weightinternal.h

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/* Copyright (C) 2007 Lemur Consulting Ltd
 * Copyright (C) 2009,2010,2011,2013,2014,2015,2020 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_WEIGHTINTERNAL_H
#define XAPIAN_INCLUDED_WEIGHTINTERNAL_H

#include "xapian/weight.h"

#include "xapian/database.h"
#include "xapian/query.h"

#include "backends/database.h"
#include "internaltypes.h"
#include "omassert.h"

#include <algorithm>
#include <map>
#include <string>

struct TermFreqs {
    Xapian::doccount termfreq = 0;
    Xapian::doccount reltermfreq = 0;
    Xapian::termcount collfreq = 0;

    double max_part = 0.0;

    TermFreqs() {}
    TermFreqs(Xapian::doccount termfreq_,
              Xapian::doccount reltermfreq_,
              Xapian::termcount collfreq_,
              double max_part_ = 0.0)
        : termfreq(termfreq_),
          reltermfreq(reltermfreq_),
          collfreq(collfreq_),
          max_part(max_part_) {}

    void operator+=(const TermFreqs & other) {
        termfreq += other.termfreq;
        reltermfreq += other.reltermfreq;
        collfreq += other.collfreq;
        // max_part shouldn't be set yet.
        Assert(max_part == 0.0);
        Assert(other.max_part == 0.0);
    }

    std::string get_description() const;
};

namespace Xapian {

class RSet;

class Weight::Internal {
#ifdef XAPIAN_ASSERTIONS

    size_t subdbs = 0;

    mutable bool finalised = false;
#endif

  public:
    Xapian::totallength total_length = 0;

    Xapian::doccount collection_size = 0;

    Xapian::doccount rset_size = 0;

    bool have_max_part = false;

    Xapian::Database db;

    Xapian::Query query;

    std::map<std::string, TermFreqs> termfreqs;

    Internal() { }

    Internal & operator+=(const Internal & inc);

    void merge(const Weight::Internal& o);

    void set_query(const Xapian::Query &query_) {
        AssertEq(subdbs, 0);
        query = query_;
    }

    void accumulate_stats(const Xapian::Database::Internal &sub_db,
                          const Xapian::RSet &rset);

    bool get_stats(const std::string & term,
                   Xapian::doccount & termfreq,
                   Xapian::doccount & reltermfreq,
                   Xapian::termcount & collfreq) const {
#ifdef XAPIAN_ASSERTIONS
        finalised = true;
#endif
        // We pass an empty std::string for term when calculating the extra
        // weight.
        if (term.empty()) {
            termfreq = collection_size;
            collfreq = collection_size;
            reltermfreq = rset_size;
            return true;
        }

        auto i = termfreqs.find(term);
        if (i == termfreqs.end()) {
            termfreq = reltermfreq = collfreq = 0;
            return false;
        }

        termfreq = i->second.termfreq;
        reltermfreq = i->second.reltermfreq;
        collfreq = i->second.collfreq;
        return true;
    }

    bool get_stats(const std::string & term,
                   Xapian::doccount & termfreq) const {
        Xapian::doccount dummy1;
        Xapian::termcount dummy2;
        return get_stats(term, termfreq, dummy1, dummy2);
    }

    bool get_termweight(const std::string & term, double & termweight) const {
#ifdef XAPIAN_ASSERTIONS
        finalised = true;
#endif
        termweight = 0.0;
        if (term.empty()) {
            return false;
        }

        auto i = termfreqs.find(term);
        if (i == termfreqs.end()) {
            return false;
        }

        termweight = i->second.max_part;
        return true;
    }

    void get_max_termweight(double & min_tw, double & max_tw) {
        auto i = termfreqs.begin();
        while (i != termfreqs.end() && i->second.max_part == 0.0) ++i;
        if (rare(i == termfreqs.end())) {
            min_tw = max_tw = 0.0;
            return;
        }
        min_tw = max_tw = i->second.max_part;
        while (++i != termfreqs.end()) {
            double max_part = i->second.max_part;
            if (max_part > max_tw) {
                max_tw = max_part;
            } else if (max_part < min_tw && max_part != 0.0) {
                min_tw = max_part;
            }
        }
    }

    void set_max_part(const std::string & term, double max_part) {
        Assert(!term.empty());
        auto i = termfreqs.find(term);
        if (i != termfreqs.end()) {
            have_max_part = true;
            double& val = i->second.max_part;
            val = std::max(val, max_part);
        }
    }

    Xapian::doclength get_average_length() const {
#ifdef XAPIAN_ASSERTIONS
        finalised = true;
#endif
        if (rare(collection_size == 0)) return 0;
        return Xapian::doclength(total_length) / collection_size;
    }

    void set_bounds_from_db(const Xapian::Database &db_) {
        Assert(!finalised);
        db = db_;
    }

    std::string get_description() const;
};

}

#endif // XAPIAN_INCLUDED_WEIGHTINTERNAL_H