apache/iceberg · error · IllegalArgumentException

Unsupported type:

Error message

Unsupported type: 

What it means

PlannedDataReader.primitive() switches over Avro primitive types and throws this IllegalArgumentException in the default branch when the read schema contains a primitive type with no mapping (e.g. an unhandled type such as a record-level mismatch or an exotic primitive). It's the read-side counterpart of DataWriter's unsupported-type error.

Source

Thrown at core/src/main/java/org/apache/iceberg/data/avro/PlannedDataReader.java:203

          return ValueReaders.ints();
        case LONG:
          return ValueReaders.longs();
        case FLOAT:
          if (partner != null && partner.typeId() == Type.TypeID.DOUBLE) {
            return ValueReaders.floatsAsDoubles();
          }
          return ValueReaders.floats();
        case DOUBLE:
          return ValueReaders.doubles();
        case STRING:
          // might want to use a binary-backed container like Utf8
          return ValueReaders.strings();
        case FIXED:
          return ValueReaders.fixed(primitive.getFixedSize());
        case BYTES:
          return ValueReaders.byteBuffers();
        default:
          throw new IllegalArgumentException("Unsupported type: " + primitive);
      }
    }
  }
}

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Identify the unsupported primitive from the message and align the read schema with supported types.
2. Upgrade Iceberg so PlannedDataReader supports the type.
3. Project the schema to exclude the unsupported field before reading.
4. Add a ValueReaders mapping case if the type should be supported.

Example fix

// before
reader.read(schemaWithUnsupportedPrimitive, decoder); // throws
// after
Schema projected = schema.select("supportedField");
reader.read(projected, decoder);

for (Schema.Field f : schema.getFields()) {
  Schema.Type t = f.schema().getType();
  if (!Set.of("NULL","BOOLEAN","INT","LONG","FLOAT","DOUBLE","STRING","FIXED","BYTES", "RECORD","ARRAY","MAP","UNION").contains(t.name())) {
    throw new IllegalArgumentException("Unsupported primitive: " + t);
  }
}

null

try { return reader.read(schema, decoder); } catch (IllegalArgumentException e) { if (e.getMessage().startsWith("Unsupported type")) { return reader.read(projectSupported(schema), decoder); } throw e; }

When it happens

Trigger: Calling PlannedDataReader.read on a schema whose primitive branch falls through the switch — the schema's primitive type is not one of NULL/BOOLEAN/INT/LONG/FLOAT/DOUBLE/STRING/FIXED/BYTES handled above.

Common situations: Reading data written with newer Avro/Iceberg types by an older reader; corrupted or hand-built schemas; version skew between writer and reader libraries.

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: variant
• Unsupported type:
• Unknown logical type:
• Unsupported Avro type '${schema.getType()}'.
• Unsupported Avro type '${schema.getType()}'.

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/0d5c669975c28213. Report an issue: GitHub.