[jira] Commented: (HIVE-471) A UDF for simple reflection

["Ashish Thusoo (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-471?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12739965#action_12739965 ] 

Ashish Thusoo commented on HIVE-471:
------------------------------------

Sorry in the delay in responding. Zheng would be able to give you better answers here.

For the error that you are getting I think you have to end up using ObjectInspectorConvertors I think but Zheng can confirm. 

For different return type you could take a look at the GenericUDFCase.java and look at how it defines ReturnObjectInspectorResolver. Similar to that you could have a ReflectionObjectInspectorResolver which returns the proper ObjectInspector corresponding to the return type.

ObjectInspectors essentially encode the type and the in memory formats of the object. Let us know if you  are able to make progress by following GenericUDFCase.java.

> A UDF for simple reflection
> ---------------------------
>
>                 Key: HIVE-471
>                 URL: https://issues.apache.org/jira/browse/HIVE-471
>             Project: Hadoop Hive
>          Issue Type: New Feature
>          Components: Query Processor
>            Reporter: Edward Capriolo
>            Assignee: Edward Capriolo
>            Priority: Minor
>             Fix For: 0.4.0
>
>         Attachments: hive-471-gen.diff, hive-471.diff
>
>
> There are many methods in java that are static and have no arguments or can be invoked with one simple parameter. More complicated functions will require a UDF but one generic one can work as a poor-mans UDF.
> {noformat}
> SELECT reflect("java.lang.String", "valueOf", 1), reflect("java.lang.String", "isEmpty")
> FROM src LIMIT 1;
> {noformat}

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