/// <summary> A search implementation allowing sorting which spans a new thread for each
        /// Searchable, waits for each search to complete and merges
        /// the results back together.
        /// </summary>
        public override TopFieldDocs Search(Weight weight, Filter filter, int nDocs, Sort sort)
        {
            // don't specify the fields - we'll wait to do this until we get results
            FieldDocSortedHitQueue hq = new FieldDocSortedHitQueue(null, nDocs);
            int totalHits             = 0;

            MultiSearcherThread[] msta = new MultiSearcherThread[searchables.Length];
            for (int i = 0; i < searchables.Length; i++)
            {
                // search each searchable
                // Assume not too many searchables and cost of creating a thread is by far inferior to a search
                msta[i] = new MultiSearcherThread(searchables[i], weight, filter, nDocs, hq, sort, i, starts, "MultiSearcher thread #" + (i + 1));
                msta[i].Start();
            }

            float maxScore = System.Single.NegativeInfinity;

            for (int i = 0; i < searchables.Length; i++)
            {
                try
                {
                    msta[i].Join();
                }
                catch (System.Threading.ThreadInterruptedException ie)
                {
                    // In 3.0 we will change this to throw
                    // InterruptedException instead
                    SupportClass.ThreadClass.Current().Interrupt();
                    throw new System.SystemException(ie.Message, ie);
                }
                System.IO.IOException ioe = msta[i].GetIOException();
                if (ioe == null)
                {
                    totalHits += msta[i].Hits();
                    maxScore   = System.Math.Max(maxScore, msta[i].GetMaxScore());
                }
                else
                {
                    // if one search produced an IOException, rethrow it
                    throw ioe;
                }
            }

            ScoreDoc[] scoreDocs = new ScoreDoc[hq.Size()];
            for (int i = hq.Size() - 1; i >= 0; i--)
            {
                // put docs in array
                scoreDocs[i] = (ScoreDoc)hq.Pop();
            }

            return(new TopFieldDocs(totalHits, scoreDocs, hq.GetFields(), maxScore));
        }
		/// <summary> A search implementation which spans a new thread for each
		/// Searchable, waits for each search to complete and merge
		/// the results back together.
		/// </summary>
		public override TopDocs Search(Weight weight, Filter filter, int nDocs)
		{
			HitQueue hq = new HitQueue(nDocs, false);
			int totalHits = 0;
			MultiSearcherThread[] msta = new MultiSearcherThread[searchables.Length];
			for (int i = 0; i < searchables.Length; i++)
			{
				// search each searchable
				// Assume not too many searchables and cost of creating a thread is by far inferior to a search
				msta[i] = new MultiSearcherThread(searchables[i], weight, filter, nDocs, hq, i, starts, "MultiSearcher thread #" + (i + 1));
				msta[i].Start();
			}
			
			for (int i = 0; i < searchables.Length; i++)
			{
				try
				{
					msta[i].Join();
				}
				catch (System.Threading.ThreadInterruptedException ie)
				{
					// In 3.0 we will change this to throw
					// InterruptedException instead
					SupportClass.ThreadClass.Current().Interrupt();
					throw new System.SystemException(ie.Message, ie);
				}
				System.IO.IOException ioe = msta[i].GetIOException();
				if (ioe == null)
				{
					totalHits += msta[i].Hits();
				}
				else
				{
					// if one search produced an IOException, rethrow it
					throw ioe;
				}
			}
			
			ScoreDoc[] scoreDocs = new ScoreDoc[hq.Size()];
			for (int i = hq.Size() - 1; i >= 0; i--)
			// put docs in array
				scoreDocs[i] = (ScoreDoc) hq.Pop();
			
			float maxScore = (totalHits == 0)?System.Single.NegativeInfinity:scoreDocs[0].score;
			
			return new TopDocs(totalHits, scoreDocs, maxScore);
		}