xapian-core/matcher/msetcmp.cc

   1 /** @file
   2  * @brief Result comparison functions.
   3  */
   4 /* Copyright (C) 2006,2009,2013,2017 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
  19  * USA
  20  */
  21
  22 #include <config.h>
  23
  24 #include "msetcmp.h"
  25
  26 #include "api/result.h"
  27 #include "omassert.h"
  28
  29 /* We use templates to generate all the different comparison functions which we
  30  * need, which avoids having to write them all out by hand.
  31  */
  32
  33 // Order by docid, inlined.  Used as the last fallback by the others.
  34 template<bool FORWARD_DID>
  35 static inline bool
  36 msetcmp_by_docid_inline(const Result& a, const Result& b)
  37 {
  38     if (FORWARD_DID) {
  39         return (a.get_docid() < b.get_docid());
  40     } else {
  41         return (a.get_docid() > b.get_docid());
  42     }
  43 }
  44
  45 // Order by docid, used when relevance is always 0.
  46 template<bool FORWARD_DID>
  47 static bool
  48 msetcmp_by_docid(const Result& a, const Result& b)
  49 {
  50     return msetcmp_by_docid_inline<FORWARD_DID>(a, b);
  51 }
  52
  53 // Order by relevance, then docid.
  54 template<bool FORWARD_DID>
  55 static bool
  56 msetcmp_by_relevance(const Result& a, const Result& b)
  57 {
  58     if (a.get_weight() > b.get_weight()) return true;
  59     if (a.get_weight() < b.get_weight()) return false;
  60     return msetcmp_by_docid_inline<FORWARD_DID>(a, b);
  61 }
  62
  63 // Order by value, then docid.
  64 template<bool FORWARD_VALUE, bool FORWARD_DID>
  65 static bool
  66 msetcmp_by_value(const Result& a, const Result& b)
  67 {
  68     int sort_cmp = a.get_sort_key().compare(b.get_sort_key());
  69     if (sort_cmp > 0) return FORWARD_VALUE;
  70     if (sort_cmp < 0) return !FORWARD_VALUE;
  71     return msetcmp_by_docid_inline<FORWARD_DID>(a, b);
  72 }
  73
  74 // Order by value, then relevance, then docid.
  75 template<bool FORWARD_VALUE, bool FORWARD_DID>
  76 static bool
  77 msetcmp_by_value_then_relevance(const Result& a, const Result& b)
  78 {
  79     int sort_cmp = a.get_sort_key().compare(b.get_sort_key());
  80     if (sort_cmp > 0) return FORWARD_VALUE;
  81     if (sort_cmp < 0) return !FORWARD_VALUE;
  82     if (a.get_weight() > b.get_weight()) return true;
  83     if (a.get_weight() < b.get_weight()) return false;
  84     return msetcmp_by_docid_inline<FORWARD_DID>(a, b);
  85 }
  86
  87 // Order by relevance, then value, then docid.
  88 template<bool FORWARD_VALUE, bool FORWARD_DID>
  89 static bool
  90 msetcmp_by_relevance_then_value(const Result& a, const Result& b)
  91 {
  92     if (a.get_weight() > b.get_weight()) return true;
  93     if (a.get_weight() < b.get_weight()) return false;
  94     int sort_cmp = a.get_sort_key().compare(b.get_sort_key());
  95     if (sort_cmp > 0) return FORWARD_VALUE;
  96     if (sort_cmp < 0) return !FORWARD_VALUE;
  97     return msetcmp_by_docid_inline<FORWARD_DID>(a, b);
  98 }
  99
 100 MSetCmp
 101 get_msetcmp_function(Xapian::Enquire::Internal::sort_setting sort_by,
 102                      bool sort_forward,
 103                      bool sort_val_reverse)
 104 {
 105     switch (sort_by) {
 106         case Xapian::Enquire::Internal::DOCID:
 107             if (sort_forward)
 108                 return msetcmp_by_docid<true>;
 109             else
 110                 return msetcmp_by_docid<false>;
 111         case Xapian::Enquire::Internal::REL:
 112             if (sort_forward)
 113                 return msetcmp_by_relevance<true>;
 114             else
 115                 return msetcmp_by_relevance<false>;
 116         case Xapian::Enquire::Internal::VAL:
 117             if (sort_forward) {
 118                 if (sort_val_reverse) {
 119                     return msetcmp_by_value<true, true>;
 120                 } else {
 121                     return msetcmp_by_value<false, true>;
 122                 }
 123             } else {
 124                 if (sort_val_reverse) {
 125                     return msetcmp_by_value<true, false>;
 126                 } else {
 127                     return msetcmp_by_value<false, false>;
 128                 }
 129             }
 130         case Xapian::Enquire::Internal::VAL_REL:
 131             if (sort_forward) {
 132                 if (sort_val_reverse) {
 133                     return msetcmp_by_value_then_relevance<true, true>;
 134                 } else {
 135                     return msetcmp_by_value_then_relevance<false, true>;
 136                 }
 137             } else {
 138                 if (sort_val_reverse) {
 139                     return msetcmp_by_value_then_relevance<true, false>;
 140                 } else {
 141                     return msetcmp_by_value_then_relevance<false, false>;
 142                 }
 143             }
 144         default:
 145             // Must be REL_VAL, but handle with "default" to avoid warnings
 146             // about falling off the end of the function.
 147             AssertEq(sort_by, Xapian::Enquire::Internal::REL_VAL);
 148             if (sort_forward) {
 149                 if (sort_val_reverse) {
 150                     return msetcmp_by_relevance_then_value<true, true>;
 151                 } else {
 152                     return msetcmp_by_relevance_then_value<false, true>;
 153                 }
 154             } else {
 155                 if (sort_val_reverse) {
 156                     return msetcmp_by_relevance_then_value<true, false>;
 157                 } else {
 158                     return msetcmp_by_relevance_then_value<false, false>;
 159                 }
 160             }
 161     }
 162 }