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  1. Flink
  2. FLINK-4557 Table API Stream Aggregations
  3. FLINK-5658

Add event time OVER ROWS BETWEEN UNBOUNDED PRECEDING aggregation to SQL

    Details

    • Type: Sub-task
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 1.3.0
    • Component/s: Table API & SQL
    • Labels:
      None

      Description

      The goal of this issue is to add support for OVER RANGE aggregations on event time streams to the SQL interface.

      Queries similar to the following should be supported:

      SELECT 
        a, 
        SUM(b) OVER (PARTITION BY c ORDER BY rowTime() ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS sumB,
        MIN(b) OVER (PARTITION BY c ORDER BY rowTime() ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS minB
      FROM myStream
      

      The following restrictions should initially apply:

      • All OVER clauses in the same SELECT clause must be exactly the same.
      • The PARTITION BY clause is optional (no partitioning results in single threaded execution).
      • The ORDER BY clause may only have rowTime() as parameter. rowTime() is a parameterless scalar function that just indicates processing time mode.
      • bounded PRECEDING is not supported (see FLINK-5655)
      • FOLLOWING is not supported.

      The restrictions will be resolved in follow up issues. If we find that some of the restrictions are trivial to address, we can add the functionality in this issue as well.

      An event-time OVER ROWS window will not be able to handle late data, because this would mean in insert a row into a sorted order shift all other computations. This would be too expensive to maintain. Therefore, we will throw an error if a user tries to use an event-time OVER ROWS window with late data handling.

      This issue includes:

      • Design of the DataStream operator to compute OVER ROW aggregates
      • Translation from Calcite's RelNode representation (LogicalProject with RexOver expression).

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              • Assignee:
                Yuhong_kyo hongyuhong
                Reporter:
                fhueske Fabian Hueske
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                • Created:
                  Updated:
                  Resolved: