matriv opened a new pull request, #19379:
URL: https://github.com/apache/flink/pull/19379
## What is the purpose of the change
When in batch mode, the `getMonotonicity()` method of a function is
called, to determine possible optimisations. For `TRY_CAST` the
implementation needs to call `getOperandType(1)` to get the target (also
the function's return) type of the cast. This fails as for `CAST` and
`TRY_CAST` at this point we have only one operand.
`CAST` solves this in Calcite code, more specifically in
`RexCallBinding#create()` where in case the `kind` of the function is
`CAST`, a special `RexCastCallBinding` instance is created which stores
the return (target) type and returns it when `getOperandType(1)` is
called.
For `TRY_CAST` we don't have access to the stack to do something
similar, and we cannot set the kind of `TRY_CAST` to `CAST` (currently,
it's `OTHER_FUNCTION`, as this will allow the calcite stack to apply
rules and optimisations to the `TRY_CAST` call and at some point
convert it to a regular `CAST` call, thus breaking the functionality
of `TRY_CAST` (return null instead of failing).
As a solution to the problem, we simply don't implement the
`getMonotonicity()` method for `TRY_CAST`, lossing possible
optmisations.
## Brief change log
- Disable monotonicity for `TRY_CAST`
- Add tests
## Verifying this change
This change added tests and can be verified as follows:
- Added tests in `CalcITCase` which uses batch mode
- Added some additional tests to `ScalarOperatorsTest` for completeness
(these don't cover the bug fix)
## 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? **not applicable**
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