manner opened a new pull request, #28991:
URL: https://github.com/apache/flink/pull/28991
## What is the purpose of the change
This pull request excludes the VARIANT data type from constant folding
VARIANT expressions. This previously resulted in a `ClassCastException` when
running a query such as the following, where a constant expression followed a
VARIANT expression in the projection.
```sql
SELECT PARSE_JSON('{}'), JSON_STRING(PARSE_JSON('{}'));
```
The `ExpressionReducer.scala` in `flink-table-planner` evaluates constant
sub-expressions, so they get computed during compile-time and not during query
run-time. It runs in two passes that must agree on which types get a slot in
the intermediate (compile-time) result:
- **Phase 1** excludes unsupported "object literal" types
(ROW/ARRAY/MAP/MULTISET/...) from compile-time evaluation. **VARIANT** was
previously missing from this list and was therefore evaluated at compile-time
and added to the intermediate result list.
- **Phase 2** has an specific case for VARIANT and treats VARIANT as
excluded from compile-time evaluation. So a VARIANT constant gets evaluated and
occupies a real slot in phase 1, but phase 2 doesn't know that and never
advances its slot index. Then the next reduced expression reads the stale slot
containing the VARIANT data and crashes on the bad cast.
## Brief change log
- Adds **VARIANT** to the exclude list of data types that use constant
folding
## Verifying this change
This change added tests and can be verified as follows:
- Added test in `JsonFunctionsITCase.java` for VARIANT, where constant
folding is enabled
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (yes / **no**)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (yes / **no**)
- The serializers: (yes / **no** / don't know)
- The runtime per-record code paths (performance sensitive): (yes / **no**
/ don't know)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes / **no** / don't
know)
- The S3 file system connector: (yes / **no** / don't know)
## Documentation
- Does this pull request introduce a new feature? (yes / **no**)
- If yes, how is the feature documented? (**not applicable** / docs /
JavaDocs / not documented)
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Generated-by: Claude Sonnet 5
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