src/backend/access/nbtree/nbtcompare.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * nbtcompare.c
   4  *        Comparison functions for btree access method.
   5  *
   6  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $PostgreSQL$
  12  *
  13  * NOTES
  14  *
  15  *      These functions are stored in pg_amproc.  For each operator class
  16  *      defined on btrees, they compute
  17  *
  18  *                              compare(a, b):
  19  *                                              < 0 if a < b,
  20  *                                              = 0 if a == b,
  21  *                                              > 0 if a > b.
  22  *
  23  *      The result is always an int32 regardless of the input datatype.
  24  *
  25  *      Although any negative int32 (except INT_MIN) is acceptable for reporting
  26  *      "<", and any positive int32 is acceptable for reporting ">", routines
  27  *      that work on 32-bit or wider datatypes can't just return "a - b".
  28  *      That could overflow and give the wrong answer.  Also, one must not
  29  *      return INT_MIN to report "<", since some callers will negate the result.
  30  *
  31  *      NOTE: it is critical that the comparison function impose a total order
  32  *      on all non-NULL values of the data type, and that the datatype's
  33  *      boolean comparison operators (= < >= etc) yield results consistent
  34  *      with the comparison routine.  Otherwise bad behavior may ensue.
  35  *      (For example, the comparison operators must NOT punt when faced with
  36  *      NAN or other funny values; you must devise some collation sequence for
  37  *      all such values.)  If the datatype is not trivial, this is most
  38  *      reliably done by having the boolean operators invoke the same
  39  *      three-way comparison code that the btree function does.  Therefore,
  40  *      this file contains only btree support for "trivial" datatypes ---
  41  *      all others are in the /utils/adt/ files that implement their datatypes.
  42  *
  43  *      NOTE: these routines must not leak memory, since memory allocated
  44  *      during an index access won't be recovered till end of query.  This
  45  *      primarily affects comparison routines for toastable datatypes;
  46  *      they have to be careful to free any detoasted copy of an input datum.
  47  *-------------------------------------------------------------------------
  48  */
  49 #include "postgres.h"
  50
  51 #include "utils/builtins.h"
  52
  53
  54 Datum
  55 btboolcmp(PG_FUNCTION_ARGS)
  56 {
  57         bool            a = PG_GETARG_BOOL(0);
  58         bool            b = PG_GETARG_BOOL(1);
  59
  60         PG_RETURN_INT32((int32) a - (int32) b);
  61 }
  62
  63 Datum
  64 btint2cmp(PG_FUNCTION_ARGS)
  65 {
  66         int16           a = PG_GETARG_INT16(0);
  67         int16           b = PG_GETARG_INT16(1);
  68
  69         PG_RETURN_INT32((int32) a - (int32) b);
  70 }
  71
  72 Datum
  73 btint4cmp(PG_FUNCTION_ARGS)
  74 {
  75         int32           a = PG_GETARG_INT32(0);
  76         int32           b = PG_GETARG_INT32(1);
  77
  78         if (a > b)
  79                 PG_RETURN_INT32(1);
  80         else if (a == b)
  81                 PG_RETURN_INT32(0);
  82         else
  83                 PG_RETURN_INT32(-1);
  84 }
  85
  86 Datum
  87 btint8cmp(PG_FUNCTION_ARGS)
  88 {
  89         int64           a = PG_GETARG_INT64(0);
  90         int64           b = PG_GETARG_INT64(1);
  91
  92         if (a > b)
  93                 PG_RETURN_INT32(1);
  94         else if (a == b)
  95                 PG_RETURN_INT32(0);
  96         else
  97                 PG_RETURN_INT32(-1);
  98 }
  99
 100 Datum
 101 btint48cmp(PG_FUNCTION_ARGS)
 102 {
 103         int32           a = PG_GETARG_INT32(0);
 104         int64           b = PG_GETARG_INT64(1);
 105
 106         if (a > b)
 107                 PG_RETURN_INT32(1);
 108         else if (a == b)
 109                 PG_RETURN_INT32(0);
 110         else
 111                 PG_RETURN_INT32(-1);
 112 }
 113
 114 Datum
 115 btint84cmp(PG_FUNCTION_ARGS)
 116 {
 117         int64           a = PG_GETARG_INT64(0);
 118         int32           b = PG_GETARG_INT32(1);
 119
 120         if (a > b)
 121                 PG_RETURN_INT32(1);
 122         else if (a == b)
 123                 PG_RETURN_INT32(0);
 124         else
 125                 PG_RETURN_INT32(-1);
 126 }
 127
 128 Datum
 129 btint24cmp(PG_FUNCTION_ARGS)
 130 {
 131         int16           a = PG_GETARG_INT16(0);
 132         int32           b = PG_GETARG_INT32(1);
 133
 134         if (a > b)
 135                 PG_RETURN_INT32(1);
 136         else if (a == b)
 137                 PG_RETURN_INT32(0);
 138         else
 139                 PG_RETURN_INT32(-1);
 140 }
 141
 142 Datum
 143 btint42cmp(PG_FUNCTION_ARGS)
 144 {
 145         int32           a = PG_GETARG_INT32(0);
 146         int16           b = PG_GETARG_INT16(1);
 147
 148         if (a > b)
 149                 PG_RETURN_INT32(1);
 150         else if (a == b)
 151                 PG_RETURN_INT32(0);
 152         else
 153                 PG_RETURN_INT32(-1);
 154 }
 155
 156 Datum
 157 btint28cmp(PG_FUNCTION_ARGS)
 158 {
 159         int16           a = PG_GETARG_INT16(0);
 160         int64           b = PG_GETARG_INT64(1);
 161
 162         if (a > b)
 163                 PG_RETURN_INT32(1);
 164         else if (a == b)
 165                 PG_RETURN_INT32(0);
 166         else
 167                 PG_RETURN_INT32(-1);
 168 }
 169
 170 Datum
 171 btint82cmp(PG_FUNCTION_ARGS)
 172 {
 173         int64           a = PG_GETARG_INT64(0);
 174         int16           b = PG_GETARG_INT16(1);
 175
 176         if (a > b)
 177                 PG_RETURN_INT32(1);
 178         else if (a == b)
 179                 PG_RETURN_INT32(0);
 180         else
 181                 PG_RETURN_INT32(-1);
 182 }
 183
 184 Datum
 185 btoidcmp(PG_FUNCTION_ARGS)
 186 {
 187         Oid                     a = PG_GETARG_OID(0);
 188         Oid                     b = PG_GETARG_OID(1);
 189
 190         if (a > b)
 191                 PG_RETURN_INT32(1);
 192         else if (a == b)
 193                 PG_RETURN_INT32(0);
 194         else
 195                 PG_RETURN_INT32(-1);
 196 }
 197
 198 Datum
 199 btoidvectorcmp(PG_FUNCTION_ARGS)
 200 {
 201         oidvector  *a = (oidvector *) PG_GETARG_POINTER(0);
 202         oidvector  *b = (oidvector *) PG_GETARG_POINTER(1);
 203         int                     i;
 204
 205         /* We arbitrarily choose to sort first by vector length */
 206         if (a->dim1 != b->dim1)
 207                 PG_RETURN_INT32(a->dim1 - b->dim1);
 208
 209         for (i = 0; i < a->dim1; i++)
 210         {
 211                 if (a->values[i] != b->values[i])
 212                 {
 213                         if (a->values[i] > b->values[i])
 214                                 PG_RETURN_INT32(1);
 215                         else
 216                                 PG_RETURN_INT32(-1);
 217                 }
 218         }
 219         PG_RETURN_INT32(0);
 220 }
 221
 222 Datum
 223 btcharcmp(PG_FUNCTION_ARGS)
 224 {
 225         char            a = PG_GETARG_CHAR(0);
 226         char            b = PG_GETARG_CHAR(1);
 227
 228         /* Be careful to compare chars as unsigned */
 229         PG_RETURN_INT32((int32) ((uint8) a) - (int32) ((uint8) b));
 230 }
 231
 232 Datum
 233 btnamecmp(PG_FUNCTION_ARGS)
 234 {
 235         Name            a = PG_GETARG_NAME(0);
 236         Name            b = PG_GETARG_NAME(1);
 237
 238         PG_RETURN_INT32(strncmp(NameStr(*a), NameStr(*b), NAMEDATALEN));
 239 }