[jira] [Commented] (FLINK-1599) TypeComperator with no keys and comparators matches some elements

["Maximilian Michels (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-1599?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14939994#comment-14939994 ] 

Maximilian Michels commented on FLINK-1599:
-------------------------------------------

The driver implementations assume that at least one key is extracted and that the number of keys matches the number of comparators. This just needs to be updated in the JavaDoc of {{TypeComperator}}.

> TypeComperator with no keys and comparators matches some elements
> -----------------------------------------------------------------
>
>                 Key: FLINK-1599
>                 URL: https://issues.apache.org/jira/browse/FLINK-1599
>             Project: Flink
>          Issue Type: Bug
>          Components: Distributed Runtime
>    Affects Versions: 0.8.0
>            Reporter: Maximilian Michels
>            Priority: Minor
>
> If you create a custom type comparator by subclassing {{TypeComperator}} and implement {{int extractKeys(Object record, Object[] target, int index)}} and {{TypeComparator[] getFlatComparators()}} to return 0 and no type comparators respectively, the {{coGroup}} operator (possibly others) find matching elements although no comparators have been specified.
> In this case, the expected behavior for a CoGroup would be that only elements from one side are supplied in the CoGroup method.



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