Ticket #250: patch_kan_ru_2.patch

backends/flint/flint_database.cc

@@ -5 +5 @@
  * Copyright 2002 Ananova Ltd
  * Copyright 2002,2003,2004,2005,2006,2007,2008,2009 Olly Betts
  * Copyright 2006,2008 Lemur Consulting Ltd
+ * Copyright 2009 Kan-Ru Chen
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -1241 +1242 @@
     }
 }
 
+/** Compare the positionlists for a term iterator and a termlist.
+ *
+ *  @return true if they're equal, false otherwise.
+ */
+static bool positionlists_equal(Xapian::TermIterator & termiter,
+                                FlintTermList & termlist)
+{
+    int new_count = termiter.positionlist_count();
+    int old_count = termlist.positionlist_count();
+    if (old_count != new_count)
+        return false;
+
+    PositionIterator it = termiter.positionlist_begin();
+    PositionIterator it_end = termiter.positionlist_end();
+    PositionIterator old = termlist.positionlist_begin();
+    return equal(it, it_end, old);
+}
+
 void
 FlintWritableDatabase::replace_document(Xapian::docid did,
                                         const Xapian::Document & document)
@@ -1278 +1297 @@
         }
   
         if (!modifying || document.internal->terms_modified()) {
-            // FIXME - in the case where there is overlap between the new
-            // termlist and the old termlist, it would be better to compare the
-            // two lists, and make the minimum set of modifications required.
-            // This would lead to smaller changesets for replication, and
-            // probably be faster overall.
-
-            // First, add entries to remove the postings in the underlying record.
             Xapian::Internal::RefCntPtr<const FlintWritableDatabase> ptrtothis(this);
             FlintTermList termlist(ptrtothis, did);
+            Xapian::TermIterator term = document.termlist_begin();
+            Xapian::TermIterator term_end = document.termlist_end();
+            flint_doclen_t new_doclen = termlist.get_doclength();
+            string old_tname, new_tname;
 
+            total_length -= new_doclen;
+
             termlist.next();
-            while (!termlist.at_end()) {
-                string tname = termlist.get_termname();
-                termcount wdf = termlist.get_wdf();
+            while (!termlist.at_end() || term != term_end) {
+                int cmp;
+                if (!termlist.at_end() && term != term_end) {
+                    old_tname = termlist.get_termname();
+                    new_tname = *term;
+                    cmp = old_tname.compare(new_tname);
 
-                map<string, pair<termcount_diff, termcount_diff> >::iterator i;
-                i = freq_deltas.find(tname);
-                if (i == freq_deltas.end()) {
-                    freq_deltas.insert(make_pair(tname, make_pair(-1, -termcount_diff(wdf))));
+                } else if (termlist.at_end()) {
+                    cmp = 1;
+                    new_tname = *term;
                 } else {
-                    --i->second.first;
-                    i->second.second -= wdf;
+                    cmp = -1;
+                    old_tname = termlist.get_termname();
                 }
 
-                // Remove did from tname's postlist
-                map<string, map<docid, pair<char, termcount> > >::iterator j;
-                j = mod_plists.find(tname);
-                if (j == mod_plists.end()) {
-                    map<docid, pair<char, termcount> > m;
-                    j = mod_plists.insert(make_pair(tname, m)).first;
-                }
+                if (cmp < 0) {
+                    const string& tname = old_tname;
+                    termcount wdf = termlist.get_wdf();
+                    new_doclen -= wdf;
 
-                map<docid, pair<char, termcount> >::iterator k;
-                k = j->second.find(did);
-                if (k == j->second.end()) {
-                    j->second.insert(make_pair(did, make_pair('D', 0u)));
-                } else {
-                    // Modifying a document we added/modified since the last flush.
-                    k->second = make_pair('D', 0u);
-                }
+                    map<string, pair<termcount_diff, termcount_diff> >::iterator i;
+                    i = freq_deltas.find(tname);
+                    if (i == freq_deltas.end()) {
+                        freq_deltas.insert(make_pair(tname, make_pair(-1, -termcount_diff(wdf))));
+                    } else {
+                        --i->second.first;
+                        i->second.second -= wdf;
+                    }
 
-                termlist.next();
-            }
+                    // Remove did from tname's postlist
+                    map<string, map<docid, pair<char, termcount> > >::iterator j;
+                    j = mod_plists.find(tname);
+                    if (j == mod_plists.end()) {
+                        map<docid, pair<char, termcount> > m;
+                        j = mod_plists.insert(make_pair(tname, m)).first;
+                    }
 
-            total_length -= termlist.get_doclength();
+                    map<docid, pair<char, termcount> >::iterator k;
+                    k = j->second.find(did);
+                    if (k == j->second.end()) {
+                        j->second.insert(make_pair(did, make_pair('D', 0u)));
+                    } else {
+                        // Modifying a document we added/modified since the last flush.
+                        k->second = make_pair('D', 0u);
+                    }
+                } else if (cmp != 0 || !positionlists_equal(term, termlist)) {
+                    const string& tname = new_tname;
+                    termcount wdf = term.get_wdf();
+                    new_doclen += wdf;
 
-            flint_doclen_t new_doclen = 0;
-            Xapian::TermIterator term = document.termlist_begin();
-            Xapian::TermIterator term_end = document.termlist_end();
-            for ( ; term != term_end; ++term) {
-                // Calculate the new document length
-                termcount wdf = term.get_wdf();
-                new_doclen += wdf;
+                    if (cmp > 0) {
+                        if (tname.size() > MAX_SAFE_TERM_LENGTH)
+                            throw Xapian::InvalidArgumentError("Term too long (> "STRINGIZE(MAX_SAFE_TERM_LENGTH)"): " + tname);
+                        map<string, pair<termcount_diff, termcount_diff> >::iterator i;
+                        i = freq_deltas.find(tname);
+                        if (i == freq_deltas.end()) {
+                            freq_deltas.insert(make_pair(tname, make_pair(1, termcount_diff(wdf))));
+                        } else {
+                            ++i->second.first;
+                            i->second.second += wdf;
+                        }
 
-                string tname = *term;
-                if (tname.size() > MAX_SAFE_TERM_LENGTH)
-                    throw Xapian::InvalidArgumentError("Term too long (> "STRINGIZE(MAX_SAFE_TERM_LENGTH)"): " + tname);
-                map<string, pair<termcount_diff, termcount_diff> >::iterator i;
-                i = freq_deltas.find(tname);
-                if (i == freq_deltas.end()) {
-                    freq_deltas.insert(make_pair(tname, make_pair(1, termcount_diff(wdf))));
-                } else {
-                    ++i->second.first;
-                    i->second.second += wdf;
-                }
+                        // Add did to tname's postlist
+                        map<string, map<docid, pair<char, termcount> > >::iterator j;
+                        j = mod_plists.find(tname);
+                        if (j == mod_plists.end()) {
+                            map<docid, pair<char, termcount> > m;
+                            j = mod_plists.insert(make_pair(tname, m)).first;
+                        }
+                        map<docid, pair<char, termcount> >::iterator k;
+                        k = j->second.find(did);
+                        if (k != j->second.end()) {
+                            Assert(k->second.first == 'D');
+                            k->second.first = 'M';
+                            k->second.second = wdf;
+                        } else {
+                            j->second.insert(make_pair(did, make_pair('A', wdf)));
+                        }
+                    }
 
-                // Add did to tname's postlist
-                map<string, map<docid, pair<char, termcount> > >::iterator j;
-                j = mod_plists.find(tname);
-                if (j == mod_plists.end()) {
-                    map<docid, pair<char, termcount> > m;
-                    j = mod_plists.insert(make_pair(tname, m)).first;
+                    PositionIterator it = term.positionlist_begin();
+                    PositionIterator it_end = term.positionlist_end();
+                    if (it != it_end) {
+                        position_table.set_positionlist(
+                                                        did, tname, it, it_end);
+                    } else {
+                        position_table.delete_positionlist(did, tname);
+                    }
                 }
-                map<docid, pair<char, termcount> >::iterator k;
-                k = j->second.find(did);
-                if (k != j->second.end()) {
-                    Assert(k->second.first == 'D');
-                    k->second.first = 'M';
-                    k->second.second = wdf;
-                } else {
-                    j->second.insert(make_pair(did, make_pair('A', wdf)));
+                if (termlist.at_end())
+                    ++term;
+                else if (term == term_end)
+                    termlist.next();
+                else {
+                    if (cmp >= 0)
+                        ++term;
+                    if (cmp <= 0)
+                        termlist.next();
                 }
+            }
 
-                PositionIterator it = term.positionlist_begin();
-                PositionIterator it_end = term.positionlist_end();
-                if (it != it_end) {
-                    position_table.set_positionlist(
-                        did, tname, it, it_end);
-                } else {
-                    position_table.delete_positionlist(did, tname);
-                }
-            }
             LOGLINE(DB, "Calculated doclen for replacement document " << did << " as " << new_doclen);
 
             // Set the termlist