[jira] [Created] (FLINK-1664) Fix sorting on POJO fields

["Fabian Hueske (JIRA)" <ji...@apache.org>]

Fabian Hueske created FLINK-1664:
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             Summary: Fix sorting on POJO fields
                 Key: FLINK-1664
                 URL: https://issues.apache.org/jira/browse/FLINK-1664
             Project: Flink
          Issue Type: Bug
          Components: JobManager
    Affects Versions: 0.8.0, 0.9
            Reporter: Fabian Hueske


Flink's groupSort, partitionSort, and outputSort operators allow to sort partitions or groups of a DataSet.

If the sort is defined on a POJO field, the sort order is not well defined. Internally, the POJO is recursively decomposed into atomic fields (primitives or generic types) and sorted by sorting these atomic fields. Thereby, the order of these atomic fields is not well defined (I believe it is lexicographic order of the POJO's member names).

IMO, the best approach is to forbid sorting on POJO types for now. Instead, it is always possible to select the nested fields of the POJO that should be used for sorting. Later we can relax this restriction.




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