[jira] [Commented] (FLINK-4557) Table API Stream Aggregations

["shijinkui (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-4557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15500099#comment-15500099 ] 

shijinkui commented on FLINK-4557:
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Does this plan started? 
What's the progress now?

thanks

> Table API Stream Aggregations
> -----------------------------
>
>                 Key: FLINK-4557
>                 URL: https://issues.apache.org/jira/browse/FLINK-4557
>             Project: Flink
>          Issue Type: New Feature
>          Components: Table API & SQL
>            Reporter: Timo Walther
>
> The Table API is a declarative API to define queries on static and streaming tables. So far, only projection, selection, and union are supported operations on streaming tables.
> This issue and the corresponding FLIP proposes to add support for different types of aggregations on top of streaming tables. In particular, we seek to support:
> *Group-window aggregates*, i.e., aggregates which are computed for a group of elements. A (time or row-count) window is required to bound the infinite input stream into a finite group.
> *Row-window aggregates*, i.e., aggregates which are computed for each row, based on a window (range) of preceding and succeeding rows.
> Each type of aggregate shall be supported on keyed/grouped or non-keyed/grouped data streams for streaming tables as well as batch tables.
> Since time-windowed aggregates will be the first operation that require the definition of time, we also need to discuss how the Table API handles time characteristics, timestamps, and watermarks.
> The FLIP can be found here: 
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-11%3A+Table+API+Stream+Aggregations



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