Index: matcher/localmatch.cc =================================================================== --- matcher/localmatch.cc (revision 7579) +++ matcher/localmatch.cc (working copy) @@ -31,6 +31,7 @@ #include "andnotpostlist.h" #include "andmaybepostlist.h" #include "filterpostlist.h" +#include "exactphrasepostlist.h" #include "phrasepostlist.h" #include "emptypostlist.h" #include "leafpostlist.h" @@ -315,6 +316,9 @@ std::vector postlists_orig = postlists; PostList *res = build_and_tree(postlists, matcher); // FIXME: handle EmptyPostList return specially? + if (query->parameter == postlists_orig.size()) { + RETURN(new ExactPhrasePostList(res, postlists_orig)); + } RETURN(new PhrasePostList(res, query->parameter, postlists_orig)); } Index: matcher/exactphrasepostlist.cc =================================================================== --- matcher/exactphrasepostlist.cc (revision 0) +++ matcher/exactphrasepostlist.cc (revision 0) @@ -0,0 +1,135 @@ +/** @file exactphrasepostlist.cc + * @brief Return docs containing terms forming a particular exact phrase. + * + * Copyright (C) 2006 Olly Betts + * + * 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 + +#include "exactphrasepostlist.h" +#include "positionlist.h" +#include "omdebug.h" + +#include +#include + +using namespace std; + +ExactPhrasePostList::ExactPhrasePostList(PostList *source_, + const vector &terms_) + : SelectPostList(source_), terms(terms_) +{ + size_t n = terms_.size(); + poslists = new PositionList*[n]; + order = new unsigned[n]; + for (size_t i = 0; i < n; ++i) order[i] = i; +} + +ExactPhrasePostList::~ExactPhrasePostList() +{ + delete [] poslists; + delete [] order; +} + +void +ExactPhrasePostList::start_position_list(unsigned i) +{ + unsigned index = order[i]; + poslists[i] = terms[index]->read_position_list(); + poslists[i]->index = index; +} + +class TermCompare { + vector & terms; + + public: + TermCompare(vector & terms_) : terms(terms_) { } + + bool operator()(unsigned a, unsigned b) const { + return terms[a]->get_wdf() < terms[b]->get_wdf(); + } +}; + +bool +ExactPhrasePostList::test_doc() +{ + DEBUGCALL(MATCH, bool, "ExactPhrasePostList::test_doc", ""); + + if (terms.size() <= 1) RETURN(true); + + // We often don't need to read all the position lists, so rather than using + // the shortest position lists first, we approximate by using the terms + // with the lowest wdf first. This will typically give the same or a very + // similar order. + sort(order, order + terms.size(), TermCompare(terms)); + + // If the first term we check only occurs too close to the start of the + // document, we only need to read one term's positions. E.g. search for + // "ripe mango" when the only occurrence of 'mango' in the current document + // is at position 0. + start_position_list(0); + poslists[0]->skip_to(poslists[0]->index); + if (poslists[0]->at_end()) RETURN(false); + + // If we get here, we'll need to read the positionlists for at least two + // terms, so check the true positionlist length for the two terms with the + // lowest wdf and if necessary swap them so the true shorter one is first. + start_position_list(1); + if (poslists[0]->get_size() < poslists[1]->get_size()) { + poslists[1]->skip_to(poslists[1]->index); + if (poslists[1]->at_end()) RETURN(false); + swap(poslists[0], poslists[1]); + } + + unsigned read_hwm = 1; + Xapian::termpos idx0 = poslists[0]->index; + do { + Xapian::termpos base = poslists[0]->get_position() - idx0; + unsigned i = 1; + while (true) { + if (i > read_hwm) { + read_hwm = i; + start_position_list(i); + // FIXME: consider comparing with poslist[0] and swapping + // if less common. Should we allow for the number of positions + // we've read from poslist[0] already? + } + Xapian::termpos required = base + poslists[i]->index; + poslists[i]->skip_to(required); + if (poslists[i]->at_end()) RETURN(false); + if (poslists[i]->get_position() != required) break; + if (++i == terms.size()) RETURN(true); + } + poslists[0]->next(); + } while (!poslists[0]->at_end()); + RETURN(false); +} + +Xapian::doccount +ExactPhrasePostList::get_termfreq_est() const +{ + // It's hard to estimate how many times the exact phrase will occur as + // it depends a lot on the phrase, but usually the exact phrase will + // occur significantly less often than the individual terms. + return source->get_termfreq_est() / 4; +} + +string +ExactPhrasePostList::get_description() const +{ + return "(ExactPhrase " + source->get_description() + ")"; +} Index: matcher/exactphrasepostlist.h =================================================================== --- matcher/exactphrasepostlist.h (revision 0) +++ matcher/exactphrasepostlist.h (revision 0) @@ -0,0 +1,62 @@ +/** @file exactphrasepostlist.h + * @brief Return docs containing terms forming a particular exact phrase. + * + * Copyright (C) 2006 Olly Betts + * + * 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_EXACTPHRASEPOSTLIST_H +#define XAPIAN_INCLUDED_EXACTPHRASEPOSTLIST_H + +#include "selectpostlist.h" +#include + +typedef Xapian::PositionIterator::Internal PositionList; + +/** Postlist which matches an exact phrase using positional information. + * + * ExactPhrasePostList only returns a posting for documents contains + * all the terms (this part is implemented using an AndPostList) and + * additionally the terms occur somewhere in the document in the order given + * and at adjacent term positions. + * + * The weight of a posting is the sum of the weights of the + * sub-postings (just like an AndPostList). + */ +class ExactPhrasePostList : public SelectPostList { + std::vector terms; + + PositionList ** poslists; + + unsigned * order; + + /// Start reading from the i-th position list. + void start_position_list(unsigned i); + + /// Test if the current document contains the terms as an exact phrase. + bool test_doc(); + + public: + ExactPhrasePostList(PostList *source_, const std::vector &terms_); + + ~ExactPhrasePostList(); + + Xapian::doccount get_termfreq_est() const; + + std::string get_description() const; +}; + +#endif Index: matcher/Makefile.am =================================================================== --- matcher/Makefile.am (revision 7579) +++ matcher/Makefile.am (working copy) @@ -6,7 +6,7 @@ andmaybepostlist.h xorpostlist.h branchpostlist.h filterpostlist.h \ phrasepostlist.h branchtermlist.h ortermlist.h selectpostlist.h \ mergepostlist.h msetpostlist.h extraweightpostlist.h remotesubmatch.h \ - localmatch.h emptysubmatch.h biaspostlist.h msetcmp.h + localmatch.h emptysubmatch.h biaspostlist.h msetcmp.h exactphrasepostlist.h noinst_LTLIBRARIES = libmatcher.la @@ -18,6 +18,7 @@ libmatcher_la_SOURCES = orpostlist.cc andpostlist.cc andnotpostlist.cc \ andmaybepostlist.cc xorpostlist.cc phrasepostlist.cc selectpostlist.cc \ + exactphrasepostlist.cc \ filterpostlist.cc ortermlist.cc expandweight.cc rset.cc \ bm25weight.cc tradweight.cc \ localmatch.cc multimatch.cc expand.cc stats.cc \