xapian-core/api/decvalwtsource.cc

   1 /** @file
   2  * @brief A posting source which returns decreasing weights from a value.
   3  */
   4 /* Copyright (C) 2009 Lemur Consulting Ltd
   5  * Copyright (C) 2011,2012,2015,2016,2024 Olly Betts
   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 #include <config.h>
  23
  24 #include "xapian/postingsource.h"
  25 #include "pack.h"
  26
  27 using namespace Xapian;
  28
  29 DecreasingValueWeightPostingSource::DecreasingValueWeightPostingSource(
  30     Xapian::valueno slot_,
  31     Xapian::docid range_start_,
  32     Xapian::docid range_end_)
  33         : Xapian::ValueWeightPostingSource(slot_),
  34           range_start(range_start_),
  35           range_end(range_end_)
  36 {
  37 }
  38
  39 double
  40 DecreasingValueWeightPostingSource::get_weight() const {
  41     return curr_weight;
  42 }
  43
  44 Xapian::DecreasingValueWeightPostingSource *
  45 DecreasingValueWeightPostingSource::clone() const {
  46     return new DecreasingValueWeightPostingSource(get_slot(), range_start,
  47                                                   range_end);
  48 }
  49
  50 std::string
  51 DecreasingValueWeightPostingSource::name() const {
  52     return "Xapian::DecreasingValueWeightPostingSource";
  53 }
  54
  55 std::string
  56 DecreasingValueWeightPostingSource::serialise() const {
  57     std::string result;
  58     pack_uint(result, get_slot());
  59     pack_uint(result, range_start);
  60     pack_uint_last(result, range_end);
  61     return result;
  62 }
  63
  64 Xapian::DecreasingValueWeightPostingSource *
  65 DecreasingValueWeightPostingSource::unserialise(const std::string &s) const {
  66     const char * pos = s.data();
  67     const char * end = pos + s.size();
  68     Xapian::valueno new_slot;
  69     Xapian::docid new_range_start, new_range_end;
  70     if (!unpack_uint(&pos, end, &new_slot) ||
  71         !unpack_uint(&pos, end, &new_range_start) ||
  72         !unpack_uint_last(&pos, end, &new_range_end)) {
  73         unpack_throw_serialisation_error(pos);
  74     }
  75     return new DecreasingValueWeightPostingSource(new_slot, new_range_start,
  76                                                   new_range_end);
  77 }
  78
  79 void
  80 DecreasingValueWeightPostingSource::reset(const Xapian::Database& db_,
  81                                           Xapian::doccount shard_index)
  82 {
  83     Xapian::ValueWeightPostingSource::reset(db_, shard_index);
  84     if (range_end == 0 || get_database().get_doccount() <= range_end)
  85         items_at_end = false;
  86     else
  87         items_at_end = true;
  88 }
  89
  90 void
  91 DecreasingValueWeightPostingSource::skip_if_in_range(double min_wt)
  92 {
  93     if (ValueWeightPostingSource::at_end()) return;
  94     curr_weight = Xapian::ValueWeightPostingSource::get_weight();
  95     Xapian::docid docid = Xapian::ValueWeightPostingSource::get_docid();
  96     if (docid >= range_start && (range_end == 0 || docid <= range_end)) {
  97         if (items_at_end) {
  98             if (curr_weight < min_wt) {
  99                 // skip to end of range.
 100                 ValueWeightPostingSource::skip_to(range_end + 1, min_wt);
 101                 if (!ValueWeightPostingSource::at_end())
 102                     curr_weight = Xapian::ValueWeightPostingSource::get_weight();
 103             }
 104         } else {
 105             if (curr_weight < min_wt) {
 106                 // terminate early.
 107                 done();
 108             } else {
 109                 // Update max_weight.
 110                 set_maxweight(curr_weight);
 111             }
 112         }
 113     }
 114 }
 115
 116 void
 117 DecreasingValueWeightPostingSource::next(double min_wt) {
 118     if (get_maxweight() < min_wt) {
 119         done();
 120         return;
 121     }
 122     Xapian::ValueWeightPostingSource::next(min_wt);
 123     skip_if_in_range(min_wt);
 124 }
 125
 126 void
 127 DecreasingValueWeightPostingSource::skip_to(Xapian::docid min_docid,
 128                                             double min_wt) {
 129     if (get_maxweight() < min_wt) {
 130         done();
 131         return;
 132     }
 133     Xapian::ValueWeightPostingSource::skip_to(min_docid, min_wt);
 134     skip_if_in_range(min_wt);
 135 }
 136
 137 bool
 138 DecreasingValueWeightPostingSource::check(Xapian::docid min_docid,
 139                                           double min_wt) {
 140     if (get_maxweight() < min_wt) {
 141         done();
 142         return true;
 143     }
 144     bool valid = Xapian::ValueWeightPostingSource::check(min_docid, min_wt);
 145     if (valid) {
 146         skip_if_in_range(min_wt);
 147     }
 148     return valid;
 149 }
 150
 151 std::string
 152 DecreasingValueWeightPostingSource::get_description() const {
 153     return "DecreasingValueWeightPostingSource()";
 154 }