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https://issues.apache.org/jira/browse/FLINK-4557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15869407#comment-15869407
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Fabian Hueske commented on FLINK-4557:
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Hi [~sunjincheng121], I think your last two comment should go into FLINK-5803
and FLINK-5804, right?
Can you move them and delete them here? Thanks, Fabian
> 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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