[FLINK-20764] BatchGroupedReduceOperator does not emit results for singleton inputs

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 1.12.0
• Fix Version/s: 1.12.1, 1.13.0
• Component/s: API / DataStream
• Labels: pull-request-available
• Assignee: Aljoscha Krettek
• Reporter: Aljoscha Krettek
• Created: 24/Dec/20 20:59
• Updated: 25/Dec/20 09:47
• Resolved: 25/Dec/20 09:47

Description

This was reported on the ML: https://lists.apache.org/thread.html/rf24ff56408d3f07a02a3726336229a5919e62c4179c9eb8361a5b76b%40%3Cuser.flink.apache.org%3E.

The problem is that the logic for setting up the "final" timer does not kick in when there is only on input.

I'll cut a PR for that and also add tests for the operator.

Issue Links

• links to: GitHub Pull Request #14489