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From "sunjincheng (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-5990) Add event time OVER ROWS BETWEEN x PRECEDING aggregation to SQL
Date Tue, 21 Mar 2017 04:13:42 GMT

    [ https://issues.apache.org/jira/browse/FLINK-5990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15934068#comment-15934068
] 

sunjincheng commented on FLINK-5990:
------------------------------------

In this JIRA. I'll definition two concepts: 
1. out-of-order
2. late-event 

For above two concepts, we need add a configuration: 
1. allowedLateness: which use can definition.the value of the allowedLateness is length of
time that the user configures the allowable data delay.

Determine whether the out-of-order or late-event is based on the value of allowedLateness
e.g.:
** allowedLateness = 2 **
InputData:
```
(1L, 1, "Hello"),
(2L, 2, "Hello"),
(4L, 4, "Hello"),
(3L, 3, "Hello"),
(7L, 7, "Hello"),
(7L, 8, "Hello"),
(5L, 5, "Hello"),
(8L, 8, "Hello World"),
(20L, 20, "Hello World"),
(9L, 9, "Hello World"))

`(3L, 3, "Hello")` is out-of-order, Because 4-3=1 < 2
`(9L, 9, "Hello World")` is late-event,Because 20-9=11>2
What do you think ?  @fhueske 

> Add event time OVER ROWS BETWEEN x PRECEDING aggregation to SQL
> ---------------------------------------------------------------
>
>                 Key: FLINK-5990
>                 URL: https://issues.apache.org/jira/browse/FLINK-5990
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Table API & SQL
>            Reporter: sunjincheng
>            Assignee: sunjincheng
>
> The goal of this issue is to add support for OVER ROWS 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() ROWS BETWEEN 2 PRECEDING AND CURRENT
ROW) AS sumB,
>   MIN(b) OVER (PARTITION BY c ORDER BY rowTime() ROWS BETWEEN 2 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 event 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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