ExceptIntersectSetOperator::ExceptIntersectSetOperator(
std::vector<Table*>& input_tables, Table* output_table, bool is_all, bool is_except) :
SetOperator(input_tables, output_table, is_all), m_is_except(is_except) {
if (!is_except) {
// For intersect we want to start with the smalest table
std::vector<Table*>::iterator minTableIt =
std::min_element(m_input_tables.begin(), m_input_tables.end(), TableSizeLess());
std::swap( m_input_tables[0], *minTableIt);
}
}
bool ExceptIntersectSetOperator::processTuples()
{
// Map to keep candidate tuples. The key is the tuple itself
// The value - tuple's repeat count in the final table.
TupleMap tuples;
assert( ! m_input_tables.empty());
size_t ii = m_input_tablerefs.size();
while (ii--) {
m_input_tables[ii] = m_input_tablerefs[ii].getTable();
}
if ( ! m_is_except) {
// For intersect we want to start with the smallest table
std::vector<Table*>::iterator minTableIt =
std::min_element(m_input_tables.begin(), m_input_tables.end(), TableSizeLess());
std::swap(m_input_tables[0], *minTableIt);
}
// Collect all tuples from the first set
Table* input_table = m_input_tables[0];
collectTuples(*input_table, tuples);
//
// For each remaining input table, collect its tuple into a separate map
// and substract/intersect it from/with the first one
//
TupleMap next_tuples;
for (size_t ctr = 1, cnt = m_input_tables.size(); ctr < cnt; ctr++) {
next_tuples.clear();
input_table = m_input_tables[ctr];
assert(input_table);
collectTuples(*input_table, next_tuples);
if (m_is_except) {
exceptTupleMaps(tuples, next_tuples);
} else {
intersectTupleMaps(tuples, next_tuples);
}
}
// Insert remaining tuples to the output table
for (TupleMap::const_iterator mapIt = tuples.begin(); mapIt != tuples.end(); ++mapIt) {
TableTuple tuple = mapIt->first;
for (size_t i = 0; i < mapIt->second; ++i) {
m_output_table->insertTempTuple(tuple);
}
}
return true;
}
