xapian-core/matcher/orpostlist.h

   1 /** @file orpostlist.h
   2  * @brief OR of two posting lists
   3  */
   4 /* Copyright 1999,2000,2001 BrightStation PLC
   5  * Copyright 2002 Ananova Ltd
   6  * Copyright 2003,2004,2009,2010,2011 Olly Betts
   7  * Copyright 2009 Lemur Consulting Ltd
   8  * Copyright 2010 Richard Boulton
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public License as
  12  * published by the Free Software Foundation; either version 2 of the
  13  * License, or (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
  23  * USA
  24  */
  25
  26 #ifndef OM_HGUARD_ORPOSTLIST_H
  27 #define OM_HGUARD_ORPOSTLIST_H
  28
  29 #include "branchpostlist.h"
  30
  31 /** A postlist comprising two postlists ORed together.
  32  *
  33  *  This postlist returns a posting if it is in either of the sub-postlists.
  34  *  The weight for a posting is the sum of the weights of the sub-postings,
  35  *  if both exist, or the sum of the single sub-posting which exists
  36  *  otherwise.
  37  */
  38 class OrPostList : public BranchPostList {
  39     private:
  40         Xapian::docid lhead, rhead;
  41         bool lvalid, rvalid;
  42         double lmax, rmax, minmax;
  43         Xapian::doccount dbsize;
  44     public:
  45         Xapian::doccount get_termfreq_max() const;
  46         Xapian::doccount get_termfreq_min() const;
  47         Xapian::doccount get_termfreq_est() const;
  48         TermFreqs get_termfreq_est_using_stats(
  49             const Xapian::Weight::Internal & stats) const;
  50
  51         Xapian::docid get_docid() const;
  52         double get_weight() const;
  53         double get_maxweight() const;
  54
  55         double recalc_maxweight();
  56
  57         PostList *next(double w_min);
  58         PostList *skip_to(Xapian::docid did, double w_min);
  59         PostList *check(Xapian::docid did, double w_min, bool &valid);
  60         bool at_end() const;
  61
  62         std::string get_description() const;
  63
  64         /** Return the document length of the document the current term
  65          *  comes from.
  66          *
  67          *  This is obtained by asking the subpostlist which contains the
  68          *  current document for the document length.  If both subpostlists
  69          *  are valid, the left one is asked.
  70          */
  71         virtual Xapian::termcount get_doclength() const;
  72
  73         /// Return the number of unique terms in the document.
  74         virtual Xapian::termcount get_unique_terms() const;
  75
  76         OrPostList(PostList * left_,
  77                    PostList * right_,
  78                    MultiMatch * matcher_,
  79                    Xapian::doccount dbsize_);
  80
  81         /** get_wdf() for OR postlists returns the sum of the wdfs of the
  82          *  sub postlists which are at the current document - this is desirable
  83          *  when the OR is part of a synonym.
  84          */
  85         Xapian::termcount get_wdf() const;
  86
  87         Xapian::termcount count_matching_subqs() const;
  88 };
  89
  90 #endif /* OM_HGUARD_ORPOSTLIST_H */