[I] Kafka Connect: UUID columns fail to write with Parquet (ClassCastException) [iceberg]

["thswlsqls (via GitHub)" <gi...@apache.org>]

thswlsqls opened a new issue, #17076:
URL: https://github.com/apache/iceberg/issues/17076

   **Apache Iceberg version**
   main @ 49b89a8c5
   
   **Query engine**
   Kafka Connect (N/A — not Spark/Flink)
   
   **Please describe the bug**
   `RecordConverter.convertUUID()` (`kafka-connect/kafka-connect/src/main/java/org/apache/iceberg/connect/data/RecordConverter.java` line 508) converts UUID values to `byte[]` when the target file format is Parquet. The Parquet UUID writer, `ParquetValueWriters.uuids()` (via `BaseParquetWriter`'s default visitor), expects a `java.util.UUID` and converts to bytes internally, so a `byte[]` fails to cast during write. ORC (`GenericOrcWriters.uuids()`) and Avro both write `UUID` directly — only the Parquet branch in `convertUUID` diverges from this.
   
   **Steps to reproduce**
   Sink a record with a UUID field to an Iceberg table using the default file format (Parquet). `IcebergWriter.convertToRow()` calls `convertUUID()`, which returns `byte[]`; the Parquet writer stack then throws on write.
   Expected: the record writes successfully.
   Actual: `ClassCastException: class [B cannot be cast to class java.util.UUID`.
   
   **Additional context**
   The `byte[]` conversion matched the Parquet writer contract before PR #11904 ("Parquet: Add readers and writers for the internal object model", merged 2025-01-24) changed `ParquetValueWriters`' UUID writer to accept `UUID` directly. `kafka-connect` was never updated to follow, making this a regression from that writer-contract change.
   


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