[jira] [Commented] (PIG-3680) A new type of EvalFunc, TransactionalEvalFunc, would be useful

["Nezih Yigitbasi (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PIG-3680?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13877886#comment-13877886 ] 

Nezih Yigitbasi commented on PIG-3680:
--------------------------------------

I have seen that EvalFunc class has a finish() method that can be used for cleanup. Initialization can be done in exec() once by keeping track of whether we have already initialized or not. So overall it seems that EvalFunc can already imitate such a transactional context, except finish() doesn't tell whether there was any error during the map phase. 

> A new type of EvalFunc, TransactionalEvalFunc, would be useful
> --------------------------------------------------------------
>
>                 Key: PIG-3680
>                 URL: https://issues.apache.org/jira/browse/PIG-3680
>             Project: Pig
>          Issue Type: New Feature
>            Reporter: Nezih Yigitbasi
>            Assignee: Nezih Yigitbasi
>            Priority: Minor
>
> I think a new type of EvalFunc that has some notion of a transactional context would be very useful. This new TransactionalEvalFunc abstract class should have methods like initialize, onSuccess, and onFailure to mark the transaction boundaries. Such EvalFuncs would be useful for interacting with external resources. For example, to delete rows from an existing hbase table such a transactional UDF would be useful. Of course we can imitate this with a StoreFunc, but conceptually StoreFunc's are restricted to writes. If the community thinks this will be useful, I am ready to spend time on this..



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