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From "Keith Turner (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-4500) Implement visibility histograms as a table feature
Date Wed, 19 Oct 2016 16:46:58 GMT


Keith Turner commented on ACCUMULO-4500:

Re passing in an instance of a Function, how can we run the function on remote JVMs?  We could
take the class name from the instance and use that to instantiate on remote JVMs. The following
are two possible issues with taking the class name from the instance.

 * Anonymous inner classes (AIC) : If the user passes in Foo$1, it could be that the same
AIC is Foo$2 on a remote JVM. This could happen when running a slightly different version
of the code on the remote.  Also if the Anonymous inner class is not static, could be tricky
to instantiate on remote JVM. 
 * Lambdas : Are not inner classes[1].  I have no idea if you can safely serialize[2] lambdas
between class files generated from different versions of code???

I have wanted to look into what Spark does, but have not had a chance to dig into the details.
 I strongly suspect Spark can make certain assumptions based on the fact that all JVMs are
running the exact same version of user code.  In this case its reasonable to expect an AIC
to have the same name across JVMs.   I don't think we should assume Accumulo client and server
processes are running the exact same version of user code.

It seems given our circumstances that using a class name instead of an instance would be safer.
 I suppose we could just dissallow AICs (throw an exception).  Not sure about lambdas.


> Implement visibility histograms as a table feature
> --------------------------------------------------
>                 Key: ACCUMULO-4500
>                 URL:
>             Project: Accumulo
>          Issue Type: New Feature
>          Components: client, tserver
>            Reporter: Josh Elser
> Add support to quickly extract a histogram of all of the visibilities stored in an Accumulo

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