bool HashJoin::next(){
// probe right side
while(rightOp->next()){
std::vector<Register*> tuple = rightOp->getOutput();
Register* attributeValue = tuple[this->regIdRight];
uint64_t hashValue = attributeValue->hash();
// if hashValue indicates a nonempty bucket of the hash table
if(!(this->hashTable.find(hashValue) == this->hashTable.end())){
// if hashValue matches any s in the bucket
vector<Register*> matchTuple = this->hashTable.at(hashValue);
Register* match = matchTuple[this->regIdLeft];
if(match == attributeValue){
// store r and s in result
vector<Register*>::iterator it;
it = result.begin();
for(unsigned i=0; i<tuple.size(); i++){
it = result.insert(it, tuple[i]);
}
for(unsigned j=0; j<matchTuple.size(); j++){
it = result.insert(it, matchTuple[j]);
}
return true;
}
}
}
return false;
}
void HashJoin::open(){
this->leftOp->open();
this->rightOp->open();
// build hashtable for the left side
while(leftOp->next()){
std::vector<Register*> tuple = leftOp->getOutput();
Register* attributeValue = tuple[this->regIdLeft];
uint64_t hashValue = attributeValue->hash();
// place tuple in hash table by hashValue
pair<uint64_t, vector<Register*>> pair (hashValue, tuple);
this->hashTable.insert(pair);
}
}
std::size_t operator()(const Register& k) const
{
return k.hash();
}