xapian-core/matcher/nearpostlist.h

   1 /** @file
   2  * @brief Return docs containing terms within a specified window.
   3  *
   4  * Copyright (C) 2006,2015 Olly Betts
   5  * Copyright (C) 2009 Lemur Consulting Ltd
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  20  */
  21
  22 #ifndef XAPIAN_INCLUDED_NEARPOSTLIST_H
  23 #define XAPIAN_INCLUDED_NEARPOSTLIST_H
  24
  25 #include "selectpostlist.h"
  26 #include <vector>
  27
  28 /** Postlist which matches terms occurring within a specified window.
  29  *
  30  *  NearPostList only returns a posting for documents contains all the terms
  31  *  (this part is implemented using an AndPostList) and additionally the terms
  32  *  occur somewhere in the document within a specified number of term
  33  *  positions.
  34  *
  35  *  The weight of a posting is the sum of the weights of the
  36  *  sub-postings (just like an AndPostList).
  37  */
  38 class NearPostList : public SelectPostList {
  39     Xapian::termpos window;
  40
  41     std::vector<PostList*> terms;
  42
  43     PositionList ** poslists;
  44
  45     /// Test if the current document contains the terms within the window.
  46     bool test_doc();
  47
  48   public:
  49     NearPostList(PostList *source_,
  50                  Xapian::termpos window_,
  51                  const std::vector<PostList*>::const_iterator &terms_begin,
  52                  const std::vector<PostList*>::const_iterator &terms_end);
  53
  54     ~NearPostList();
  55
  56     Xapian::termcount get_wdf() const;
  57
  58     Xapian::doccount get_termfreq_est() const;
  59
  60     TermFreqs get_termfreq_est_using_stats(
  61         const Xapian::Weight::Internal & stats) const;
  62
  63     std::string get_description() const;
  64 };
  65
  66 #endif