apache/iceberg · error · java.lang.IllegalArgumentException

Unsupported type: %s

Error message

Unsupported type: %s

What it means

FlinkAvroWriter.primitive() throws UnsupportedOperationException 'Unsupported type: <primitive>' when the Iceberg primitive type's Avro representation has no writer branch in the switch. This is a terminal catch-all meaning the Iceberg type -> Avro writer mapping cannot handle this primitive (e.g. unexpected Avro schema/type combination produced for the Iceberg type).

Source

Thrown at flink/v2.1/flink/src/main/java/org/apache/iceberg/flink/data/FlinkAvroWriter.java:175

            case SMALLINT:
              return ValueWriters.shorts();
            default:
              return ValueWriters.ints();
          }
        case LONG:
          return ValueWriters.longs();
        case FLOAT:
          return ValueWriters.floats();
        case DOUBLE:
          return ValueWriters.doubles();
        case STRING:
          return FlinkValueWriters.strings();
        case FIXED:
          return ValueWriters.fixed(primitive.getFixedSize());
        case BYTES:
          return ValueWriters.bytes();
        default:
          throw new IllegalArgumentException("Unsupported type: " + primitive);
      }
    }
  }
}

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Check the table schema for the offending primitive type from the message.
2. Upgrade iceberg-flink to a version supporting the type.
3. Avoid writing the type through the Flink Avro path (e.g. use Parquet/ORC file format via table write.format.default).
4. Reproject/drop the unsupported column before rewriting data files.

Example fix

// before
write.format.default=avro  // column type unsupported by Avro writer
// after
ALTER TABLE t SET TBLPROPERTIES ('write.format.default'='parquet');

schema.asStruct().fields().forEach(f -> {
  Preconditions.checkArgument(supportedTypeIds.contains(f.type().typeId()),
      "Type %s not supported by Flink Avro writer", f.type());
});

boolean avroWritable(Type.TypeID id) {
  switch (id) {
    case BOOLEAN: case INTEGER: case LONG: case FLOAT: case DOUBLE:
    case STRING: case BINARY: case FIXED: case DATE:
    case TIMESTAMP: case DECIMAL:
      return true;
    default:
      return false;
  }
}

try {
  writer.write(row);
} catch (UnsupportedOperationException e) {
  LOG.error("Avro writer cannot handle: {}", e.getMessage());
  throw e;
}

When it happens

Trigger: Building an Avro ValueWriter for an Iceberg primitive whose resolved Avro primitive type is not one of the handled cases (NULL, BOOLEAN, INT, LONG, FLOAT, DOUBLE, STRING, FIXED, BYTES, decimal/uuid logicals).

Common situations: Writing tables with exotic or newly added Iceberg primitive types via the Flink Avro writer; internal type resolution producing unexpected Avro 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

• Unsupported type: ${primitive}
• Unsupported Avro type '${schema.getType()}'.
• Unsupported to derive Schema for type: <logicalType>
• Avro format doesn't support non-string as key type of map. T
• Unsupported logical type: %s

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/aa76cd1eb042d6d5. Report an issue: GitHub.