xapian-core/matcher/nearpostlist.h

   1 /** @file
   2  * @brief Return docs containing terms within a specified window.
   3  *
   4  * Copyright (C) 2006,2015,2017 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 class EstimateOp;
  29 class PostListTree;
  30
  31 /** Postlist which matches terms occurring within a specified window.
  32  *
  33  *  NearPostList only returns a posting for documents contains all the terms
  34  *  (this part is implemented using an AndPostList) and additionally the terms
  35  *  occur somewhere in the document within a specified number of term
  36  *  positions.
  37  *
  38  *  The weight of a posting is the sum of the weights of the
  39  *  sub-postings (just like an AndPostList).
  40  */
  41 class NearPostList : public SelectPostList {
  42     Xapian::termpos window;
  43
  44     std::vector<PostList*> terms;
  45
  46     PositionList ** poslists;
  47
  48     /// Test if the current document contains the terms within the window.
  49     bool test_doc();
  50
  51   public:
  52     NearPostList(PostList *source_,
  53                  EstimateOp* estimate_op_,
  54                  Xapian::termpos window_,
  55                  const std::vector<PostList*>::const_iterator &terms_begin,
  56                  const std::vector<PostList*>::const_iterator &terms_end,
  57                  PostListTree* pltree_);
  58
  59     ~NearPostList();
  60
  61     Xapian::termcount get_wdf() const;
  62
  63     std::string get_description() const;
  64 };
  65
  66 #endif