Jark Wu created FLINK-5047:
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Summary: Add tumbling group-windows for batch tables
Key: FLINK-5047
URL: https://issues.apache.org/jira/browse/FLINK-5047
Project: Flink
Issue Type: Sub-task
Reporter: Jark Wu
Add Slide group-windows for batch tables as described in
[FLIP-11](https://cwiki.apache.org/confluence/display/FLINK/FLIP-11%3A+Table+API+Stream+Aggregations).
There are two ways to implement sliding windows for batch:
1. replicate the output in order to assign keys for overlapping windows. This
is probably the more straight-forward implementation and supports any
aggregation function but blows up the data volume.
2. if the aggregation functions are combinable / pre-aggregatable, we can also
find the largest tumbling window size from which the sliding windows can be
assembled. This is basically the technique used to express sliding windows with
plain SQL (GROUP BY + OVER clauses). For a sliding window Slide(10 minutes, 2
minutes) this would mean to first compute aggregates of non-overlapping
(tumbling) 2 minute windows and assembling consecutively 5 of these into a
sliding window (could be done in a MapPartition with sorted input). The
implementation could be done as an optimizer rule to split the sliding
aggregate into a tumbling aggregate and a SQL WINDOW operator. Maybe it makes
sense to implement the WINDOW clause first and reuse this for sliding windows.
see FLINK-4692 for more discussion
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