What causes "Unsupported type: %s" in apache/iceberg?

Identify the offending physical type from the message and rewrite the files with standard types (e.g. INT64 millis timestamps).

apache/iceberg · error · java.lang.UnsupportedOperationException

Unsupported type: %s

Error message

Unsupported type: %s

What it means

FlinkParquetReaders.primitive() throws UnsupportedOperationException 'Unsupported type: <primitive>' when a Parquet primitive column has no reader branch — the physical Parquet type cannot be decoded into the expected Iceberg/Flink value (terminal catch-all in the reader builder).

Source

Thrown at flink/v2.1/flink/src/main/java/org/apache/iceberg/flink/data/FlinkParquetReaders.java:342

          return new ParquetValueReaders.ByteArrayReader(desc);
        case INT32:
          if (expected.typeId() == org.apache.iceberg.types.Type.TypeID.LONG) {
            return new ParquetValueReaders.IntAsLongReader(desc);
          } else {
            return new ParquetValueReaders.UnboxedReader<>(desc);
          }
        case FLOAT:
          if (expected.typeId() == org.apache.iceberg.types.Type.TypeID.DOUBLE) {
            return new ParquetValueReaders.FloatAsDoubleReader(desc);
          } else {
            return new ParquetValueReaders.UnboxedReader<>(desc);
          }
        case BOOLEAN:
        case INT64:
        case DOUBLE:
          return new ParquetValueReaders.UnboxedReader<>(desc);
        default:
          throw new UnsupportedOperationException("Unsupported type: " + primitive);
      }
    }
  }

  private static class BinaryDecimalReader
      extends ParquetValueReaders.PrimitiveReader<DecimalData> {
    private final int precision;
    private final int scale;

    BinaryDecimalReader(ColumnDescriptor desc, int precision, int scale) {
      super(desc);
      this.precision = precision;
      this.scale = scale;
    }

    @Override
    public DecimalData read(DecimalData ignored) {
      Binary binary = column.nextBinary();

View on GitHub (pinned to 86d9c8fc54)

Solutions

Identify the offending physical type from the message and rewrite the files with standard types (e.g. INT64 millis timestamps).
Re-write files with `rewrite_data_files` to normalize physical encodings.
Exclude/projection-drop the problematic column while reading.
Upgrade iceberg-flink if the type gained reader support.

Example fix

// before
// column written as INT96 timestamp
// after
// rewrite parquet with INT64 (TIMESTAMP_MICROS) and read again

Defensive patterns

Strategy: validation

Validate before calling

// inspect physical parquet types before reading
ParquetFileReader pfr = ParquetFileReader.open(conf, path);
MessageType schema = pfr.getFooter().getFileMetaData().getSchema();
schema.getFields().forEach(f -> LOG.info("parquet field: {} {}", f.getName(), f.asPrimitiveType()));

Try / catch

try (CloseableIterable<RowData> rows = reader.read()) {
  rows.forEach(out::collect);
} catch (UnsupportedOperationException e) {
  if (e.getMessage().startsWith("Unsupported type")) {
    throw new IOException("Unsupported Parquet physical type: " + e.getMessage(), e);
  }
  throw e;
}

Prevention

Avoid INT96 and nonstandard physical types when producing Parquet externally.
Rewrite files with iceberg rewrite actions after format changes.
Check physical types with parquet-tools before registering external files.

When it happens

Trigger: Reading Parquet files whose physical column type for an Iceberg primitive is not among the handled cases (e.g. unexpected INT96 or an unsupported FIXED_LEN_BYTE_ARRAY usage).

Common situations: Parquet files written by external tools with nonstandard physical types; parquet-avro INT96 timestamps; schema evolution leaving old physical types.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/ba70aa4709cf3686. Report an issue: GitHub.