Question

Is it possible to sort Lucene results when using a custom collector, or would I have to implement that functionality myself, in the collector object? I can’t find an overload of IndexSearcher.Search that allows me to pass in both my own collector object and a sort field.

Lucene.Net, v2.9

Answer 1

You have to implement the sort yourself. But Lucene.Net has an abstract class PriorityQueue that can be used in custom collectors (it is used internally in Lucene.Net while sorting (instead of collecting all results and then applying a sort on them) )

public class MyQueue : Lucene.Net.Util.PriorityQueue<int>
{
    public MyQueue(int MaxSize) : base()
    {
        Initialize(MaxSize);
    }

    public override bool LessThan(int a, int b)
    {
        return a < b;
    }
}

int queueSize = 3;
MyQueue pq = new MyQueue(queueSize);
pq.InsertWithOverflow(1);
pq.InsertWithOverflow(9);
pq.InsertWithOverflow(8);
pq.InsertWithOverflow(3);
pq.InsertWithOverflow(5);

int i1 = pq.Pop();
int i2 = pq.Pop();
int i3 = pq.Pop();