matcher/multiandpostlist.h

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/* Copyright (C) 2007 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_MULTIANDPOSTLIST_H
#define XAPIAN_INCLUDED_MULTIANDPOSTLIST_H

#include "multimatch.h"
#include "postlist.h"

class MultiAndPostList : public PostList {
    struct ComparePostListTermFreqAscending {
        bool operator()(const PostList *a, const PostList *b) {
            return a->get_termfreq_est() < b->get_termfreq_est();
        }
    };

    void operator=(const MultiAndPostList &);

    MultiAndPostList(const MultiAndPostList &);

    Xapian::docid did;

    size_t n_kids;

    PostList ** plist;

    Xapian::weight * max_wt;

    Xapian::weight max_total;

    Xapian::doccount db_size;

    MultiMatch *matcher;

    Xapian::weight new_min(Xapian::weight w_min, size_t n) {
        return w_min - (max_total - max_wt[n]);
    }

    void next_helper(size_t n, Xapian::weight w_min) {
        PostList * res = plist[n]->next(new_min(w_min, n));
        if (res) {
            delete plist[n];
            plist[n] = res;
            matcher->recalc_maxweight();
        }
    }

    void skip_to_helper(size_t n, Xapian::docid did_min, Xapian::weight w_min) {
        PostList * res = plist[n]->skip_to(did_min, new_min(w_min, n));
        if (res) {
            delete plist[n];
            plist[n] = res;
            matcher->recalc_maxweight();
        }
    }

    void check_helper(size_t n, Xapian::docid did_min, Xapian::weight w_min,
                      bool &valid) {
        PostList * res = plist[n]->check(did_min, new_min(w_min, n), valid);
        if (res) {
            delete plist[n];
            plist[n] = res;
            matcher->recalc_maxweight();
        }
    }

    PostList * find_next_match(Xapian::weight w_min);

  public:
    template <class RandomItor>
    MultiAndPostList(RandomItor pl_begin, RandomItor pl_end,
                     MultiMatch * matcher_, Xapian::doccount db_size_)
        : did(0), n_kids(pl_end - pl_begin), plist(NULL), max_wt(NULL),
          max_total(0), db_size(db_size_), matcher(matcher_)
    {
        plist = new PostList * [n_kids];
        try {
            max_wt = new Xapian::weight [n_kids];
        } catch (...) {
            delete [] plist;
            plist = NULL;
            throw;
        }

        // Copy the postlists in ascending termfreq order, since it will
        // be more efficient to look at the shorter lists first, and skip
        // the longer lists based on those.
        std::partial_sort_copy(pl_begin, pl_end, plist, plist + n_kids,
                               ComparePostListTermFreqAscending());
    }

    ~MultiAndPostList();

    Xapian::doccount get_termfreq_min() const;

    Xapian::doccount get_termfreq_max() const;

    Xapian::doccount get_termfreq_est() const;

    Xapian::weight get_maxweight() const;

    Xapian::docid get_docid() const;

    Xapian::doclength get_doclength() const;

    Xapian::weight get_weight() const;

    bool at_end() const;

    Xapian::weight recalc_maxweight();

    Internal *next(Xapian::weight w_min);

    Internal *skip_to(Xapian::docid, Xapian::weight w_min);

    std::string get_description() const;

    virtual Xapian::termcount get_wdf() const;
};

#endif // XAPIAN_INCLUDED_MULTIANDPOSTLIST_H

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