xapian-core/matcher/andnotpostlist.h

   1 /** @file
   2  * @brief Return items which are in A, unless they're in B
   3  */
   4 /* Copyright 1999,2000,2001 BrightStation PLC
   5  * Copyright 2002 Ananova Ltd
   6  * Copyright 2003,2004,2009,2011 Olly Betts
   7  * Copyright 2009 Lemur Consulting Ltd
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License as
  11  * published by the Free Software Foundation; either version 2 of the
  12  * License, or (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
  22  * USA
  23  */
  24
  25 #ifndef OM_HGUARD_ANDNOTPOSTLIST_H
  26 #define OM_HGUARD_ANDNOTPOSTLIST_H
  27
  28 #include "branchpostlist.h"
  29
  30 /** A postlist generated by taking one postlist (the left-hand postlist),
  31  *  and removing any documents which are in the other (right-hand) postlist.
  32  *
  33  *  The weight for a posting is the weight in the left-hand postlist.
  34  */
  35 class AndNotPostList : public BranchPostList {
  36     private:
  37         Xapian::docid lhead, rhead;
  38
  39         /// Number of documents in the database this postlist is across
  40         Xapian::doccount dbsize;
  41
  42         PostList *advance_to_next_match(double w_min, PostList *ret);
  43     public:
  44         Xapian::doccount get_termfreq_max() const;
  45         Xapian::doccount get_termfreq_min() const;
  46         Xapian::doccount get_termfreq_est() const;
  47         TermFreqs get_termfreq_est_using_stats(
  48             const Xapian::Weight::Internal & stats) const;
  49
  50         Xapian::docid get_docid() const;
  51         double get_weight() const;
  52         double get_maxweight() const;
  53
  54         double recalc_maxweight();
  55
  56         PostList *next(double w_min);
  57         PostList *skip_to(Xapian::docid did, double w_min);
  58         bool at_end() const;
  59
  60         std::string get_description() const;
  61
  62         /** Return the document length of the document the current term
  63          *  comes from.
  64          */
  65         virtual Xapian::termcount get_doclength() const;
  66
  67         virtual Xapian::termcount get_unique_terms() const;
  68
  69         AndNotPostList(PostList *left,
  70                        PostList *right,
  71                        MultiMatch *matcher_,
  72                        Xapian::doccount dbsize_);
  73
  74         PostList *sync_and_skip_to(Xapian::docid id,
  75                                    double w_min,
  76                                    Xapian::docid lh,
  77                                    Xapian::docid rh);
  78
  79         /** get_wdf() for ANDNOT postlists returns the wdf of the left hand
  80          * side.
  81          */
  82         Xapian::termcount get_wdf() const;
  83
  84         Xapian::termcount count_matching_subqs() const;
  85 };
  86
  87 #endif /* OM_HGUARD_ANDNOTPOSTLIST_H */