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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3943) Add support for EXCEPT (set minus)
Date Wed, 29 Jun 2016 23:13:55 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3943?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15355947#comment-15355947
] 

ASF GitHub Bot commented on FLINK-3943:
---------------------------------------

Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2169#discussion_r69044111
  
    --- Diff: docs/apis/table.md ---
    @@ -536,6 +536,29 @@ Table result = left.unionAll(right);
         </tr>
     
         <tr>
    +      <td><strong>Minus</strong></td>
    +      <td>
    +        <p>Similar to a SQL EXCEPT clause. Returns elements from the first table
that do not exist in the second table. Both tables must have identical schema, i.e., field
names and types.</p>
    --- End diff --
    
    Please rephrase to "Except returns records from the first table that do not exist in the
second table. Records that exist multiple times in the first table are returned exactly once,
i.e., duplicates are removed.".


> Add support for EXCEPT (set minus)
> ----------------------------------
>
>                 Key: FLINK-3943
>                 URL: https://issues.apache.org/jira/browse/FLINK-3943
>             Project: Flink
>          Issue Type: New Feature
>          Components: Table API & SQL
>    Affects Versions: 1.1.0
>            Reporter: Fabian Hueske
>            Assignee: Ivan Mushketyk
>            Priority: Minor
>
> Currently, the Table API and SQL do not support EXCEPT.
> EXCEPT can be executed as a coGroup on all fields that forwards records of the first
input if the second input is empty.
> In order to add support for EXCEPT to the Table API and SQL we need to:
> - Implement a {{DataSetMinus}} class that translates an EXCEPT into a DataSet API program
using a coGroup on all fields.
> - Implement a {{DataSetMinusRule}} that translates a Calcite {{LogicalMinus}} into a
{{DataSetMinus}}.
> - Extend the Table API (and validation phase) to provide an except() method.



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