Ticket #50: patch.2

Index: matcher/Makefile.mk
===================================================================
--- matcher/Makefile.mk (revision 8963)
+++ matcher/Makefile.mk (working copy)
@@ -15,6 +15,7 @@
        matcher/phrasepostlist.h\
        matcher/remotesubmatch.h\
        matcher/selectpostlist.h\
+       matcher/synonympostlist.h\
        matcher/valuerangepostlist.h\
        matcher/xorpostlist.h
 
@@ -48,6 +49,7 @@
        matcher/phrasepostlist.cc\
        matcher/rset.cc\
        matcher/selectpostlist.cc\
+       matcher/synonympostlist.cc\
        matcher/stats.cc\
        matcher/tradweight.cc\
        matcher/valuerangepostlist.cc\
Index: matcher/localmatch.cc
===================================================================
--- matcher/localmatch.cc       (revision 8957)
+++ matcher/localmatch.cc       (working copy)
@@ -3,6 +3,7 @@
  * Copyright 1999,2000,2001 BrightStation PLC
  * Copyright 2002 Ananova Ltd
  * Copyright 2002,2003,2004,2005,2006,2007 Olly Betts
+ * Copyright 2007 Lemur Consulting Ltd
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -38,6 +39,7 @@
 #include "mergepostlist.h"
 #include "extraweightpostlist.h"
 #include "valuerangepostlist.h"
+#include "synonympostlist.h"
 
 #include "omqueryinternal.h"
 
@@ -262,6 +264,26 @@
     }
 }
 
+// Convert a list of subqueries into a vector of postlists.
+void
+LocalSubMatch::postlists_from_queries(std::vector<PostList *> &result,
+                                     const Xapian::Query::Internal::subquery_list &queries,
+                                     MultiMatch * matcher, bool is_bool)
+{
+    Assert(queries.size() >= 2);
+    result.reserve(queries.size());
+
+    Xapian::Query::Internal::subquery_list::const_iterator q;
+    for (q = queries.begin(); q != queries.end(); q++) {
+       result.push_back(postlist_from_query(*q, matcher, is_bool));
+       DEBUGLINE(MATCH, "Made postlist for " << (*q)->get_description() <<
+                 ": termfreq is: (min, est, max) = (" <<
+                 result.back()->get_termfreq_min() << ", " <<
+                 result.back()->get_termfreq_est() << ", " <<
+                 result.back()->get_termfreq_max() << ")");
+    }
+}
+
 // Make a postlist from the subqueries of a query objects.
 // Operation must be either AND, OR, XOR, PHRASE, NEAR, or ELITE_SET.
 // Optimise query by building tree carefully.
@@ -270,27 +292,17 @@
        const Xapian::Query::Internal *query, MultiMatch *matcher, bool is_bool)
 {
     DEBUGCALL(MATCH, PostList *, "LocalSubMatch::postlist_from_queries", op << ", " << query << ", " << matcher << ", " << is_bool);
-    Assert(op == Xapian::Query::OP_OR || op == Xapian::Query::OP_AND ||
+    Assert(op == Xapian::Query::OP_OR ||
+          op == Xapian::Query::OP_AND ||
           op == Xapian::Query::OP_XOR ||
-          op == Xapian::Query::OP_NEAR || op == Xapian::Query::OP_PHRASE ||
+          op == Xapian::Query::OP_NEAR ||
+          op == Xapian::Query::OP_PHRASE ||
           op == Xapian::Query::OP_ELITE_SET);
-    const Xapian::Query::Internal::subquery_list &queries = query->subqs;
-    Assert(queries.size() >= 2);
 
     // Open a postlist for each query, and store these postlists in a vector.
     std::vector<PostList *> postlists;
-    postlists.reserve(queries.size());
+    postlists_from_queries(postlists, query->subqs, matcher, is_bool);
 
-    Xapian::Query::Internal::subquery_list::const_iterator q;
-    for (q = queries.begin(); q != queries.end(); q++) {
-       postlists.push_back(postlist_from_query(*q, matcher, is_bool));
-       DEBUGLINE(MATCH, "Made postlist for " << (*q)->get_description() <<
-                 ": termfreq is: (min, est, max) = (" <<
-                 postlists.back()->get_termfreq_min() << ", " <<
-                 postlists.back()->get_termfreq_est() << ", " <<
-                 postlists.back()->get_termfreq_max() << ")");
-    }
-
     // Build tree
     switch (op) {
        case Xapian::Query::OP_XOR:
@@ -427,6 +439,47 @@
            pl->set_termweight(wt);
            RETURN(pl);
        }
+       case Xapian::Query::OP_SYNONYM:
+       {
+           if (is_bool) {
+               // An or postlist returns the same documents as a synonym
+               // postlist, and doesn't pull the matches through an extra
+               // level in the postlist tree, so is more efficient than a
+               // synonym postlist if we don't care about the weights.
+               RETURN(postlist_from_queries(Xapian::Query::OP_OR, query, matcher, is_bool));
+           } else {
+               std::vector<PostList *> postlists;
+               postlists_from_queries(postlists, query->subqs, matcher, is_bool);
+               AutoPtr<SynonymPostList> res(new SynonymPostList(build_or_tree(postlists, matcher), matcher));
+
+               AutoPtr<Xapian::Weight> wt;
+
+               // FIXME - implement register_synonym.
+               //
+               // My idea is that this will generate an ID string for the
+               // synonym (perhaps get_description() will do), and then this
+               // ID can be used to get the statistics needed at search time
+               // (ie, the termfreq and the reltermfreq.
+               //
+               // The problem is that this will involve calling
+               // StatsSource.my_termfreq_is() and
+               // StatsSource.my_reltermfreq_is() with the frequencies
+               // estimated by the synonym post list, but these aren't
+               // available until the stats gatherer has come back with the
+               // overall statistics.  So, possibly, this will need to be
+               // moved to a separate later step.
+               //
+               // Also, note that we're probably going to have to prefix all
+               // the terms passed to other wt_factory->create() invocations,
+               // to distinguish real terms from virtual terms, like this one.
+
+               string tname(register_synonym(res.get()));
+               wt = wt_factory->create(&statssource, qlen, query->wqf, tname);
+
+               res->set_weight(wt.release());
+               RETURN(res.release());
+           }
+       }
        case Xapian::Query::OP_PHRASE:
        case Xapian::Query::OP_NEAR:
            // If no positional information in this sub-database, change the
Index: matcher/localmatch.h
===================================================================
--- matcher/localmatch.h        (revision 8957)
+++ matcher/localmatch.h        (working copy)
@@ -2,6 +2,7 @@
  *  @brief SubMatch class for a local database.
  */
 /* Copyright (C) 2006 Olly Betts
+ * Copyright (C) 2007 Lemur Consulting Ltd
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -76,6 +77,20 @@
     PostList * build_xor_tree(std::vector<PostList *> &postlists,
                              MultiMatch *matcher);
 
+    /** Convert a list of subqueries into a vector of postlists.
+     *
+     *  @param result  A vector which will be filled with a list of postlists, one
+     *                 for each query.
+     *  @param queries The list of queries to convert to postlists.
+     *  @param matcher The matcher to attach to each postlist.
+     *  @param is_bool Flag, if true, the postlists will be boolean.  This means
+     *                 that a BoolWeight object will be used for them.
+     */
+    void postlists_from_queries(std::vector<PostList *> &result,
+                               const Xapian::Query::Internal::subquery_list &queries,
+                               MultiMatch *matcher,
+                               bool is_bool);
+
     /** Convert the sub-queries of a Query into an optimised PostList tree.
      *
      *  We take the sub-queries from @a query, but use @op instead of
Index: matcher/synonympostlist.h
===================================================================
--- matcher/synonympostlist.h   (revision 0)
+++ matcher/synonympostlist.h   (revision 0)
@@ -0,0 +1,88 @@
+/* synonympostlist.h: Combine subqueries, weighting as if they are synonyms
+ *
+ * Copyright 2007 Lemur Consulting Ltd
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
+ */
+
+#ifndef XAPIAN_INCLUDED_SYNONYMPOSTLIST_H
+#define XAPIAN_INCLUDED_SYNONYMPOSTLIST_H
+
+#include "multimatch.h"
+#include "postlist.h"
+#include "stats.h"
+#include <vector>
+
+/** A postlist comprising several postlists SYNONYMed together.
+ *
+ *  This postlist returns all postings in the OR of the sub postlists, but
+ *  returns weights as if they represented a single term.  The term frequency
+ *  portion of the weight is approximated.
+ */
+class SynonymPostList : public PostList {
+    private:
+       /** The subtree, which starts as an OR of all the sub-postlists being
+        *  joined with Synonym, but may decay into something else.
+        */
+       PostList * subtree;
+
+       /** The object which is using this postlist to perform
+        *  a match.  This object needs to be notified when the
+        *  tree changes such that the maximum weights need to be
+        *  recalculated.
+        */
+       MultiMatch *matcher;
+
+       /** Weighting object used for calculating the synonym weights.
+        */
+       const Xapian::Weight * wt;
+
+       /** Flag indicating whether the weighting object needs the doclength.
+        */
+       bool want_doclength;
+
+    public:
+       SynonymPostList(PostList *subtree_, MultiMatch * matcher_);
+        ~SynonymPostList();
+
+       /** Set the weight object to be used for the synonym postlist.
+        *
+        *  Ownership of the weight object passes to the synonym postlist - the
+        *  caller must not delete it after use.
+        */
+       void set_weight(const Xapian::Weight * wt_);
+
+       PostList *next(Xapian::weight w_min);
+       PostList *skip_to(Xapian::docid did, Xapian::weight w_min);
+
+       Xapian::weight get_weight() const;
+       Xapian::weight get_maxweight() const;
+       Xapian::weight recalc_maxweight();
+
+       // The following methods just call through to the subtree.
+       Xapian::termcount get_wdf() const;
+       Xapian::doccount get_termfreq_min() const;
+       Xapian::doccount get_termfreq_est() const;
+       Xapian::doccount get_termfreq_max() const;
+       Xapian::docid get_docid() const;
+       Xapian::doclength get_doclength() const;
+       PositionList * read_position_list();
+       PositionList * open_position_list() const;
+       bool at_end() const;
+
+       std::string get_description() const;
+};
+
+#endif /* XAPIAN_INCLUDED_SYNONYMPOSTLIST_H */

Property changes on: matcher/synonympostlist.h
___________________________________________________________________
Name: svn:eol-style
   + native

Index: matcher/synonympostlist.cc
===================================================================
--- matcher/synonympostlist.cc  (revision 0)
+++ matcher/synonympostlist.cc  (revision 0)
@@ -0,0 +1,134 @@
+/* synonympostlist.cc: Combine subqueries, weighting as if they are synonyms
+ *
+ * Copyright 2007 Lemur Consulting Ltd
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
+ * USA
+ */
+
+#include <config.h>
+
+#include "synonympostlist.h"
+#include "branchpostlist.h"
+#include "omassert.h"
+#include "omdebug.h"
+
+SynonymPostList::SynonymPostList(PostList *subtree_,
+                                MultiMatch * matcher_)
+       : subtree(subtree_),
+         matcher(matcher_),
+         wt(NULL),
+         want_doclength(false)
+{
+}
+
+SynonymPostList::~SynonymPostList()
+{
+    delete wt;
+    delete subtree;
+}
+
+void
+SynonymPostList::set_weight(const Xapian::Weight * wt_)
+{
+    delete(wt);
+    wt = wt_;
+    want_doclength = wt_->get_sumpart_needs_doclength();
+}
+
+PostList *
+SynonymPostList::next(Xapian::weight w_min)
+{
+    DEBUGCALL(MATCH, PostList *, "SynonymPostList::next", w_min);
+    next_handling_prune(subtree, w_min, matcher);
+    RETURN(NULL);
+}
+
+PostList *
+SynonymPostList::skip_to(Xapian::docid did, Xapian::weight w_min)
+{
+    DEBUGCALL(MATCH, PostList *, "SynonymPostList::skip_to", did << ", " << w_min);
+    skip_to_handling_prune(subtree, did, w_min, matcher);
+    RETURN(NULL);
+}
+
+Xapian::weight
+SynonymPostList::get_weight() const
+{
+    return wt->get_sumpart(get_wdf(), want_doclength ? get_doclength() : 0);
+}
+
+Xapian::weight
+SynonymPostList::get_maxweight() const
+{
+    return wt->get_maxpart();
+}
+
+Xapian::weight
+SynonymPostList::recalc_maxweight()
+{
+    return SynonymPostList::get_maxweight();
+}
+
+Xapian::termcount
+SynonymPostList::get_wdf() const {
+    return subtree->get_wdf();
+}
+
+Xapian::doccount 
+SynonymPostList::get_termfreq_min() const {
+    return subtree->get_termfreq_min();
+}
+
+Xapian::doccount 
+SynonymPostList::get_termfreq_est() const {
+    return subtree->get_termfreq_est();
+}
+
+Xapian::doccount 
+SynonymPostList::get_termfreq_max() const {
+    return subtree->get_termfreq_max();
+}
+
+Xapian::docid 
+SynonymPostList::get_docid() const {
+    return subtree->get_docid();
+}
+
+Xapian::doclength 
+SynonymPostList::get_doclength() const {
+    return subtree->get_doclength();
+}
+
+PositionList * 
+SynonymPostList::read_position_list() {
+    return subtree->read_position_list();
+}
+
+PositionList * 
+SynonymPostList::open_position_list() const {
+    return subtree->open_position_list();
+}
+
+bool 
+SynonymPostList::at_end() const {
+    return subtree->at_end();
+}
+
+std::string
+SynonymPostList::get_description() const
+{
+    return "(Synonym " + subtree->get_description() + ")";
+}

Property changes on: matcher/synonympostlist.cc
___________________________________________________________________
Name: svn:eol-style
   + native

Index: tests/api_db.cc
===================================================================
--- tests/api_db.cc     (revision 8957)
+++ tests/api_db.cc     (working copy)
@@ -3,7 +3,7 @@
  * Copyright 1999,2000,2001 BrightStation PLC
  * Copyright 2002 Ananova Ltd
  * Copyright 2002,2003,2004,2005,2006,2007 Olly Betts
- * Copyright 2006 Richard Boulton
+ * Copyright 2006,2007 Lemur Consulting Ltd
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -1129,6 +1129,79 @@
     return true;
 }
 
+// Check a synonym search
+static bool test_synonym1()
+{
+    Xapian::Database db(get_database("etext"));
+    Xapian::doccount lots = 214;
+    vector<vector<Xapian::Query> > subqueries_list;
+
+    vector<Xapian::Query> subqueries;
+    subqueries.push_back(Xapian::Query("date"));
+    subqueries.push_back(Xapian::Query(Xapian::Query::OP_OR,
+                                      Xapian::Query("sky"),
+                                      Xapian::Query("glove")));
+    subqueries_list.push_back(subqueries);
+
+    subqueries.clear();
+    subqueries.push_back(Xapian::Query("sky"));
+    subqueries.push_back(Xapian::Query("date"));
+    subqueries.push_back(Xapian::Query("stein"));
+    subqueries.push_back(Xapian::Query("ally"));
+    subqueries_list.push_back(subqueries);
+
+    subqueries.clear();
+    subqueries.push_back(Xapian::Query("sky"));
+    subqueries.push_back(Xapian::Query(Xapian::Query::OP_PHRASE,
+                                      Xapian::Query("date"),
+                                      Xapian::Query("stein")));
+    subqueries_list.push_back(subqueries);
+
+    for (vector<vector<Xapian::Query> >::const_iterator
+        qlist = subqueries_list.begin();
+        qlist != subqueries_list.end(); ++qlist)
+    {
+       // Run two queries, one joining the subqueries with OR and one joining them
+       // with SYNONYM.
+       Xapian::Enquire enquire(db);
+       enquire.set_query(Xapian::Query(Xapian::Query::OP_OR, qlist->begin(), qlist->end()));
+       Xapian::MSet ormset = enquire.get_mset(0, lots);
+       Xapian::Query synquery(Xapian::Query::OP_SYNONYM, qlist->begin(), qlist->end());
+       tout << synquery << "\n";
+       enquire.set_query(synquery);
+       Xapian::MSet mset = enquire.get_mset(0, lots);
+
+       // Check that the queries return some results.
+       TEST_NOT_EQUAL(mset.size(), 0);
+       // Check that the queries return the same number of results.
+       TEST_EQUAL(mset.size(), ormset.size());
+       map<Xapian::docid, Xapian::weight> values_or;
+       map<Xapian::docid, Xapian::weight> values_synonym;
+       for (Xapian::doccount i = 0; i < mset.size(); ++i) {
+           values_or[*ormset[i]] = ormset[i].get_weight();
+           values_synonym[*mset[i]] = mset[i].get_weight();
+       }
+       TEST_EQUAL(values_or.size(), values_synonym.size());
+
+       /* Check that the weights for each item in the or mset are different from
+        * those in the synonym mset. (Note, it's technically possible that some
+        * might be equal, but unlikely, so for now we just check that none are.
+        * If this causes problems, we can change to just checking that most
+        * differ.) */
+       for (map<Xapian::docid, Xapian::weight>::const_iterator
+            j = values_or.begin();
+            j != values_or.end(); ++j)
+       {
+           Xapian::docid did = j->first;
+           // Check that all the results in the or tree make it to the synonym tree.
+           TEST(values_synonym.find(did) != values_synonym.end());
+           // Check that the weights differ.
+           TEST_NOT_EQUAL(values_or[did], values_synonym[did]);
+       }
+    }
+    return true;
+}
+
 // tests that specifying a nonexistent input file throws an exception.
 static bool test_quartzdatabaseopeningerror1()
 {
@@ -1707,6 +1780,7 @@
     // with that, and testing it there doesn't actually improve the test
     // coverage really.
     {"consistency1",      test_consistency1},
+    {"synonym1",          test_synonym1},
     // Would work with remote if we registered the weighting scheme.
     // FIXME: do this so we also test that functionality...
     {"userweight1",       test_userweight1},
@@ -1731,6 +1805,7 @@
     {"keepalive1",        test_keepalive1},
     {"termstats",         test_termstats},
     {"sortvalue1",        test_sortvalue1},
+    {"synonym1",          test_synonym1},
     {"sortrel1",          test_sortrel1},
     {"netstats1",         test_netstats1},
     {0, 0}
Index: include/xapian/query.h
===================================================================
--- include/xapian/query.h      (revision 8957)
+++ include/xapian/query.h      (working copy)
@@ -4,7 +4,7 @@
 /* Copyright 1999,2000,2001 BrightStation PLC
  * Copyright 2002 Ananova Ltd
  * Copyright 2003,2004,2005,2006,2007 Olly Betts
- * Copyright 2006 Lemur Consulting Ltd
+ * Copyright 2006,2007 Lemur Consulting Ltd
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -96,6 +96,23 @@
            /** Filter by a range test on a document value. */
            OP_VALUE_RANGE,
 
+           /** Treat a set of queries as synonyms.
+            *
+            *  This returns all results which match at least one of the
+            *  queries, but weighting as if all the sub-queries are instances
+            *  of the same term: so multiple matching terms for a document
+            *  increase the wdf value used, and the term frequency is based on
+            *  the number of documents which would match an OR of all the
+            *  subqueries.
+            *
+            *  The term frequency used will usually be an approximation,
+            *  because calculating the precise combined term frequency would
+            *  be overly expensive.
+            *
+            *  Identical to OP_OR, except for the weightings returned.
+            */
+           OP_SYNONYM,
+
            /** Select an elite set from the subqueries, and perform
             *  a query with these combined as an OR query.
             */
Index: common/remoteprotocol.h
===================================================================
--- common/remoteprotocol.h     (revision 8957)
+++ common/remoteprotocol.h     (working copy)
@@ -34,8 +34,9 @@
 // 29: Serialisation of Xapian::Error includes error_string
 // 30: Add minor protocol version numbers, to reduce need for client upgrades
 // 30.1: Pass the prefix parameter for MSG_ALLTERMS, and use it.
+// 30.2: Add synonym queries (add operator to the serialised form of queries)
 #define XAPIAN_REMOTE_PROTOCOL_MAJOR_VERSION 30
-#define XAPIAN_REMOTE_PROTOCOL_MINOR_VERSION 1
+#define XAPIAN_REMOTE_PROTOCOL_MINOR_VERSION 2
 
 /// Message types (client -> server).
 enum message_type {
Index: api/omqueryinternal.cc
===================================================================
--- api/omqueryinternal.cc      (revision 8957)
+++ api/omqueryinternal.cc      (working copy)
@@ -3,7 +3,7 @@
  * Copyright 1999,2000,2001 BrightStation PLC
  * Copyright 2002 Ananova Ltd
  * Copyright 2002,2003,2004,2005,2006,2007 Olly Betts
- * Copyright 2006 Lemur Consulting Ltd
+ * Copyright 2006,2007 Lemur Consulting Ltd
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -57,6 +57,7 @@
        case Xapian::Query::OP_PHRASE:
        case Xapian::Query::OP_ELITE_SET:
        case Xapian::Query::OP_VALUE_RANGE:
+       case Xapian::Query::OP_SYNONYM:
            return 0;
        case Xapian::Query::OP_FILTER:
        case Xapian::Query::OP_AND_MAYBE:
@@ -85,6 +86,7 @@
        case Xapian::Query::OP_NEAR:
        case Xapian::Query::OP_PHRASE:
        case Xapian::Query::OP_ELITE_SET:
+       case Xapian::Query::OP_SYNONYM:
            return UINT_MAX;
        default:
            Assert(false);
@@ -177,6 +179,9 @@
                result += str_parameter;
                result += om_tostring(parameter);
                break;
+           case Xapian::Query::OP_SYNONYM:
+               result += "=";
+               break;
        }
     }
     return result;
@@ -202,6 +207,7 @@
        case Xapian::Query::OP_PHRASE:          name = "PHRASE"; break;
        case Xapian::Query::OP_ELITE_SET:       name = "ELITE_SET"; break;
        case Xapian::Query::OP_VALUE_RANGE:     name = "VALUE_RANGE"; break;
+       case Xapian::Query::OP_SYNONYM:         name = "SYNONYM"; break;
     }
     return name;
 }
@@ -451,6 +457,8 @@
                    return new Xapian::Query::Internal(Xapian::Query::OP_VALUE_RANGE, valno,
                                                       start, stop);
                }
+               case '=':
+                   return qint_from_vector(Xapian::Query::OP_SYNONYM, subqs);
                default:
                    DEBUGLINE(UNKNOWN, "Can't parse remainder `" << p - 1 << "'");
                    throw Xapian::InvalidArgumentError("Invalid query string");
@@ -617,6 +625,7 @@
         case OP_ELITE_SET:
         case OP_OR:
         case OP_XOR:
+       case OP_SYNONYM:
             // Doing an "OR" type operation - if we've got any MatchNothing
             // subnodes, drop them; except that we mustn't become an empty
             // node due to this, so we never drop a MatchNothing subnode
@@ -690,7 +699,7 @@
                }
            }
            break;
-       case OP_OR: case OP_AND: case OP_XOR:
+       case OP_OR: case OP_AND: case OP_XOR: case OP_SYNONYM:
            // Remove duplicates if we can.
            if (subqs.size() > 1) collapse_subqs();
            break;
@@ -734,7 +743,7 @@
 void
 Xapian::Query::Internal::collapse_subqs()
 {
-    Assert(op == OP_OR || op == OP_AND || op == OP_XOR);
+    Assert(op == OP_OR || op == OP_AND || op == OP_XOR || op == OP_SYNONYM);
     typedef set<Xapian::Query::Internal *, SortPosName> subqtable;
     subqtable sqtab;
 
@@ -809,7 +818,7 @@
     Assert(!is_leaf(op));
     if (subq == 0) {
        subqs.push_back(0);
-    } else if (op == subq->op && (op == OP_AND || op == OP_OR || op == OP_XOR)) {
+    } else if (op == subq->op && (op == OP_AND || op == OP_OR || op == OP_XOR || op == OP_SYNONYM)) {
        // Distribute the subquery.
        for (subquery_list::const_iterator i = subq->subqs.begin();
             i != subq->subqs.end(); i++) {