cvsimport

[beagle.git] / beagled / LuceneQueryingDriver.cs

//
// LuceneQueryingDriver.cs
//
// Copyright (C) 2004-2005 Novell, Inc.
//

//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//

using System;
using System.Collections;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Text;
using System.Threading;
using System.Xml;
using System.Xml.Serialization;

using Lucene.Net.Analysis;
using Lucene.Net.Analysis.Standard;
using Lucene.Net.Documents;
using Lucene.Net.Index;
using Lucene.Net.QueryParsers;
using LNS = Lucene.Net.Search;

using Beagle.Util;

namespace Beagle.Daemon {

        public class LuceneQueryingDriver : LuceneCommon {

                static public bool Debug = false;

                public delegate bool UriFilter (Uri uri);
                public delegate double RelevancyMultiplier (Hit hit);

                public LuceneQueryingDriver (string index_name, int minor_version, bool read_only) 
                        : base (index_name, minor_version)
                {
                        // FIXME: Maybe the LuceneQueryingDriver should never try to create the index?
                        if (Exists ())
                                Open (read_only);
                        else if (!read_only)
                                Create ();
                        else {
                                // We're in read-only mode, but we can't create an index.
                                // Maybe a different exception would be better?  This one is caught
                                // in QueryDriver.LoadStaticQueryable ()
                                throw new InvalidOperationException ();
                        }

                        // Initialize the user text cache only if we're not in
                        // read-only mode.  StaticQueryables instantiate their
                        // own text caches that are stored in a separate
                        // location.
                        if (!read_only)
                                text_cache = TextCache.UserCache;
                }

                ////////////////////////////////////////////////////////////////


                ////////////////////////////////////////////////////////////////

                public Uri[] PropertyQuery (Property prop)
                {
                        // FIXME: Should we support scanning the secondary
                        // index as well?

                        IndexReader primary_reader;
                        LNS.IndexSearcher primary_searcher;

                        primary_reader = LuceneCommon.GetReader (PrimaryStore);
                        primary_searcher = new LNS.IndexSearcher (primary_reader);

                        Term term = new Term (PropertyToFieldName (prop.Type, prop.Key), prop.Value);
                        LNS.TermQuery query = new LNS.TermQuery (term);
                        LNS.Hits hits = primary_searcher.Search (query);

                        Uri[] uri_list = new Uri [hits.Length ()];
                        for (int i = 0; i < hits.Length (); i++) {
                                Document doc;
                                doc = hits.Doc (i);
                                uri_list [i] = GetUriFromDocument (doc);
                        }

                        primary_searcher.Close ();
                        ReleaseReader (primary_reader);

                        return uri_list;
                }

                ////////////////////////////////////////////////////////////////

                // Returns the lowest matching score before the results are
                // truncated.
                public void DoQuery (Query               query,
                                     IQueryResult        result,
                                     ICollection         search_subset_uris, // should be internal uris
                                     UriFilter           uri_filter,
                                     HitFilter           hit_filter)
                {
                        if (Debug)
                                Logger.Log.Debug ("###### {0}: Starting low-level queries", IndexName);

                        Stopwatch sw;
                        sw = new Stopwatch ();
                        sw.Start ();

                        // Assemble all of the parts into a bunch of Lucene queries

                        ArrayList primary_required_part_queries = null;
                        ArrayList secondary_required_part_queries = null;

                        LNS.BooleanQuery primary_prohibited_part_query = null;
                        LNS.BooleanQuery secondary_prohibited_part_query = null;

                        AndHitFilter all_hit_filters;
                        all_hit_filters = new AndHitFilter ();
                        if (hit_filter != null)
                                all_hit_filters.Add (hit_filter);

                        ArrayList term_list = new ArrayList ();

                        foreach (QueryPart part in query.Parts) {
                                LNS.Query primary_part_query;
                                LNS.Query secondary_part_query;
                                HitFilter part_hit_filter;
                                QueryPartToQuery (part,
                                                  false, // we want both primary and secondary queries
                                                  part.Logic == QueryPartLogic.Required ? term_list : null,
                                                  out primary_part_query,
                                                  out secondary_part_query,
                                                  out part_hit_filter);

                                if (primary_part_query == null)
                                        continue;

                                switch (part.Logic) {
                                        
                                case QueryPartLogic.Required:
                                        if (primary_required_part_queries == null) {
                                                primary_required_part_queries = new ArrayList ();
                                                secondary_required_part_queries = new ArrayList ();
                                        }
                                        primary_required_part_queries.Add (primary_part_query);
                                        secondary_required_part_queries.Add (secondary_part_query);
                                        
                                        if (part_hit_filter != null)
                                                all_hit_filters.Add (part_hit_filter);
                                        
                                        break;

                                case QueryPartLogic.Prohibited:
                                        if (primary_prohibited_part_query == null)
                                                primary_prohibited_part_query = new LNS.BooleanQuery ();
                                        primary_prohibited_part_query.Add (primary_part_query, false, false);

                                        if (secondary_part_query != null) {
                                                if (secondary_prohibited_part_query == null)
                                                        secondary_prohibited_part_query = new LNS.BooleanQuery ();
                                                secondary_prohibited_part_query.Add (secondary_part_query, false, false);
                                        }

                                        if (part_hit_filter != null) {
                                                NotHitFilter nhf;
                                                nhf = new NotHitFilter (part_hit_filter);
                                                all_hit_filters.Add (new HitFilter (nhf.HitFilter));
                                        }

                                        break;
                                }
                        }

                        // If we have no required parts, give up.
                        if (primary_required_part_queries == null)
                                return;
                        
                        //
                        // Now that we have all of these nice queries, let's execute them!
                        //

                        // Create the searchers that we will need.

                        IndexReader primary_reader;
                        LNS.IndexSearcher primary_searcher;
                        IndexReader secondary_reader = null;
                        LNS.IndexSearcher secondary_searcher = null;

                        primary_reader = LuceneCommon.GetReader (PrimaryStore);
                        primary_searcher = new LNS.IndexSearcher (primary_reader);

                        if (SecondaryStore != null) {
                                secondary_reader = LuceneCommon.GetReader (SecondaryStore);
                                if (secondary_reader.NumDocs () == 0) {
                                        ReleaseReader (secondary_reader);
                                        secondary_reader = null;
                                }
                        }

                        if (secondary_reader != null)
                                secondary_searcher = new LNS.IndexSearcher (secondary_reader);


                        // Possibly create our whitelists from the search subset.
                        
                        LuceneBitArray primary_whitelist = null;
                        LuceneBitArray secondary_whitelist = null;
                        
                        if (search_subset_uris != null && search_subset_uris.Count > 0) {
                                primary_whitelist = new LuceneBitArray (primary_searcher);
                                if (secondary_searcher != null)
                                        secondary_whitelist = new LuceneBitArray (secondary_searcher);

                                foreach (Uri uri in search_subset_uris) {
                                        primary_whitelist.AddUri (uri);
                                        if (secondary_whitelist != null)
                                                secondary_whitelist.AddUri (uri);
                                }
                                primary_whitelist.FlushUris ();
                                if (secondary_whitelist != null)
                                        secondary_whitelist.FlushUris ();
                        }


                        // Build blacklists from our prohibited parts.
                        
                        LuceneBitArray primary_blacklist = null;
                        LuceneBitArray secondary_blacklist = null;

                        if (primary_prohibited_part_query != null) {
                                primary_blacklist = new LuceneBitArray (primary_searcher,
                                                                        primary_prohibited_part_query);
                                
                                if (secondary_searcher != null) {
                                        secondary_blacklist = new LuceneBitArray (secondary_searcher);
                                        if (secondary_prohibited_part_query != null)
                                                secondary_blacklist.Or (secondary_prohibited_part_query);
                                        primary_blacklist.Join (secondary_blacklist);
                                }
                        }

                        
                        // Combine our whitelist and blacklist into just a whitelist.
                        
                        if (primary_blacklist != null) {
                                if (primary_whitelist == null) {
                                        primary_blacklist.Not ();
                                        primary_whitelist = primary_blacklist;
                                } else {
                                        primary_whitelist.AndNot (primary_blacklist);
                                }
                        }

                        if (secondary_blacklist != null) {
                                if (secondary_whitelist == null) {
                                        secondary_blacklist.Not ();
                                        secondary_whitelist = secondary_blacklist;
                                } else {
                                        secondary_whitelist.AndNot (secondary_blacklist);
                                }
                        }

                        BetterBitArray primary_matches = null;

                        if (primary_required_part_queries != null) {

                                if (secondary_searcher != null)
                                        primary_matches = DoRequiredQueries_TwoIndex (primary_searcher,
                                                                                      secondary_searcher,
                                                                                      primary_required_part_queries,
                                                                                      secondary_required_part_queries,
                                                                                      primary_whitelist,
                                                                                      secondary_whitelist);
                                else
                                        primary_matches = DoRequiredQueries (primary_searcher,
                                                                             primary_required_part_queries,
                                                                             primary_whitelist);

                        } 

                        sw.Stop ();
                        if (Debug)
                                Logger.Log.Debug ("###### {0}: Finished low-level queries in {1}", IndexName, sw);
                        sw.Reset ();
                        sw.Start ();

                        // Only generate results if we got some matches
                        if (primary_matches != null && primary_matches.ContainsTrue ()) {
                                GenerateQueryResults (primary_reader,
                                                      primary_searcher,
                                                      secondary_searcher,
                                                      primary_matches,
                                                      result,
                                                      term_list,
                                                      query.MaxHits,
                                                      uri_filter,
                                                      new HitFilter (all_hit_filters.HitFilter),
                                                      IndexName);
                        }

                        //
                        // Finally, we clean up after ourselves.
                        //
                        
                        primary_searcher.Close ();
                        if (secondary_searcher != null)
                                secondary_searcher.Close ();
                        ReleaseReader (primary_reader);
                        if (secondary_reader != null)
                                ReleaseReader (secondary_reader);


                        sw.Stop ();
                        if (Debug)
                                Logger.Log.Debug ("###### {0}: Processed query in {1}", IndexName, sw);

                }

                ////////////////////////////////////////////////////////////////

                //
                // Special logic for handling our set of required queries
                //

                // This is the easy case: we just combine all of the queries
                // into one big BooleanQuery.
                private static BetterBitArray DoRequiredQueries (LNS.IndexSearcher primary_searcher,
                                                                 ArrayList primary_queries,
                                                                 BetterBitArray primary_whitelist)
                {
                        LNS.BooleanQuery combined_query;
                        combined_query = new LNS.BooleanQuery ();
                        foreach (LNS.Query query in primary_queries)
                                combined_query.Add (query, true, false);

                        LuceneBitArray matches;
                        matches = new LuceneBitArray (primary_searcher, combined_query);
                        if (primary_whitelist != null)
                                matches.And (primary_whitelist);

                        return matches;
                }

                // This code attempts to execute N required queries in the
                // most efficient order to minimize the amount of time spent
                // joining between the two indexes.  It returns a joined bit
                // array of matches against the primary index.

                private class MatchInfo : IComparable {

                        public LuceneBitArray PrimaryMatches = null;
                        public LuceneBitArray SecondaryMatches = null;
                        public int UpperBound = 0;

                        public void Join ()
                        {
                                PrimaryMatches.Join (SecondaryMatches);
                        }

                        public void RestrictBy (MatchInfo joined)
                        {
                                if (joined != null) {
                                        this.PrimaryMatches.And (joined.PrimaryMatches);
                                        this.SecondaryMatches.And (joined.SecondaryMatches);
                                }

                                UpperBound = 0;
                                UpperBound += PrimaryMatches.TrueCount;
                                UpperBound += SecondaryMatches.TrueCount;
                        }

                        public int CompareTo (object obj)
                        {
                                MatchInfo other = (MatchInfo) obj;
                                return this.UpperBound - other.UpperBound;
                        }
                }

                // Any whitelists that are passed in must be fully joined, or
                // query results will be incorrect.
                private static BetterBitArray DoRequiredQueries_TwoIndex (LNS.IndexSearcher primary_searcher,
                                                                          LNS.IndexSearcher secondary_searcher,
                                                                          ArrayList primary_queries,
                                                                          ArrayList secondary_queries,
                                                                          BetterBitArray primary_whitelist,
                                                                          BetterBitArray secondary_whitelist)
                {
                        ArrayList match_info_list;
                        match_info_list = new ArrayList ();

                        // First, do all of the low-level queries
                        // and store them in our MatchInfo 
                        for (int i = 0; i < primary_queries.Count; ++i) {
                                LNS.Query pq, sq;
                                pq = primary_queries [i] as LNS.Query;
                                sq = secondary_queries [i] as LNS.Query;

                                LuceneBitArray p_matches = null, s_matches = null;
                                p_matches = new LuceneBitArray (primary_searcher);
                                if (pq != null) {
                                        p_matches.Or (pq);
                                        if (primary_whitelist != null)
                                                p_matches.And (primary_whitelist);
                                }

                                s_matches = new LuceneBitArray (secondary_searcher);
                                if (sq != null) {
                                        s_matches.Or (sq);
                                        if (secondary_whitelist != null)
                                                s_matches.And (secondary_whitelist);
                                }

                                MatchInfo info;
                                info = new MatchInfo ();
                                info.PrimaryMatches = p_matches;
                                info.SecondaryMatches = s_matches;
                                info.RestrictBy (null); // a hack to initialize the UpperBound
                                match_info_list.Add (info);
                        }

                        // We want to be smart about the order we do this in,
                        // to minimize the expense of the Join.
                        while (match_info_list.Count > 1) {

                                // linear scan to find the minimum
                                int index_min = 0;
                                for (int i = 1; i < match_info_list.Count; ++i)
                                        if (((MatchInfo) match_info_list [i]).CompareTo ((MatchInfo) match_info_list [index_min]) < 0)
                                                index_min = i;

                                MatchInfo smallest;
                                smallest = match_info_list [index_min] as MatchInfo;
                                match_info_list.RemoveAt (index_min);

                                // We can short-circuit if our smallest set of
                                // matches is empty.
                                if (smallest.UpperBound == 0)
                                        return smallest.PrimaryMatches; // this must be an empty array.

                                smallest.Join ();

                                foreach (MatchInfo info in match_info_list)
                                        info.RestrictBy (smallest);
                        }
                        
                        // For the final pair, we don't need to do a full join:
                        // mapping the secondary onto the primary is sufficient
                        MatchInfo last;
                        last = match_info_list [0] as MatchInfo;
                        last.SecondaryMatches.ProjectOnto (last.PrimaryMatches);

                        return last.PrimaryMatches;
                }               

                ////////////////////////////////////////////////////////////////

                static private void ScoreHits (Hashtable   hits_by_id,
                                               IndexReader reader,
                                               ICollection term_list)
                {
                        Stopwatch sw;
                        sw = new Stopwatch ();
                        sw.Start ();

                        LNS.Similarity similarity;
                        similarity = LNS.Similarity.GetDefault ();

                        foreach (Term term in term_list) {

                                double idf;
                                idf = similarity.Ldf (reader.DocFreq (term), reader.MaxDoc ());

                                int hit_count;
                                hit_count = hits_by_id.Count;

                                TermDocs term_docs;
                                term_docs = reader.TermDocs (term);
                                while (term_docs.Next () && hit_count > 0) {
                                        
                                        int id;
                                        id = term_docs.Doc ();

                                        Hit hit;
                                        hit = hits_by_id [id] as Hit;
                                        if (hit != null) {
                                                double tf;
                                                tf = similarity.Tf (term_docs.Freq ());
                                                hit.Score += tf * idf;
                                                --hit_count;
                                        }
                                }
                        }

                        sw.Stop ();
                }

                ////////////////////////////////////////////////////////////////

                // Lame iterator methods because we use two different ones
                // depending on which algorithm we use.
                private static IEnumerable IterateMatches (BetterBitArray primary_matches)
                {
                        int j = primary_matches.Count;

                        // Walk across the matches backwards, since newer
                        // documents are more likely to be at the end of
                        // the index.
                        while (true) {
                                int i = primary_matches.GetPreviousTrueIndex (j);
                                if (i < 0)
                                        yield break;
                                j = i-1; // This way we can't forget to adjust i

                                yield return i;
                        }
                }

                private static IEnumerable IterateOrderedMatches (int[] ordered_matches)
                {
                        int i;

                        for (i = 0; i < ordered_matches.Length; i++)
                                yield return ordered_matches [i];
                }

                private class DocAndId {
                        public Document Doc;
                        public int Id;
                }

                //
                // Given a set of hits, broadcast some set out as our query
                // results.
                //

                private static void GenerateQueryResults (IndexReader       primary_reader,
                                                          LNS.IndexSearcher primary_searcher,
                                                          LNS.IndexSearcher secondary_searcher,
                                                          BetterBitArray    primary_matches,
                                                          IQueryResult      result,
                                                          ICollection       query_term_list,
                                                          int               max_results,
                                                          UriFilter         uri_filter,
                                                          HitFilter         hit_filter,
                                                          string            index_name)
                {
                        TopScores top_docs = null;
                        ArrayList all_docs = null;

                        if (Debug)
                                Logger.Log.Debug (">>> {0}: Initially handed {1} matches", index_name, primary_matches.TrueCount);

                        if (primary_matches.TrueCount <= max_results) {
                                if (Debug)
                                        Logger.Log.Debug (">>> {0}: Initial count is within our limit of {1}", index_name, max_results);
                                all_docs = new ArrayList ();
                        } else {
                                if (Debug)
                                        Logger.Log.Debug (">>> {0}: Number of hits is capped at {1}", index_name, max_results);
                                top_docs = new TopScores (max_results);
                        }

                        Stopwatch total, a, b, c, d;
                        total = new Stopwatch ();
                        a = null;
                        b = new Stopwatch ();
                        c = new Stopwatch ();
                        d = new Stopwatch ();

                        total.Start ();

                        // There are two ways we can determine the max_results
                        // most recent items:  
                        //
                        // One is to instantiate Lucene documents for each of
                        // the document IDs in primary_matches.  This is a
                        // fairly expensive operation.
                        //
                        // The other is to walk through the list of all
                        // document IDs in descending time order.  This is
                        // a less expensive operation, but adds up over time
                        // on large data sets.
                        //
                        // We can walk about 2.5 docs for every Document we
                        // instantiate.  So what we'll do, if we have more
                        // matches than available hits, is walk (m * 1.25)
                        // docs to see if we can fill out the top 100 hits.
                        // If not, we'll fall back to creating documents
                        // for all of them.

                        int[] ordered_matches = null;
                        if (primary_matches.TrueCount > max_results) {
                                a = new Stopwatch ();
                                a.Start ();

                                TermDocs docs = primary_reader.TermDocs ();
                                TermEnum enumerator = primary_reader.Terms (new Term ("InvertedTimestamp", ""));
                                ordered_matches = new int [max_results];
                                int docs_found = 0;
                                int docs_walked = 0;
                                int max_docs = (int) (primary_matches.TrueCount * 1.25);

                                do {
                                        Term term = enumerator.Term ();
                                
                                        if (term.Field () != "InvertedTimestamp")
                                                break;

                                        docs.Seek (enumerator);

                                        while (docs.Next ()
                                               && docs_found < ordered_matches.Length
                                               && docs_walked < max_docs) {
                                                int doc_id = docs.Doc ();

                                                if (primary_matches.Get (doc_id)) {
                                                        ordered_matches [docs_found] = docs.Doc ();
                                                        docs_found++;
                                                }
                                
                                                docs_walked++;
                                        }
                                } while (enumerator.Next ()
                                         && docs_found < ordered_matches.Length
                                         && docs_walked < max_docs);

                                docs.Close ();

                                // We've found all the docs we can return in a subset!
                                // Fantastic, we've probably short circuited a slow search.
                                if (docs_found == max_results) {
                                        all_docs = new ArrayList ();
                                        top_docs = null;
                                } else {
                                        // Bad luck! Not all docs found
                                        // Start afresh - this time traversing all results
                                        ordered_matches = null;
                                }

                                a.Stop ();
                                if (Debug) {
                                        Log.Debug (">>> {0}: Walked {1} items, populated an enum with {2} items", index_name, docs_walked, docs_found, a);
                                        
                                        if (docs_found == max_results)
                                                Log.Debug (">>> {0}: Successfully short circuited timestamp ordering!", index_name);
                                }
                        }

                        b.Start ();
                        
                        int count = 0;
                        IEnumerable enumerable;

                        if (ordered_matches != null) {
                                enumerable = IterateOrderedMatches (ordered_matches);
                       } else
                                enumerable = IterateMatches (primary_matches);

                        foreach (int i in enumerable) {
                                count++;

                                Document doc;
                                doc = primary_searcher.Doc (i);

                                // Check the timestamp --- if we have already reached our
                                // limit, we might be able to reject it immediately.
                                string timestamp_str;
                                long timestamp_num = 0;

                                timestamp_str = doc.Get ("Timestamp");
                                if (timestamp_str == null) {
                                        Logger.Log.Warn ("No timestamp on {0}!", GetUriFromDocument (doc));
                                } else {
                                        timestamp_num = Int64.Parse (doc.Get ("Timestamp"));
                                        if (top_docs != null && ! top_docs.WillAccept (timestamp_num))
                                                continue;
                                }

                                // If we have a UriFilter, apply it.
                                if (uri_filter != null) {
                                        Uri uri;
                                        uri = GetUriFromDocument (doc);
                                        if (! uri_filter (uri)) 
                                                continue;
                                }

                                DocAndId doc_and_id = new DocAndId ();
                                doc_and_id.Doc = doc;
                                doc_and_id.Id = i;

                                // Add the document to the appropriate data structure.
                                // We use the timestamp_num as the score, so high
                                // scores correspond to more-recent timestamps.
                                if (all_docs != null)
                                        all_docs.Add (doc_and_id);
                                else
                                        top_docs.Add (timestamp_num, doc_and_id);
                        }

                        if (Debug)
                                Log.Debug (">>> {0}: Processed roughly {1} documents", index_name, count);

                        b.Stop ();

                        c.Start ();

                        ICollection final_list_of_docs;
                        if (all_docs != null)
                                final_list_of_docs = all_docs;
                        else
                                final_list_of_docs = top_docs.TopScoringObjects;

                        ArrayList final_list_of_hits;
                        final_list_of_hits = new ArrayList (final_list_of_docs.Count);

                        // This is used only for scoring
                        Hashtable hits_by_id = null;
                        hits_by_id = new Hashtable ();

                        // If we aren't using the secondary index, the next step is
                        // very straightforward.
                        if (secondary_searcher == null) {

                                foreach (DocAndId doc_and_id in final_list_of_docs) {
                                        Hit hit;
                                        hit = DocumentToHit (doc_and_id.Doc);
                                        hits_by_id [doc_and_id.Id] = hit;
                                        final_list_of_hits.Add (hit);
                                }

                        } else {

                                if (Debug)
                                        Logger.Log.Debug (">>> {0}: Performing cross-index Hit reunification", index_name);

                                Hashtable hits_by_uri;
                                hits_by_uri = UriFu.NewHashtable ();

                                LuceneBitArray secondary_matches;
                                secondary_matches = new LuceneBitArray (secondary_searcher);

                                foreach (DocAndId doc_and_id in final_list_of_docs) {
                                        Hit hit;
                                        hit = DocumentToHit (doc_and_id.Doc);
                                        hits_by_id [doc_and_id.Id] = hit;
                                        hits_by_uri [hit.Uri] = hit;
                                        secondary_matches.AddUri (hit.Uri);
                                }

                                secondary_matches.FlushUris ();
                                
                                // Attach all of our secondary properties
                                // to the hits
                                int j = 0;
                                while (true) {
                                        int i = secondary_matches.GetNextTrueIndex (j);
                                        if (i >= secondary_matches.Count)
                                                break;
                                        j = i+1;

                                        Document secondary_doc;
                                        secondary_doc = secondary_searcher.Doc (i);
                                        
                                        Uri uri;
                                        uri = GetUriFromDocument (secondary_doc);

                                        Hit hit;
                                        hit = hits_by_uri [uri] as Hit;

                                        AddPropertiesToHit (hit, secondary_doc, false);

                                        final_list_of_hits.Add (hit);
                                }
                        }

                        ScoreHits (hits_by_id, primary_reader, query_term_list);

                        c.Stop ();

                        // If we used the TopScores object, we got our original
                        // list of documents sorted for us.  If not, sort the
                        // final list.
                        if (top_docs == null)
                                final_list_of_hits.Sort ();

                        d.Start ();

                        // If we have a hit_filter, use it now.
                        if (hit_filter != null) {
                                for (int i = 0; i < final_list_of_hits.Count; ++i) {
                                        Hit hit;
                                        hit = final_list_of_hits [i] as Hit;
                                        if (! hit_filter (hit)) {
                                                if (Debug)
                                                        Logger.Log.Debug ("Filtered out {0}", hit.Uri);
                                                final_list_of_hits [i] = null;
                                        }
                                }
                        }

                        // Before we broadcast a hit, we strip out any
                        // properties in the PrivateNamespace.  We
                        // manipulate the property ArrayList directory,
                        // which is pretty gross... but this is safe,
                        // since removing items will not change the sort
                        // order.
                        foreach (Hit hit in final_list_of_hits) {
                                if (hit == null)
                                        continue;
                                int i = 0;
                                while (i < hit.Properties.Count) {
                                        Property prop = hit.Properties [i] as Property;
                                        if (prop.Key.StartsWith (Property.PrivateNamespace))
                                                hit.Properties.RemoveAt (i);
                                        else
                                                ++i;
                                }
                        }

                        result.Add (final_list_of_hits, primary_matches.TrueCount);

                        d.Stop ();
                        total.Stop ();

                        if (Debug) {
                                Logger.Log.Debug (">>> {0}: GenerateQueryResults time statistics:", index_name);
                                Logger.Log.Debug (">>> {0}: Short circuit {1,6} ({2:0.0}%)", index_name, a == null ? "N/A" : a.ToString (), a == null ? 0.0 : 100 * a.ElapsedTime / total.ElapsedTime);
                                Logger.Log.Debug (">>> {0}:    First pass {1,6} ({2:0.0}%)", index_name, b, 100 * b.ElapsedTime / total.ElapsedTime);
                                Logger.Log.Debug (">>> {0}:  Hit assembly {1,6} ({2:0.0}%)", index_name, c, 100 * c.ElapsedTime / total.ElapsedTime);
                                Logger.Log.Debug (">>> {0}:    Final pass {1,6} ({2:0.0}%)", index_name, d, 100 * d.ElapsedTime / total.ElapsedTime);
                                Logger.Log.Debug (">>> {0}:         TOTAL {1,6}", index_name, total);
                        }
                }

        }
}