slinkydeveloper opened a new pull request #17522:
URL: https://github.com/apache/flink/pull/17522
Signed-off-by: slinkydeveloper <francescogu...@gmail.com>
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## What is the purpose of the change
The goal of this PR is to add new interfaces to reorganize the casting
throughout the Table API implementation.
The new interface called `CastRule` provides a flexible way to implement
casting logic for different input and target `LogicalType`s. `CastRule`
encapsulates the casting logic and its matching logic, which could be a match
of one or multiple input and target types, type families or a custom predicate.
A subinterface of `CastRule` called `CodeGeneratorCastRule` allows to
implement casting through code generation, in order to retain the same
performance characteristics we have in our code generator, but unifying the
code base and improving the code organization. A default implementation to
create an executable version of the casting logic is provided through janino
`ExpressionEvaluator` feature.
Having both a "callable" casting rule and a "code generating" cast rule
allows us to:
* Improve code generation codebase quality
* Reuse the same to string casting logic in `PrintUtils`
* Allow us in future to fix the constant folding for casting (see
https://issues.apache.org/jira/browse/FLINK-24588 for more details)
## Brief change log
- Introduce the new interfaces `CastRule`, `CastExecutor`,
`CodeGeneratorCastRule` and relative subinterfaces/base classes
- Provide a `CastRuleProvider` to discover cast rules
- Wired the new cast rules to the code generation
- Added a couple of rules to show how to implement them
## Verifying this change
A new test `CastRulesTest` is added to unit test the cast rules. The e2e
tests are provided by `CastFunctionITCase`.
## 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, 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? no
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