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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