// for debugging - may be unused
void SetOperator::printTupleMap(const char* nonce, TupleMap &tuples) {
    printf("Printing TupleMap (%s): ", nonce);
    for (TupleMap::const_iterator mapIt = tuples.begin(); mapIt != tuples.end(); ++mapIt) {
        TableTuple tuple = mapIt->first;
        printf("%s, ", tuple.debugNoHeader().c_str());
    }
    printf("\n");
    fflush(stdout);
}