[~daijy], love to hear your thoughts on this.
> 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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