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https://issues.apache.org/jira/browse/PIG-2421?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13171353#comment-13171353
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Alan Gates commented on PIG-2421:
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BTW, thanks both Julien and Dmitriy for the feedback.
> EvalFuncs need redesigned
> -------------------------
>
> Key: PIG-2421
> URL: https://issues.apache.org/jira/browse/PIG-2421
> Project: Pig
> Issue Type: New Feature
> Components: impl
> Affects Versions: 0.11
> Reporter: Alan Gates
> Assignee: Alan Gates
> Attachments: PIG-newudf.patch, examples.patch
>
>
> The current EvalFunc interface (and associated Algebraic and Accumulator
> interfaces) have grown unwieldy. In particular, people have noted the
> following issues:
> # Writing a UDF requires a lot of boiler plate code.
> # Since UDFs always pass a tuple, users are required to manage their own type
> checking for input.
> # Declaring schemas for output data is confusing.
> # Writing a UDF that accepts multiple different parameters (using
> getArgToFuncMapping) is confusing.
> # Using Algebraic and Accumulator interfaces often entails duplicating code
> from the initial implementation.
> # UDF implementors are exposed to the internals of Pig since they have to
> know when to return a tuple (Initial, Intermediate) and when not to (exec,
> Final).
> # The separation of Initial, Intermediate, and Final into separate classes
> forces code duplication and makes it hard for UDFs in other languages to use
> those interfaces.
> # There is unused code in the current interface that occasionally causes
> confusion (e.g. isAsynchronous)
> Any change must be done in a way that allows existing UDFs to continue
> working essentially forever.
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