Github user shaoxuan-wang commented on the issue:
https://github.com/apache/flink/pull/3993
Thanks for the review @fhueske @sunjincheng121 .
Fabian, yes, I do not think this will be a blocker for release. In fact,
this is a similar interface clean-up issue as FLINK-6457 that we want to solve.
But certainly, we can just merge this to master and include this in the next
release.
Jincheng, yes, it is one's flavor about how to implement an interface with
contracted method. From my point of view:
1. A contract method is usually to be very useful as a flag to indicate the
characteristic of an aggregator, and this information will help the optimizer
to decide the plan. Such methods are retract/merge/resetAccumulator.
2. I prefer we should just expose the user interface without any default
implementation (an interface method with default implementation will anyway not
control the user behavior). The user defined interface IMO should purely ask
users to provide minimum required methods that can let the UDX work.
3. We will call getAccumulatorType and getResultType also during the
compilation to generate the plan I think. If we put requiresOver into the
interface, we should also consider to put getAccumulatorType and getResultType
into interface as well.
Also, I think we may want to provide all the agg that requiresOver as the
built-in agg in the future. Thereby, we may not need to expose this interface
in the UDAGG at that point.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at [email protected] or file a JIRA ticket
with INFRA.
---
