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https://issues.apache.org/jira/browse/PIG-4608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16327736#comment-16327736
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Kevin J. Price commented on PIG-4608:
-------------------------------------
This is Yahoo-centric, but would it be possible to grep our logs for existing
pig jobs and see how many of them have keyword conflicts with 'update',
'delete', 'drop', etc? I'm indifferent on 'delete' versus 'drop', but it'd be
interesting to know which one would impact fewer existing scripts.
As for the 'update val AS col' versus 'update col BY val', I think the former
looks less confusing to a current pig user. 'BY' only gets used currently for
key ordering in groups and joins, whereas 'AS' is already used for value
assignment. I agree that there's a difference between 'GENERATE val AS col' and
'UPDATE val AS col', but it's a fairly philosophical difference from the user's
perspective. In both cases, they want col to have the value val after the
statement, so having the same syntax makes sense.
> 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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