xapian-core/matcher/extraweightpostlist.cc

   1 /** @file extraweightpostlist.cc
   2  * @brief PostList which adds on a term-independent weight contribution
   3  */
   4 /* Copyright 2017 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation; either version 2 of the
   9  * License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  19  */
  20
  21 #include <config.h>
  22
  23 #include "extraweightpostlist.h"
  24
  25 #include "omassert.h"
  26 #include "postlisttree.h"
  27 #include "str.h"
  28
  29 using namespace std;
  30
  31 double
  32 ExtraWeightPostList::get_weight(Xapian::termcount doclen,
  33                                 Xapian::termcount unique_terms) const
  34 {
  35     /* Weight::get_sumextra() takes two parameters (document length and number
  36      * of unique terms) but none of the currently implemented weighting schemes
  37      * actually use the latter - it was added because it's likely to be wanted
  38      * at some point, and so that we got all the incompatible changes needed to
  39      * add support for the number of unique terms over with in one go.
  40      */
  41     double sum_extra = weight->get_sumextra(doclen, unique_terms);
  42     AssertRel(sum_extra,<=,max_extra);
  43     return pl->get_weight(doclen, unique_terms) + sum_extra;
  44 }
  45
  46 double
  47 ExtraWeightPostList::recalc_maxweight()
  48 {
  49     return pl->recalc_maxweight() + max_extra;
  50 }
  51
  52 PostList*
  53 ExtraWeightPostList::next(double w_min)
  54 {
  55     PostList* res = pl->next(w_min - max_extra);
  56     if (res) {
  57         delete pl;
  58         pl = res;
  59         pltree->force_recalc();
  60     }
  61     return NULL;
  62 }
  63
  64 PostList*
  65 ExtraWeightPostList::skip_to(Xapian::docid, double)
  66 {
  67     // ExtraWeightPostList's parent will be PostListTree which doesn't
  68     // call skip_to() or check().
  69     Assert(false);
  70     return NULL;
  71 }
  72
  73 string
  74 ExtraWeightPostList::get_description() const
  75 {
  76     string desc = "ExtraWeightPostList(";
  77     desc += pl->get_description();
  78     desc += ", max_extra=";
  79     desc += str(max_extra);
  80     desc += ')';
  81     return desc;
  82 }