collapser.h

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/* Copyright (C) 2009,2011 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_COLLAPSER_H
#define XAPIAN_INCLUDED_COLLAPSER_H

#include "backends/document.h"
#include "msetcmp.h"
#include "api/omenquireinternal.h"
#include "api/postlist.h"

#include <map>
#include <vector>

typedef enum {
    EMPTY,
    ADDED,
    REJECTED,
    REPLACED
} collapse_result;

class CollapseData {
    std::vector<Xapian::Internal::MSetItem> items;

    double next_best_weight;

    Xapian::doccount collapse_count;

  public:
    explicit CollapseData(const Xapian::Internal::MSetItem & item)
        : items(1, item), next_best_weight(0), collapse_count(0) {
        items[0].collapse_key = std::string();
    }

    collapse_result add_item(const Xapian::Internal::MSetItem & item,
                             Xapian::doccount collapse_max,
                             MSetCmp mcmp,
                             Xapian::Internal::MSetItem & old_item);

    double get_next_best_weight() const { return next_best_weight; }

    Xapian::doccount get_collapse_count() const { return collapse_count; }
};

class Collapser {
    std::map<std::string, CollapseData> table;

    Xapian::doccount entry_count;

    Xapian::doccount no_collapse_key;

    Xapian::doccount dups_ignored;

    Xapian::doccount docs_considered;

    Xapian::valueno slot;

    Xapian::doccount collapse_max;

  public:
    Xapian::Internal::MSetItem old_item;

    Collapser(Xapian::valueno slot_, Xapian::doccount collapse_max_)
        : entry_count(0), no_collapse_key(0), dups_ignored(0),
          docs_considered(0), slot(slot_), collapse_max(collapse_max_),
          old_item(0, 0) { }

    operator bool() const { return collapse_max != 0; }

    collapse_result process(Xapian::Internal::MSetItem & item,
                            PostList * postlist,
                            Xapian::Document::Internal & vsdoc,
                            MSetCmp mcmp);

    Xapian::doccount get_collapse_count(const std::string & collapse_key,
                                        int percent_cutoff,
                                        double min_weight) const;

    Xapian::doccount get_docs_considered() const { return docs_considered; }

    Xapian::doccount get_dups_ignored() const { return dups_ignored; }

    Xapian::doccount entries() const { return entry_count; }

    Xapian::doccount get_matches_lower_bound() const;

    bool empty() const { return table.empty(); }
};

#endif // XAPIAN_INCLUDED_COLLAPSER_H