[FLINK-3254] CombineFunction interface not respected

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 0.10.1, 1.0.0
• Fix Version/s: 1.0.0
• Component/s: API / DataSet
• Assignee: Kostas Kloudas
• Reporter: Fabian Hueske
• Created: 18/Jan/16 15:04
• Updated: 03/Feb/16 23:30
• Resolved: 03/Feb/16 23:30

Description

The DataSet API offers a CombineFunction interface, which differs from the GroupCombineFunction interface by being restricted to return a single value instead of returning arbitrary many values through a Collector.
The JavaDocs of the GroupCombineFunction point to the CombineFunction interface, advertising it as more efficient.

However, the CombineFunction interface is nor respected by Flink, i.e., a GroupReduceFunction that implements this interface is executed without leveraging the combine method.