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https://issues.apache.org/jira/browse/PIG-3419?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13749014#comment-13749014
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Dmitriy V. Ryaboy commented on PIG-3419:
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Rohini, I want to reiterate that this patch has NO tez dependencies (if it
does, that's a bug). The intention is not to make Tez possible. It's to make
pluggable execution engines possible; and I do not want that functionality to
be tied to a tez branch that will be unstable and in heavy development for the
foreseeable future. This work will be immediately useful for the Spork (pig on
spark) branch, for example.
Also, it allows people to work with new runtimes *without modifying Pig*. So
Tez-on-Pig doesn't even have to be done as a branch of this project, someone
can go an experiment completely independently.
For these reasons, I would like it in trunk.
You make a great point about the danger of changing exceptions, public methods,
etc. I believe that most of these are project-public, and annotated as such. Do
you have specific methods you are concerned about? Ideally we would change as
little as possible for the end user.
Dmitriy
> 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
> Attachments: execengine.patch, mapreduce_execengine.patch,
> stats_scriptstate.patch, test_failures.txt, test_suite.patch,
> updated-8-22-2013-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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