[jira] [Created] (FLINK-5047) Add tumbling group-windows for batch tables

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

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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