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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-5655) Add event time OVER RANGE BETWEEN x PRECEDING aggregation to SQL
Date Wed, 29 Mar 2017 08:19:41 GMT

    [ https://issues.apache.org/jira/browse/FLINK-5655?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15946719#comment-15946719
] 

ASF GitHub Bot commented on FLINK-5655:
---------------------------------------

Github user fhueske commented on the issue:

    https://github.com/apache/flink/pull/3629
  
    The problem with the state clean-up is that we always keep some state for each key. If
the keys of the stream are moving (i.e., there is not a fixed set of keys) then the size of
the state will grow infinitely. 
    
    So we should add a configuration option that defines when the state of a key can be cleaned,
i.e., a min and max duration how long we keep the state of a key without any updates. This
should be similar to the RocksDB TTL, but I would like to have this not only for RocksDB but
for all backends by registering timers that clear the state. 
    
    I don't think we have to add this for this PR but should address this issue before the
1.3 release.


> Add event time OVER RANGE BETWEEN x PRECEDING aggregation to SQL
> ----------------------------------------------------------------
>
>                 Key: FLINK-5655
>                 URL: https://issues.apache.org/jira/browse/FLINK-5655
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Table API & SQL
>            Reporter: Fabian Hueske
>            Assignee: sunjincheng
>
> 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:
> {code}
> SELECT 
>   a, 
>   SUM(b) OVER (PARTITION BY c ORDER BY rowTime() RANGE BETWEEN INTERVAL '1' HOUR PRECEDING
AND CURRENT ROW) AS sumB,
>   MIN(b) OVER (PARTITION BY c ORDER BY rowTime() RANGE BETWEEN INTERVAL '1' HOUR PRECEDING
AND CURRENT ROW) AS minB
> FROM myStream
> {code}
> 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.
> - UNBOUNDED PRECEDING is not supported (see FLINK-5658)
> - 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.
> 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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