apache/cassandra · error · InvalidRequestException

Duplicate field name

Error message

Duplicate field name '%s' in type '%s'

What it means

CreateTypeStatement.apply validation: the same field name appears more than once in the UDT's field list (detected via a HashSet of FieldIdentifier); duplicate field names are not permitted in a user-defined type.

Solutions

1. Rename or remove duplicate fields so each field name in the type is unique.

When it happens

Trigger: Thrown at src/java/org/apache/cassandra/cql3/statements/schema/CreateTypeStatement.java:107 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/05f2ef3ad80b829a. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/cql3/statements/schema/CreateTypeStatement.java:107

    {
        Keyspaces schema = metadata.schema.getKeyspaces();
        KeyspaceMetadata keyspace = schema.getNullable(keyspaceName);
        if (null == keyspace)
            throw ire("Keyspace '%s' doesn't exist", keyspaceName);

        UserType existingType = keyspace.types.getNullable(bytes(typeName));
        if (null != existingType)
        {
            if (ifNotExists)
                return schema;

            throw ire("A user type with name '%s' already exists", typeName);
        }

        Set<FieldIdentifier> usedNames = new HashSet<>();
        for (FieldIdentifier name : fieldNames)
            if (!usedNames.add(name))
                throw ire("Duplicate field name '%s' in type '%s'", name, typeName);

        for (CQL3Type.Raw type : rawFieldTypes)
        {
            if (type.isCounter())
                throw ire("A user type cannot contain counters");

            if (type.isUDT() && !type.isFrozen())
                throw ire("A user type cannot contain non-frozen UDTs");
        }

        List<AbstractType<?>> fieldTypes =
            rawFieldTypes.stream()
                         .map(t -> t.prepare(keyspaceName, keyspace.types).getType())
                         .collect(toList());

        UserType udt = new UserType(keyspaceName, bytes(typeName), fieldNames, fieldTypes, true);
        return schema.withAddedOrUpdated(keyspace.withSwapped(keyspace.types.with(udt)));
    }

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