twalthr opened a new pull request #14714:
URL: https://github.com/apache/flink/pull/14714
## What is the purpose of the change
```
/**
* Example for implementing more complex {@link UserDefinedFunction}s.
*
* <p>In many use cases, function signatures can be reflectively extracted
from a UDF class. The
* annotations {@link DataTypeHint} and {@link FunctionHint} help if
reflective information is not
* enough and needs to be enriched with further logical details. Check the
website documentation as
* well as the docs of {@link ScalarFunction}, {@link TableFunction}, and
{@link AggregateFunction}
* for more information.
*
* <p>Both reflective extraction and annotations are suitable for function
signatures with fixed
* input and output types. However, for advanced use cases it might be
required to derive an output
* type from one of the argument types or perform stricter validation.
*
* <p>This example demonstrates various UDF implementations. We are
executing multiple Flink jobs
* where the result is written to stdout.
*/
```
## Brief change log
- `LastDatedValueFunction` aggregate function added
- `InternalRowMergerFunction` function added
## Verifying this change
This change added tests and can be verified as follows:
`AdvancedFunctionsExampleITCase`
## 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)`: no
- The serializers: no
- The runtime per-record code paths (performance sensitive): no
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: no
- The S3 file system connector: no
## Documentation
- Does this pull request introduce a new feature? no
- If yes, how is the feature documented? JavaDocs
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