matcher/localmatch.cc

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/* localmatch.cc
 *
 * 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
 * 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 "localmatch.h"

#include "autoptr.h"
#include "extraweightpostlist.h"
#include "leafpostlist.h"
#include "omdebug.h"
#include "omqueryinternal.h"
#include "queryoptimiser.h"
#include "scaleweight.h"
#include "weightinternal.h"
#include "stats.h"

#include <cfloat>
#include <cmath>
#include <map>

LocalSubMatch::LocalSubMatch(const Xapian::Database::Internal *db_,
        const Xapian::Query::Internal * query, Xapian::termcount qlen_,
        const Xapian::RSet & omrset,
        const Xapian::Weight *wt_factory_)
        : orig_query(*query), qlen(qlen_), db(db_),
          rset(db, omrset), wt_factory(wt_factory_)
{
    DEBUGCALL(MATCH, void, "LocalSubMatch::LocalSubMatch",
              db << ", " << query << ", " << qlen_ << ", " << omrset << ", " <<
              ", [wt_factory]");
}

bool
LocalSubMatch::prepare_match(bool /*nowait*/, Stats & total_stats)
{
    DEBUGCALL(MATCH, bool, "LocalSubMatch::prepare_match", "/*nowait*/");
    Stats my_stats;

    // Set the collection statistics.
    my_stats.collection_size = db->get_doccount();
    my_stats.average_length = db->get_avlength();

    // Get the term-frequencies and relevant term-frequencies.
    Xapian::TermIterator titer = orig_query.get_terms();
    Xapian::TermIterator terms_end(NULL);
    for ( ; titer != terms_end; ++titer) {
        if ((*titer).empty()) {
            my_stats.set_termfreq(*titer, db->get_doccount());
        } else {
            my_stats.set_termfreq(*titer, db->get_termfreq(*titer));
        }
        rset.will_want_reltermfreq(*titer);
    }
    rset.contribute_stats(my_stats);

    // Contribute the calculated statistics.
    total_stats += my_stats;
    RETURN(true);
}

void
LocalSubMatch::start_match(Xapian::doccount, Xapian::doccount,
                           Xapian::doccount, const Stats & total_stats)
{
    // Set the statistics for the whole collection.
    stats = &total_stats;
}

PostList *
LocalSubMatch::get_postlist_and_term_info(MultiMatch * matcher,
        map<string, Xapian::MSet::Internal::TermFreqAndWeight> * termfreqandwts)
{
    DEBUGCALL(MATCH, PostList *, "LocalSubMatch::get_postlist_and_term_info",
              matcher << ", [termfreqandwts]");

    // Build the postlist tree for the query.  This calls
    // LocalSubMatch::postlist_from_op_leaf_query() for each term in the query,
    // which builds term_info as a side effect.
    QueryOptimiser opt(*db, *this, matcher);
    PostList * pl = opt.optimise_query(&orig_query);
    if (termfreqandwts) *termfreqandwts = term_info;

    // We only need an ExtraWeightPostList if there's an extra weight
    // contribution.
    AutoPtr<Xapian::Weight> extra_wt;
    // FIXME:1.1: create the Xapian::Weight::Internal directly.
    extra_wt = wt_factory->create(stats->create_weight_internal(), qlen, 1, "");
    if (extra_wt->get_maxextra() != 0.0) {
        pl = new ExtraWeightPostList(pl, extra_wt.release(), matcher);
    }

    RETURN(pl);
}

PostList *
LocalSubMatch::postlist_from_op_leaf_query(const Xapian::Query::Internal *query,
                                           double factor)
{
    DEBUGCALL(MATCH, PostList *, "LocalSubMatch::postlist_from_op_leaf_query",
              query << ", " << factor);
    Assert(query);
    AssertEq(query->op, Xapian::Query::Internal::OP_LEAF);
    Assert(query->subqs.empty());
    bool boolean = (factor == 0.0);
    AutoPtr<Xapian::Weight> wt;
    if (!boolean) {
        // FIXME:
        // pass factor to Weight::create() - and have a shim class for classes
        // which don't understand it...
        // FIXME:1.1: create the Xapian::Weight::Internal directly.
        wt = wt_factory->create(stats->create_weight_internal(query->tname),
                                qlen, query->wqf, query->tname);
        if (fabs(factor - 1.0) > DBL_EPSILON) {
            wt = new ScaleWeight(wt.release(), factor);
        }
    }

    map<string, Xapian::MSet::Internal::TermFreqAndWeight>::iterator i;
    i = term_info.find(query->tname);
    if (i == term_info.end()) {
        Xapian::doccount tf = stats->get_termfreq(query->tname);
        Xapian::weight weight = boolean ? 0 : wt->get_maxpart();
        Xapian::MSet::Internal::TermFreqAndWeight info(tf, weight);
        term_info.insert(make_pair(query->tname, info));
    } else if (!boolean) {
        i->second.termweight += wt->get_maxpart();
    }

    LeafPostList * pl = db->open_post_list(query->tname);
    // The default for LeafPostList is to return 0 weight and maxweight which
    // is the same as boolean weighting.
    if (!boolean) pl->set_termweight(wt.release());
    RETURN(pl);
}

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