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https://issues.apache.org/jira/browse/PIG-928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12891357#action_12891357
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Aniket Mokashi commented on PIG-928:
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bq. I am still not convinced about the changes required in POUserFunc. That
logic should really be a part of pythonToPig(pyObject). If python UDF is
returning byte[], it should be turned into DataByteArray before it gets back
into Pig's pipeline. And if we do that conversion in pythonToPig() (which is a
right place to do it) we will need no changes in POUserFunc.
I agree that it is better to move computation on JythonFunction side
(JythonUtils) for type checking and should provide more type safety to avoid
user defined types complexity. But I would still go for changes in POUserFunc
for result.result for the case defined in above example (removing byte[]
scenario).
bq. Instead of instanceof, doing class equality test will be a wee-bit faster.
Like instead of (pyObject instanceof PyDictionary) do pyobject.getClass() ==
PyDictionary.class. Obviously, it will work when you know exact target class
and not for the derived ones.
Jython code has derived classes for each of the basic Jython types, though they
aren't used for most of the types as of now, they may start returning these
derived objects (PyTupleDerived) in their future implementation, in which case
we might break our code. Also, PyLongDerived are already used inside the code.
__tojava__ function just returns the proxy java object until we ask for a
specific type of object. I think its better to use instanceof instead of class
equality here.
bq. For register command, we need to test not only for functionality but for
regressions as well. Look at TestGrunt.java in test package to get an idea how
to write test for it.
Code path for .jar registration is identical to old code, except that it doesnt
"use" any engine or namespace.
bq. Also what will happen if user returned a nil python object (null equivalent
of Java) from UDF. It looks to me that will result in NPE. Can you add a test
for that and similar test case from pigToPython()
A java null object will be turned into PyNone object but __tojava__ function
will always returns the special object Py.NoConversion if this PyObject can
not be converted to the desired Java class.
> UDFs in scripting languages
> ---------------------------
>
> Key: PIG-928
> URL: https://issues.apache.org/jira/browse/PIG-928
> Project: Pig
> Issue Type: New Feature
> Reporter: Alan Gates
> Assignee: Aniket Mokashi
> Fix For: 0.8.0
>
> Attachments: calltrace.png, package.zip, PIG-928.patch,
> pig-greek.tgz, pig.scripting.patch.arnab, pyg.tgz, RegisterPythonUDF3.patch,
> RegisterPythonUDF4.patch, RegisterPythonUDF_Final.patch,
> RegisterPythonUDFFinale.patch, RegisterPythonUDFFinale3.patch,
> RegisterPythonUDFFinale4.patch, RegisterPythonUDFFinale5.patch,
> RegisterPythonUDFLatest.patch, RegisterScriptUDFDefineParse.patch,
> scripting.tgz, scripting.tgz, test.zip
>
>
> It should be possible to write UDFs in scripting languages such as python,
> ruby, etc. This frees users from needing to compile Java, generate a jar,
> etc. It also opens Pig to programmers who prefer scripting languages over
> Java.
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