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From fhueske <...@git.apache.org>
Subject [GitHub] flink pull request #3471: [FLINK-5722] [table] Add dedicated DataSetDistinct...
Date Tue, 07 Mar 2017 08:40:57 GMT
Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3471#discussion_r104613673
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/rules/dataSet/DataSetAggregateRule.scala
---
    @@ -42,6 +41,14 @@ class DataSetAggregateRule
           return false
         }
     
    +    // distinct is translated into dedicated operator
    +    if (agg.getAggCallList.isEmpty &&
    +      agg.getGroupCount == agg.getRowType.getFieldCount &&
    --- End diff --
    
    During testing I observed a case where a projection wasn't pushed down. 
    Without this check, the grouping would happen on a subset of fields and only those would
be emitted. It is not possible to change the input and output types of a ReduceFunction (which
is used to implement Distinct in a hash-combinable way), I check that the input and output
types are identical.


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