apache/iceberg · error · IllegalArgumentException

Unsupported type:

Error message

Unsupported type: 

What it means

SparkAvroWriter.primitive switches over the Avro primitive type and only supports STRING, FIXED, BYTES (among the tail cases); any other primitive type falls to the default branch and throws IllegalArgumentException('Unsupported type: ' + primitive). It guards the Avro-to-Spark value-writer mapping.

Source

Thrown at spark/v4.0/spark/src/main/java/org/apache/iceberg/spark/data/SparkAvroWriter.java:171

            return ValueWriters.tinyints();
          } else if (type instanceof ShortType) {
            return ValueWriters.shorts();
          }
          return ValueWriters.ints();
        case LONG:
          return ValueWriters.longs();
        case FLOAT:
          return ValueWriters.floats();
        case DOUBLE:
          return ValueWriters.doubles();
        case STRING:
          return SparkValueWriters.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 Avro schema and restrict fields to supported primitive types
2. Upgrade the Iceberg version in case support was added later
3. Convert unsupported primitives to supported equivalents before writing
4. Inspect the full exception message for the offending primitive type

Example fix

// before: writing a schema with unsupported primitive
Schema schema = Schema.createUnion(...);
// after: normalize to supported primitives
Schema schema = Schema.create(Schema.Type.BYTES);

for (Schema.Field f : avroSchema.getFields()) {
  Schema.Type t = f.schema().getType();
  Preconditions.checkArgument(
      t == Schema.Type.STRING || t == Schema.Type.FIXED || t == Schema.Type.BYTES
          || /* other supported types */ true, "Unsupported type: " + t);
}

try { writer.write(row); } catch (IllegalArgumentException e) { if (e.getMessage().startsWith("Unsupported type: ")) { /* normalize schema */ } else { throw e; } }

When it happens

Trigger: Writing Spark rows to Avro whose schema contains a primitive type the writer doesn't map (e.g. unexpected/unsupported primitive in the resolved write schema).

Common situations: Schema evolution or hand-built Avro schemas with primitives outside the supported set; mismatch between the table schema and the generated Avro write schema in a custom pipeline.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Unsupported logical type:
• Unsupported logical type: {logicalType}
• Unsupported type: {primitive}
• Unsupported logical type: ${logicalType}
• Unsupported type: ${primitive}

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/e0f52be795863ffd. Report an issue: GitHub.