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https://issues.apache.org/jira/browse/FLINK-8124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16266099#comment-16266099
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ASF GitHub Bot commented on FLINK-8124:
---------------------------------------
GitHub user casidiablo opened a pull request:
https://github.com/apache/flink/pull/5073
[FLINK-8124] Make Trigger implementations more generic
# What is the purpose of the change
Flink provides implementations of the `Trigger<T, W extend Window>` class
that are unnecessarily
specific. `EventTimeTrigger`, for instance, extends `Trigger<Object,
TimeWindow>`.
Since most window assigners provided also implement `WindowAssigner<Object,
TimeWindow>` this
is usually not a problem. However, when implementing custom
`WindowAssigner` it could be problematic:
```java
public class CustomWindowAssigner extends WindowAssigner<SomePojo,
AnotherWindowImpl> {
...
@Override
public Trigger<SomePojo, AnotherWindowImpl>
getDefaultTrigger(StreamExecutionEnvironment env) {
return EventTimeTrigger.create(); // compiler complains about
typing
}
...
}
```
## Brief change log
This commit makes `Trigger` implementations generic, keeping them
compatible with the current
windowing implementations as well as custom ones.
- `EventTimeTrigger<T, W extends Window>`
- `ProcessingTimeTrigger<T, W extends Window>`
- `ContinuousEventTimeTrigger<T, W extends Window>`
- `ContinuousProcessingTimeTrigger<T, W extends Window>`
- `CountTrigger<T, W extends Window>`
## Verifying this change
This change is already covered by existing tests, such as
`WindowTranslationTest` or `DataStreamTest`.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): no
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: yes
- The serializers: no
- The runtime per-record code paths (performance sensitive): no
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Yarn/Mesos, ZooKeeper: no
- The S3 file system connector: no
## Documentation
- Does this pull request introduce a new feature? no
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/casidiablo/flink generic-triggers
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/5073.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #5073
----
commit 12abf2d9b7c8d68991aad4e05683744bc3ed7a33
Author: Cristian <[email protected]>
Date: 2017-11-26T14:50:44Z
[FLINK-8124] Make Trigger implementations more generic
Flink provides implementations of the `Trigger<T, W extend Window>` class
that are unnecessarily
specific. `EventTimeTrigger`, for instance, extends `Trigger<Object,
TimeWindow>`.
Since most window assigners provided also implement `WindowAssigner<Object,
TimeWindow>` this
is usually not a problem. However, when implementing custom
`WindowAssigner` it could be problematic:
```java
public class CustomWindowAssigner extends WindowAssigner<SomePojo,
AnotherWindowImpl> {
...
@Override
public Trigger<SomePojo, AnotherWindowImpl>
getDefaultTrigger(StreamExecutionEnvironment env) {
return EventTimeTrigger.create(); // compiler complains about
typing
}
...
}
```
This commit makes `Trigger` implementations generic, keeping them
compatible with the current
windowing implementations as well as custom ones.
----
> EventTimeTrigger (and other triggers) could have less specific generic types
> ----------------------------------------------------------------------------
>
> Key: FLINK-8124
> URL: https://issues.apache.org/jira/browse/FLINK-8124
> Project: Flink
> Issue Type: Improvement
> Components: Core
> Reporter: Cristian
> Priority: Minor
>
> When implementing custom WindowAssigners, it is possible to need different
> implementations of the {{Window}} class (other than {{TimeWindow}}). In such
> cases, it is not possible to use the existing triggers (e.g.
> {{EventTimeTrigger}}) because it extends from {{Trigger<Object, TimeWindow>}}
> which is (unnecessarily?) specific.
> It should be possible to make that class more generic by using
> {{EventTimeTrigger<T, W extends Window> extends Trigger<T, W>}} instead.
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