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

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

Timo Walther created FLINK-4557:
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             Summary: 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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