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
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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