/**
* Advance the internal document iterator beyond the specified document.
*
* @param docid An internal document id.
*/
public void docIteratorAdvancePast(int docid) {
for (Qry q_i : this.args) {
q_i.docIteratorAdvancePast(docid);
}
this.docIteratorClearMatchCache();
}
@Override
protected void evaluate() throws IOException {
this.invertedList = new InvList(this.getField());
// no argument
if (args.size() == 0) return;
if (args.size() == 1) {
this.invertedList = ((QryIop) this.args.get(0)).invertedList;
return;
}
// iterate each doc, greedy algorithms
while (true) {
// init doc_id
int doc_id = Qry.INVALID_DOCID;
if (this.docIteratorHasMatchAll(null)) doc_id = this.args.get(0).docIteratorGetMatch();
// fail to find a match all
if (doc_id == Qry.INVALID_DOCID) break;
// the last argument's position in doc
List<Integer> positions = new ArrayList<Integer>();
// iterate each location
while (true) {
boolean success = false;
int position = 0;
// index from 1 to n-1
for (int i = 1; i < this.args.size(); i++) {
// get previous pos
if (!((QryIop) this.args.get(i - 1)).locIteratorHasMatch()) break;
int position1 = ((QryIop) this.args.get(i - 1)).locIteratorGetMatch();
// go beyond pre pos
((QryIop) this.args.get(i)).locIteratorAdvancePast(position1);
if (!((QryIop) this.args.get(i)).locIteratorHasMatch()) break;
int position2 = ((QryIop) this.args.get(i)).locIteratorGetMatch();
// near condition satisfied?
if (position2 > position1 && position2 - position1 <= this.dist) {
position = position2;
if (i == this.args.size() - 1) success = true;
} else {
success = false;
break;
}
}
// find a legal position
if (success) {
positions.add(position);
// move each loc pointer
for (Qry q_i : this.args) {
((QryIop) q_i).locIteratorAdvance();
}
} else {
// move first arg
((QryIop) this.args.get(0)).locIteratorAdvance();
// if no more match position for the first arg
if (!((QryIop) this.args.get(0)).locIteratorHasMatch()) break;
// reset other pointers to beginning
for (int i = 1; i < this.args.size(); i++) {
((QryIop) this.args.get(i)).locIteratorReset();
int preposition = ((QryIop) this.args.get(0)).locIteratorGetMatch();
((QryIop) this.args.get(i)).locIteratorAdvancePast(preposition);
}
}
}
// move doc pointer
for (Qry q_i : this.args) q_i.docIteratorAdvancePast(doc_id);
// success
if (positions.size() > 0) this.invertedList.appendPosting(doc_id, positions);
}
}