presto-main/src/main/java/io/prestosql/operator/index/FieldSetFilteringRecordSet.java/FieldSetFilteringRecordCursor/FieldSetFilteringRecordCursor
class FieldSetFilteringRecordCursor:        private FieldSetFilteringRecordCursor(RecordCursor delegate, List<Set<Field>> fieldSets)
        {
            this.delegate = delegate;
            this.fieldSets = fieldSets;
        }