multi_postlist.h

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/* Copyright (C) 2007,2008,2009,2011,2015,2017,2020 Olly Betts
 * Copyright (C) 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, see
 * <https://www.gnu.org/licenses/>.
 */
 
#ifndef XAPIAN_INCLUDED_MULTI_POSTLIST_H
#define XAPIAN_INCLUDED_MULTI_POSTLIST_H
 
#include <string>
 
#include "backends/postlist.h"
#include "backends/positionlist.h"
 
class MultiPostList : public PostList {
    void operator=(const MultiPostList &) = delete;
 
    MultiPostList(const MultiPostList &) = delete;
 
    Xapian::doccount n_shards;
 
    PostList** postlists;
 
    Xapian::doccount docids_size = 0;
 
    Xapian::docid* docids = nullptr;
 
  public:
    MultiPostList(Xapian::doccount n_shards_, PostList** postlists_)
        : n_shards(n_shards_), postlists(postlists_)
    {
        try {
            docids = new Xapian::docid[n_shards];
        } catch (...) {
            delete [] postlists;
            throw;
        }
        // MultiPostList is only used by PostingIterator which should never
        // read the termfreq so leave it uninitialised so that ubsan or
        // valgrind can at least pick up unintended uses.
#if 0
        termfreq = 0;
        for (Xapian::doccount i = 0; i < n_shards_; ++i) {
            termfreq += postlists[i]->get_termfreq();
        }
#endif
    }
 
    ~MultiPostList();
 
    Xapian::docid get_docid() const;
 
    Xapian::termcount get_wdf() const;
 
    double get_weight(Xapian::termcount doclen,
                      Xapian::termcount unique_terms,
                      Xapian::termcount wdfdocmax) const;
 
    bool at_end() const;
 
    double recalc_maxweight();
 
    PositionList * open_position_list() const;
 
    PostList* next(double w_min);
 
    PostList* skip_to(Xapian::docid, double w_min);
 
    // We don't implement check() because we're only used in a PostingIterator
    // wrapper and that doesn't call check().
    //
    // Should that change, we could handle check() a bit more efficiently with
    // some extra bookkeeping on operations after check(), because we know
    // which subdatabase a given docid will be in, and so we only actually need
    // to call check() on that subdatabase.
 
    std::string get_description() const;
};
 
#endif // XAPIAN_INCLUDED_MULTI_POSTLIST_H