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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-1245) Introduce TypeHints for Java API operators
Date Wed, 26 Nov 2014 19:32:12 GMT

    [ https://issues.apache.org/jira/browse/FLINK-1245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14226688#comment-14226688
] 

ASF GitHub Bot commented on FLINK-1245:
---------------------------------------

Github user StephanEwen commented on the pull request:

    https://github.com/apache/incubator-flink/pull/203#issuecomment-64698910
  
    I like the direction of this pull request. Here are some thought what we could improve:
    
      - Keeping the UnknownTypeInfo all the way and actually trying to work with it will shadow
problems. At much later points, when someone tries to use a POJO field on the type info, an
error will occur, at a point that is disconnected from the source of the problem.
    
      - How about we rename the `UnknownTypeInfo` to `MissingTypeInfo` and use it only as
a place-holder for the `returns()` hint method, which exchanges that type info by the proper
one.
    
      - We could make sure that type extraction failures are recognized early, by having the
`getType()` method on the DataSet throw an error if only a `MissingTypeInfo` exists.
    
      - Getting Generic Lambdas to run with this may not be a good idea. This goes against
my original suggestion to keep this for the purpose of local development with OracleJDK, but
in hind-sight, I think things will get quite intransparent to reason about and hard to maintain/debug/fix.



> Introduce TypeHints for Java API operators
> ------------------------------------------
>
>                 Key: FLINK-1245
>                 URL: https://issues.apache.org/jira/browse/FLINK-1245
>             Project: Flink
>          Issue Type: Improvement
>          Components: Java API
>            Reporter: Timo Walther
>            Assignee: Timo Walther
>
> Due to type extraction issues with Java 8 Lambdas and many users with type erasure issues,
TypeHints need to be introduced.
> The whole discussion can be found on the mailing list:
> http://mail-archives.apache.org/mod_mbox/flink-dev/201410.mbox/%3C544FA7D6.1070708@twalthr.com%3E



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