[FLINK-2991] Extend Window Operators to Allow Efficient Fold Operation

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.0.0
• Component/s: API / DataStream
• Assignee: Aljoscha Krettek
• Reporter: Aljoscha Krettek
• Created: 10/Nov/15 09:38
• Updated: 28/Feb/19 11:14
• Resolved: 12/Feb/16 17:56

Description

Right now, a window fold is implemented as a WindowFunction that gets all the elements as input. No pre-aggregation is performed. The window operator should be extended to also allow the fold to also be pre-aggregated.

This requires changing the signature of the WindowBuffer so that it can emit a type other than the input type.