in java/avro-converter/src/main/java/com/microsoft/azure/schemaregistry/kafka/connect/avro/AvroConverterUtils.java [1368:1373]
private static String unionMemberFieldName(Schema schema, int index) {
if (schema.type() == Schema.Type.STRUCT || isEnumSchema(schema) || isFixedSchema(schema)) {
return splitName(schema.name())[1];
}
return CONNECT_TYPES_TO_AVRO_TYPES.get(schema.type()).getName();
}