matcher/andmaybepostlist.h

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/* andmaybepostlist.h: Merged postlist: items from one list, weights from both
 *
 * AND MAYBE of two posting lists
 * A AND MAYBE B is logically just A, but we keep B around for weight purposes
 *
 * Copyright 1999,2000,2001 BrightStation PLC
 * Copyright 2002 Ananova Ltd
 * Copyright 2003,2004,2009 Olly Betts
 * Copyright 2009 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
 */


#ifndef OM_HGUARD_ANDMAYBEPOSTLIST_H
#define OM_HGUARD_ANDMAYBEPOSTLIST_H

#include "branchpostlist.h"

class AndMaybePostList : public BranchPostList {
    private:
        Xapian::doccount dbsize; // only need in case we decay to an AndPostList
        Xapian::docid lhead, rhead;
        Xapian::weight lmax, rmax;

        PostList * process_next_or_skip_to(Xapian::weight w_min, PostList *ret);
    public:
        Xapian::doccount get_termfreq_max() const;
        Xapian::doccount get_termfreq_min() const;
        Xapian::doccount get_termfreq_est() const;

        TermFreqs get_termfreq_est_using_stats(
            const Xapian::Weight::Internal & stats) const;

        Xapian::docid  get_docid() const;
        Xapian::weight get_weight() const;
        Xapian::weight get_maxweight() const;

        Xapian::weight recalc_maxweight();

        PostList *next(Xapian::weight w_min);
        PostList *skip_to(Xapian::docid did, Xapian::weight w_min);
        bool   at_end() const;

        std::string get_description() const;

        virtual Xapian::termcount get_doclength() const;

        AndMaybePostList(PostList *left_,
                         PostList *right_,
                         MultiMatch *matcher_,
                         Xapian::doccount dbsize_)
                : BranchPostList(left_, right_, matcher_),
                  dbsize(dbsize_), lhead(0), rhead(0)
        {
            // lmax and rmax will get initialised by a recalc_maxweight
        }

        AndMaybePostList(PostList *left_,
                         PostList *right_,
                         MultiMatch *matcher_,
                         Xapian::doccount dbsize_,
                         Xapian::docid lhead_,
                         Xapian::docid rhead_)
                : BranchPostList(left_, right_, matcher_),
                  dbsize(dbsize_), lhead(lhead_), rhead(rhead_)
        {
            // Initialise the maxweights from the kids so we can avoid forcing
            // a full maxweight recalc
            lmax = l->get_maxweight();
            rmax = r->get_maxweight();
        }

        PostList * sync_rhs(Xapian::weight w_min);

        Xapian::termcount get_wdf() const;

        Xapian::termcount count_matching_subqs() const;
};

#endif /* OM_HGUARD_ANDMAYBEPOSTLIST_H */

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