int index = indexOrFail(fieldsRow(), key);
Map<K, E> map = new LinkedHashMap<K, E>();
for (R record : this) {
if (map.put((K) record.getValue(index), mapper.map(record)) != null) {
throw new InvalidResultException("Key " + key + " is not unique in Result for " + this);
}
}
return map;
}