apache/iceberg · error · java.lang.IllegalArgumentException

Unsupported Avro type '${schema.getType()}'.

Error message

Unsupported Avro type '${schema.getType()}'.

What it means

AvroSchemaConverter.convertToTypeInfo throws this when the Avro schema contains a type the converter has no mapping for when building a Flink TypeInformation (e.g. RECORD handled separately but exotic/unexpected schema kinds fall through the switch). The Avro type name is included in the message.

Source

Thrown at flink/v2.1/flink/src/main/java/org/apache/iceberg/flink/formats/avro/typeutils/AvroSchemaConverter.java:236

              || (schema.getLogicalType() != null
                  && schema.getLogicalType().getName().equals("local-timestamp-nanos"))) {
            return Types.LOCAL_DATE_TIME;
          } else if (schema.getLogicalType() == LogicalTypes.timeMicros()
              || schema.getLogicalType() == LogicalTypes.timeMillis()) {
            return Types.SQL_TIME;
          }
        }
        return Types.LONG;
      case FLOAT:
        return Types.FLOAT;
      case DOUBLE:
        return Types.DOUBLE;
      case BOOLEAN:
        return Types.BOOLEAN;
      case NULL:
        return Types.VOID;
    }
    throw new IllegalArgumentException("Unsupported Avro type '" + schema.getType() + "'.");
  }

  /**
   * Converts an Avro schema string into a nested row structure with deterministic field order and
   * data types that are compatible with Flink's Table & SQL API.
   *
   * @param avroSchemaString Avro schema definition string
   * @return data type matching the schema
   */
  public static DataType convertToDataType(String avroSchemaString) {
    return convertToDataType(avroSchemaString, true);
  }

  /**
   * Converts an Avro schema string into a nested row structure with deterministic field order and
   * data types that are compatible with Flink's Table & SQL API.
   *
   * @param avroSchemaString Avro schema definition string

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Simplify the schema to supported Avro types (record, primitives, arrays, maps, nullable unions)
2. Use convertToDataType (Table API path) which supports a broader type surface than convertToTypeInfo
3. Upgrade Iceberg/Flink to a version handling the Avro type
4. Pre-transform the schema to replace the unsupported type

Example fix

// before: unsupported union nested type
{"type":["int","long"]}
// after
{"type":"long"}

Schema s = new Schema.Parser().parse(schemaString);
Set<Schema.Type> supported = EnumSet.of(Schema.Type.RECORD, Schema.Type.ENUM, Schema.Type.ARRAY,
    Schema.Type.MAP, Schema.Type.UNION, Schema.Type.FIXED, Schema.Type.STRING, Schema.Type.BOOLEAN,
    Schema.Type.INT, Schema.Type.LONG, Schema.Type.FLOAT, Schema.Type.DOUBLE, Schema.Type.BYTES, Schema.Type.NULL);
Deque<Schema> stack = new ArrayDeque<>(List.of(s));
while (!stack.isEmpty()) {
  Schema cur = stack.pop();
  if (!supported.contains(cur.getType())) throw new IllegalStateException("Unsupported Avro type: " + cur.getType());
  cur.getFields().forEach(f -> stack.push(f.schema()));
}

try {
  TypeInformation<?> ti = AvroSchemaConverter.convertToTypeInfo(schema, false);
} catch (IllegalArgumentException e) {
  if (e.getMessage().startsWith("Unsupported Avro type")) {
    // use convertToDataType or transform the schema
  } else { throw e; }
}

When it happens

Trigger: Converting an Avro schema whose top-level or nested type is not in the handled set (e.g. unexpected schema kind like RECURSIVE sentinel or unsupported wrappers) into TypeInformation.

Common situations: Schemas with unusual constructs (unions at unsupported positions, exotic logical types) passed to the TypeInformation-based (DataSet/DataStream legacy) API; version drift between writer schema features and converter support.

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 Avro type '${schema.getType()}'.
• Unsupported Avro type '" + schema.getType() + "'.
• Unsupported type: variant
• Unsupported type:
• Unsupported type:

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/2ff4a2858e7acfb4. Report an issue: GitHub.