xapian-core/matcher/extraweightpostlist.h

   1 /** @file
   2  * @brief add on extra weight contribution
   3  */
   4 /* Copyright 1999,2000,2001 BrightStation PLC
   5  * Copyright 2001 Ananova Ltd
   6  * Copyright 2003,2004,2007,2009,2011,2014 Olly Betts
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of the
  11  * License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
  21  * USA
  22  */
  23
  24 #ifndef OM_HGUARD_EXTRAWEIGHTPOSTLIST_H
  25 #define OM_HGUARD_EXTRAWEIGHTPOSTLIST_H
  26
  27 #include "multimatch.h"
  28 #include "omassert.h"
  29
  30 namespace Xapian {
  31     class Weight;
  32 }
  33
  34 /// A postlist which adds on an extra weight contribution
  35 class ExtraWeightPostList : public PostList {
  36     private:
  37         PostList * pl;
  38         Xapian::Weight * wt;
  39         MultiMatch * matcher;
  40         double max_weight;
  41
  42     public:
  43         Xapian::doccount get_termfreq_max() const {
  44             return pl->get_termfreq_max();
  45         }
  46         Xapian::doccount get_termfreq_min() const {
  47             return pl->get_termfreq_min();
  48         }
  49         Xapian::doccount get_termfreq_est() const {
  50             return pl->get_termfreq_est();
  51         }
  52
  53         Xapian::docid get_docid() const { return pl->get_docid(); }
  54
  55         double get_weight() const {
  56             /* Second parameter of get_sumextra is number of unique terms in doc, which has been put
  57              * to maintain consistency with get_sumpart, As of now none of weighting scheme is using
  58              * it. Current 0 is being passed, change it to pl->get_unique_terms() in case you
  59              * need access uniq_terms. */
  60             double sumextra = wt->get_sumextra(pl->get_doclength(), 0);
  61             AssertRel(sumextra, <=, max_weight);
  62             return pl->get_weight() + sumextra;
  63         }
  64
  65         double get_maxweight() const {
  66             return pl->get_maxweight() + max_weight;
  67         }
  68
  69         double recalc_maxweight() {
  70             return pl->recalc_maxweight() + max_weight;
  71         }
  72
  73         PostList *next(double w_min) {
  74             PostList *p = pl->next(w_min - max_weight);
  75             if (p) {
  76                 delete pl;
  77                 pl = p;
  78                 if (matcher) matcher->recalc_maxweight();
  79             }
  80             return NULL;
  81         }
  82
  83         PostList *skip_to(Xapian::docid did, double w_min) {
  84             PostList *p = pl->skip_to(did, w_min - max_weight);
  85             if (p) {
  86                 delete pl;
  87                 pl = p;
  88                 if (matcher) matcher->recalc_maxweight();
  89             }
  90             return NULL;
  91         }
  92
  93         bool at_end() const { return pl->at_end(); }
  94
  95         std::string get_description() const {
  96             return "( ExtraWeight " + pl->get_description() + " )";
  97         }
  98
  99         /** Return the document length of the document the current term
 100          *  comes from.
 101          */
 102         virtual Xapian::termcount get_doclength() const {
 103             return pl->get_doclength();
 104         }
 105
 106         virtual Xapian::termcount get_unique_terms() const {
 107             return pl->get_unique_terms();
 108         }
 109
 110         ExtraWeightPostList(PostList * pl_, Xapian::Weight *wt_,
 111                             MultiMatch *matcher_)
 112             : pl(pl_), wt(wt_), matcher(matcher_),
 113               max_weight(wt->get_maxextra())
 114         { }
 115
 116         ~ExtraWeightPostList() {
 117             delete pl;
 118             delete wt;
 119         }
 120
 121         Xapian::termcount count_matching_subqs() const {
 122             return pl->count_matching_subqs();
 123         }
 124 };
 125
 126 #endif /* OM_HGUARD_EXTRAWEIGHTPOSTLIST_H */