raminqaf opened a new pull request, #28841: URL: https://github.com/apache/flink/pull/28841
## What is the purpose of the change
VARIANT plans and executes correctly, but serializing a plan containing it
throws. `COMPILE PLAN`, `StatementSet#compilePlan` and
`TableEnvironment#compilePlanSql` are unusable with VARIANT, as is plan
restore.
Two `RelDataType` ⇄ `LogicalType` converters exist and only one knew
VARIANT. `FlinkTypeFactory`, used during planning, handles it.
`LogicalRelDataTypeConverter`, used only by plan serde, had no VARIANT handling
at all. Nothing forces the two to agree. A VARIANT-typed `RexNode`, for example
the return type of `PARSE_JSON` in a projection, failed with `Unsupported
RelDataType: VARIANT` on compile and `Logical type 'VARIANT' cannot be
converted to a RelDataType` on restore. Independently, VARIANT was missing from
`CompactSerializationChecker`, so a VARIANT in an `ExecNode` output type fell
back to generic serialization and failed with `Unable to serialize logical type
'VARIANT'`.
## Brief change log
- `LogicalRelDataTypeConverter` converts VARIANT in both directions
- `CompactSerializationChecker` reports VARIANT as compactly serializable.
This is what fixes serialization: the compact path already round-trips VARIANT
through `LogicalTypeParser`
- `LogicalTypeJsonSerializer` and `LogicalTypeJsonDeserializer` get
explicit VARIANT cases so the two switches stay symmetric and a plan that
spells VARIANT out as an object still restores
## Verifying this change
This change added tests and can be verified as follows:
- Added VARIANT to `LogicalTypeJsonSerdeTest`, `RelDataTypeJsonSerdeTest`,
`DataTypeJsonSerdeTest` and `LogicalRelDataTypeConverterTest`, standalone and
nested in `ARRAY`/`MULTISET`/`MAP`/`ROW`, nullable and `NOT NULL`
- Added a VARIANT input ref and a VARIANT-typed `ITEM` call to
`RexNodeJsonSerdeTest`
- Added the `calc-variant` restore program to `CalcRestoreTest`. Its
compiled plan carries VARIANT both as the return type of a `PARSE_JSON` call
and in the `ExecNode` output type, so it covers both reported symptoms end to
end
- Each of the five test classes fails on `master` with the errors quoted
above and passes with the fix. Reverting only the `src/main` changes makes
`calc-variant` fail at plan load, confirming the restore direction is guarded
VARIANT had zero plan serde coverage before this change.
`VariantSemanticTest` cannot catch this class of bug because `SemanticTestBase`
never serializes a plan.
## 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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Generated-by: Claude Code (Opus 5)
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