[jira] [Commented] (CALCITE-4942) Deprecate Bolier plate for Rel Metadata

["Jacques Nadeau (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-4942?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17460919#comment-17460919 ] 

Jacques Nadeau commented on CALCITE-4942:
-----------------------------------------

Glad you're picking this up. Will be interested how you propose doing this without having breaking changes (and refactoring reflection reliance on existing getDef() functionality)



> Deprecate Bolier plate for Rel Metadata
> ---------------------------------------
>
>                 Key: CALCITE-4942
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4942
>             Project: Calcite
>          Issue Type: Improvement
>            Reporter: James Starr
>            Assignee: James Starr
>            Priority: Major
>
> To define a Rel metadata type you need to create 2 class, 2 methods and a static variable.  However, current implementation of RelMetadata back by Janino only require the Handler class a single method signature.  The current metadata handler interface also has a generic that provides no type safety through out code. 
> Currently to define a rel metadata type:
> {code:java}
> public class MyMetadata extends Metadata {
>   MetadataDef DEF = ...
>  
>  VALUE myMethod1();
>   class Handler extends RelHandler<MyMetadata> {
>     VALUE myMethod2(RelNode, MetadataQuery)
>   }
> }
> {code}
> What is actually needed to define a rel metadata type:
> {code:java}
> class MyMetadataHandler extends RelHandler {
>   VALUE myMethod(RelNode, MetadataQuery)
> }
> {code}



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