xapian-core/matcher/msetcmp.cc

   1 /** @file
   2  * @brief MSetItem 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 #include "msetcmp.h"
  24
  25 #include "omassert.h"
  26
  27 /* We use templates to generate the 14 different comparison functions
  28  * which we need.  This avoids having to write them all out by hand.
  29  */
  30
  31 // Order by did.  Helper comparison template function, which is used as the
  32 // last fallback by the others.
  33 template<bool FORWARD_DID, bool CHECK_DID_ZERO>
  34 static inline bool
  35 msetcmp_by_did(const Xapian::Internal::MSetItem &a,
  36                const Xapian::Internal::MSetItem &b)
  37 {
  38     if (FORWARD_DID) {
  39         if (CHECK_DID_ZERO) {
  40             // We want dummy did 0 to compare worse than any other.
  41             if (a.did == 0) return false;
  42             if (b.did == 0) return true;
  43         }
  44         return (a.did < b.did);
  45     } else {
  46         return (a.did > b.did);
  47     }
  48 }
  49
  50 // Order by relevance, then docid.
  51 template<bool FORWARD_DID>
  52 static bool
  53 msetcmp_by_relevance(const Xapian::Internal::MSetItem &a,
  54                      const Xapian::Internal::MSetItem &b)
  55 {
  56     if (a.wt > b.wt) return true;
  57     if (a.wt < b.wt) return false;
  58     return msetcmp_by_did<FORWARD_DID, true>(a, b);
  59 }
  60
  61 // Order by value, then docid.
  62 template<bool FORWARD_VALUE, bool FORWARD_DID>
  63 static bool
  64 msetcmp_by_value(const Xapian::Internal::MSetItem &a,
  65                  const Xapian::Internal::MSetItem &b)
  66 {
  67     if (!FORWARD_VALUE) {
  68         // We want dummy did 0 to compare worse than any other.
  69         if (a.did == 0) return false;
  70         if (b.did == 0) return true;
  71     }
  72     int sort_cmp = a.sort_key.compare(b.sort_key);
  73     if (sort_cmp > 0) return FORWARD_VALUE;
  74     if (sort_cmp < 0) return !FORWARD_VALUE;
  75     return msetcmp_by_did<FORWARD_DID, FORWARD_VALUE>(a, b);
  76 }
  77
  78 // Order by value, then relevance, then docid.
  79 template<bool FORWARD_VALUE, bool FORWARD_DID>
  80 static bool
  81 msetcmp_by_value_then_relevance(const Xapian::Internal::MSetItem &a,
  82                                 const Xapian::Internal::MSetItem &b)
  83 {
  84     if (!FORWARD_VALUE) {
  85         // two special cases to make min_item compares work when did == 0
  86         if (a.did == 0) return false;
  87         if (b.did == 0) return true;
  88     }
  89     int sort_cmp = a.sort_key.compare(b.sort_key);
  90     if (sort_cmp > 0) return FORWARD_VALUE;
  91     if (sort_cmp < 0) return !FORWARD_VALUE;
  92     if (a.wt > b.wt) return true;
  93     if (a.wt < b.wt) return false;
  94     return msetcmp_by_did<FORWARD_DID, FORWARD_VALUE>(a, b);
  95 }
  96
  97 // Order by relevance, then value, then docid.
  98 template<bool FORWARD_VALUE, bool FORWARD_DID>
  99 static bool
 100 msetcmp_by_relevance_then_value(const Xapian::Internal::MSetItem &a,
 101                                 const Xapian::Internal::MSetItem &b)
 102 {
 103     if (!FORWARD_VALUE) {
 104         // two special cases to make min_item compares work when did == 0
 105         if (a.did == 0) return false;
 106         if (b.did == 0) return true;
 107     }
 108     if (a.wt > b.wt) return true;
 109     if (a.wt < b.wt) return false;
 110     int sort_cmp = a.sort_key.compare(b.sort_key);
 111     if (sort_cmp > 0) return FORWARD_VALUE;
 112     if (sort_cmp < 0) return !FORWARD_VALUE;
 113     return msetcmp_by_did<FORWARD_DID, FORWARD_VALUE>(a, b);
 114 }
 115
 116 MSetCmp
 117 get_msetcmp_function(Xapian::Enquire::Internal::sort_setting sort_by,
 118                      bool sort_forward,
 119                      bool sort_val_reverse)
 120 {
 121     switch (sort_by) {
 122         case Xapian::Enquire::Internal::REL:
 123             if (sort_forward)
 124                 return msetcmp_by_relevance<true>;
 125             else
 126                 return msetcmp_by_relevance<false>;
 127         case Xapian::Enquire::Internal::VAL:
 128             if (sort_forward) {
 129                 if (sort_val_reverse) {
 130                     return msetcmp_by_value<true, true>;
 131                 } else {
 132                     return msetcmp_by_value<false, true>;
 133                 }
 134             } else {
 135                 if (sort_val_reverse) {
 136                     return msetcmp_by_value<true, false>;
 137                 } else {
 138                     return msetcmp_by_value<false, false>;
 139                 }
 140             }
 141         case Xapian::Enquire::Internal::VAL_REL:
 142             if (sort_forward) {
 143                 if (sort_val_reverse) {
 144                     return msetcmp_by_value_then_relevance<true, true>;
 145                 } else {
 146                     return msetcmp_by_value_then_relevance<false, true>;
 147                 }
 148             } else {
 149                 if (sort_val_reverse) {
 150                     return msetcmp_by_value_then_relevance<true, false>;
 151                 } else {
 152                     return msetcmp_by_value_then_relevance<false, false>;
 153                 }
 154             }
 155         default:
 156             // Must be REL_VAL, but handle with "default" to avoid warnings
 157             // about falling off the end of the function.
 158             AssertEq(sort_by, Xapian::Enquire::Internal::REL_VAL);
 159             if (sort_forward) {
 160                 if (sort_val_reverse) {
 161                     return msetcmp_by_relevance_then_value<true, true>;
 162                 } else {
 163                     return msetcmp_by_relevance_then_value<false, true>;
 164                 }
 165             } else {
 166                 if (sort_val_reverse) {
 167                     return msetcmp_by_relevance_then_value<true, false>;
 168                 } else {
 169                     return msetcmp_by_relevance_then_value<false, false>;
 170                 }
 171             }
 172     }
 173 }