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https://issues.apache.org/jira/browse/PIG-3419?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13767615#comment-13767615
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Rohini Palaniswamy commented on PIG-3419:
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Dmitriy,
I am not arguing about adding interfaces to enable other frameworks. If you
take the LoadFuncs case, a lot of design and work went into that
(http://wiki.apache.org/pig/LoadStoreRedesignProposal) in coming up with and
finalizing the interfaces and there were Loaders and Storers changed or written
with the design of the new interfaces before the new interfaces were released.
In this case we have added the interfaces without doing something like that and
putting it in a release. That was my concern.
As Bill suggests if we mark and agree that the new interfaces are unstable and
bound to change and no backward compatibility will be provided, then I am good.
Because when we actually get to Tez or Spork implementation (not POC), I am
sure these are bound to change or more new methods are required.
> Pluggable Execution Engine
> ---------------------------
>
> Key: PIG-3419
> URL: https://issues.apache.org/jira/browse/PIG-3419
> Project: Pig
> Issue Type: New Feature
> Affects Versions: 0.12
> Reporter: Achal Soni
> Assignee: Achal Soni
> Priority: Minor
> Fix For: 0.12
>
> Attachments: execengine.patch, mapreduce_execengine.patch,
> stats_scriptstate.patch, test_failures.txt, test_suite.patch,
> updated-8-22-2013-exec-engine.patch, updated-8-23-2013-exec-engine.patch,
> updated-8-27-2013-exec-engine.patch, updated-8-28-2013-exec-engine.patch,
> updated-8-29-2013-exec-engine.patch
>
>
> In an effort to adapt Pig to work using Apache Tez
> (https://issues.apache.org/jira/browse/TEZ), I made some changes to allow for
> a cleaner ExecutionEngine abstraction than existed before. The changes are
> not that major as Pig was already relatively abstracted out between the
> frontend and backend. The changes in the attached commit are essentially the
> barebones changes -- I tried to not change the structure of Pig's different
> components too much. I think it will be interesting to see in the future how
> we can refactor more areas of Pig to really honor this abstraction between
> the frontend and backend.
> Some of the changes was to reinstate an ExecutionEngine interface to tie
> together the front end and backend, and making the changes in Pig to delegate
> to the EE when necessary, and creating an MRExecutionEngine that implements
> this interface. Other work included changing ExecType to cycle through the
> ExecutionEngines on the classpath and select the appropriate one (this is
> done using Java ServiceLoader, exactly how MapReduce does for choosing the
> framework to use between local and distributed mode). Also I tried to make
> ScriptState, JobStats, and PigStats as abstract as possible in its current
> state. I think in the future some work will need to be done here to perhaps
> re-evaluate the usage of ScriptState and the responsibilities of the
> different statistics classes. I haven't touched the PPNL, but I think more
> abstraction is needed here, perhaps in a separate patch.
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