1/*-------------------------------------------------------------------------
2 *
3 * nbtcompare.c
4 * Comparison functions for btree access method.
5 *
6 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
7 * Portions Copyright (c) 1994, Regents of the University of California
8 *
9 *
10 * IDENTIFICATION
11 * src/backend/access/nbtree/nbtcompare.c
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 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.
29 *
30 * NOTE: it is critical that the comparison function impose a total order
31 * on all non-NULL values of the data type, and that the datatype's
32 * boolean comparison operators (= < >= etc) yield results consistent
33 * with the comparison routine. Otherwise bad behavior may ensue.
34 * (For example, the comparison operators must NOT punt when faced with
35 * NAN or other funny values; you must devise some collation sequence for
36 * all such values.) If the datatype is not trivial, this is most
37 * reliably done by having the boolean operators invoke the same
38 * three-way comparison code that the btree function does. Therefore,
39 * this file contains only btree support for "trivial" datatypes ---
40 * all others are in the /utils/adt/ files that implement their datatypes.
41 *
42 * NOTE: these routines must not leak memory, since memory allocated
43 * during an index access won't be recovered till end of query. This
44 * primarily affects comparison routines for toastable datatypes;
45 * they have to be careful to free any detoasted copy of an input datum.
46 *
47 * NOTE: we used to forbid comparison functions from returning INT_MIN,
48 * but that proves to be too error-prone because some platforms' versions
49 * of memcmp() etc can return INT_MIN. As a means of stress-testing
50 * callers, this file can be compiled with STRESS_SORT_INT_MIN defined
51 * to cause many of these functions to return INT_MIN or INT_MAX instead of
52 * their customary -1/+1. For production, though, that's not a good idea
53 * since users or third-party code might expect the traditional results.
54 *-------------------------------------------------------------------------
55 */
56#include "postgres.h"
57
58#include <limits.h>
59
60#include "utils/builtins.h"
61#include "utils/sortsupport.h"
62
63#ifdef STRESS_SORT_INT_MIN
64#define A_LESS_THAN_B INT_MIN
65#define A_GREATER_THAN_B INT_MAX
66#else
67#define A_LESS_THAN_B (-1)
68#define A_GREATER_THAN_B 1
69#endif
70
71
72Datum
73btboolcmp(PG_FUNCTION_ARGS)
74{
75 bool a = PG_GETARG_BOOL(0);
76 bool b = PG_GETARG_BOOL(1);
77
78 PG_RETURN_INT32((int32) a - (int32) b);
79}
80
81Datum
82btint2cmp(PG_FUNCTION_ARGS)
83{
84 int16 a = PG_GETARG_INT16(0);
85 int16 b = PG_GETARG_INT16(1);
86
87 PG_RETURN_INT32((int32) a - (int32) b);
88}
89
90static int
91btint2fastcmp(Datum x, Datum y, SortSupport ssup)
92{
93 int16 a = DatumGetInt16(x);
94 int16 b = DatumGetInt16(y);
95
96 return (int) a - (int) b;
97}
98
99Datum
100btint2sortsupport(PG_FUNCTION_ARGS)
101{
102 SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);
103
104 ssup->comparator = btint2fastcmp;
105 PG_RETURN_VOID();
106}
107
108Datum
109btint4cmp(PG_FUNCTION_ARGS)
110{
111 int32 a = PG_GETARG_INT32(0);
112 int32 b = PG_GETARG_INT32(1);
113
114 if (a > b)
115 PG_RETURN_INT32(A_GREATER_THAN_B);
116 else if (a == b)
117 PG_RETURN_INT32(0);
118 else
119 PG_RETURN_INT32(A_LESS_THAN_B);
120}
121
122static int
123btint4fastcmp(Datum x, Datum y, SortSupport ssup)
124{
125 int32 a = DatumGetInt32(x);
126 int32 b = DatumGetInt32(y);
127
128 if (a > b)
129 return A_GREATER_THAN_B;
130 else if (a == b)
131 return 0;
132 else
133 return A_LESS_THAN_B;
134}
135
136Datum
137btint4sortsupport(PG_FUNCTION_ARGS)
138{
139 SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);
140
141 ssup->comparator = btint4fastcmp;
142 PG_RETURN_VOID();
143}
144
145Datum
146btint8cmp(PG_FUNCTION_ARGS)
147{
148 int64 a = PG_GETARG_INT64(0);
149 int64 b = PG_GETARG_INT64(1);
150
151 if (a > b)
152 PG_RETURN_INT32(A_GREATER_THAN_B);
153 else if (a == b)
154 PG_RETURN_INT32(0);
155 else
156 PG_RETURN_INT32(A_LESS_THAN_B);
157}
158
159static int
160btint8fastcmp(Datum x, Datum y, SortSupport ssup)
161{
162 int64 a = DatumGetInt64(x);
163 int64 b = DatumGetInt64(y);
164
165 if (a > b)
166 return A_GREATER_THAN_B;
167 else if (a == b)
168 return 0;
169 else
170 return A_LESS_THAN_B;
171}
172
173Datum
174btint8sortsupport(PG_FUNCTION_ARGS)
175{
176 SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);
177
178 ssup->comparator = btint8fastcmp;
179 PG_RETURN_VOID();
180}
181
182Datum
183btint48cmp(PG_FUNCTION_ARGS)
184{
185 int32 a = PG_GETARG_INT32(0);
186 int64 b = PG_GETARG_INT64(1);
187
188 if (a > b)
189 PG_RETURN_INT32(A_GREATER_THAN_B);
190 else if (a == b)
191 PG_RETURN_INT32(0);
192 else
193 PG_RETURN_INT32(A_LESS_THAN_B);
194}
195
196Datum
197btint84cmp(PG_FUNCTION_ARGS)
198{
199 int64 a = PG_GETARG_INT64(0);
200 int32 b = PG_GETARG_INT32(1);
201
202 if (a > b)
203 PG_RETURN_INT32(A_GREATER_THAN_B);
204 else if (a == b)
205 PG_RETURN_INT32(0);
206 else
207 PG_RETURN_INT32(A_LESS_THAN_B);
208}
209
210Datum
211btint24cmp(PG_FUNCTION_ARGS)
212{
213 int16 a = PG_GETARG_INT16(0);
214 int32 b = PG_GETARG_INT32(1);
215
216 if (a > b)
217 PG_RETURN_INT32(A_GREATER_THAN_B);
218 else if (a == b)
219 PG_RETURN_INT32(0);
220 else
221 PG_RETURN_INT32(A_LESS_THAN_B);
222}
223
224Datum
225btint42cmp(PG_FUNCTION_ARGS)
226{
227 int32 a = PG_GETARG_INT32(0);
228 int16 b = PG_GETARG_INT16(1);
229
230 if (a > b)
231 PG_RETURN_INT32(A_GREATER_THAN_B);
232 else if (a == b)
233 PG_RETURN_INT32(0);
234 else
235 PG_RETURN_INT32(A_LESS_THAN_B);
236}
237
238Datum
239btint28cmp(PG_FUNCTION_ARGS)
240{
241 int16 a = PG_GETARG_INT16(0);
242 int64 b = PG_GETARG_INT64(1);
243
244 if (a > b)
245 PG_RETURN_INT32(A_GREATER_THAN_B);
246 else if (a == b)
247 PG_RETURN_INT32(0);
248 else
249 PG_RETURN_INT32(A_LESS_THAN_B);
250}
251
252Datum
253btint82cmp(PG_FUNCTION_ARGS)
254{
255 int64 a = PG_GETARG_INT64(0);
256 int16 b = PG_GETARG_INT16(1);
257
258 if (a > b)
259 PG_RETURN_INT32(A_GREATER_THAN_B);
260 else if (a == b)
261 PG_RETURN_INT32(0);
262 else
263 PG_RETURN_INT32(A_LESS_THAN_B);
264}
265
266Datum
267btoidcmp(PG_FUNCTION_ARGS)
268{
269 Oid a = PG_GETARG_OID(0);
270 Oid b = PG_GETARG_OID(1);
271
272 if (a > b)
273 PG_RETURN_INT32(A_GREATER_THAN_B);
274 else if (a == b)
275 PG_RETURN_INT32(0);
276 else
277 PG_RETURN_INT32(A_LESS_THAN_B);
278}
279
280static int
281btoidfastcmp(Datum x, Datum y, SortSupport ssup)
282{
283 Oid a = DatumGetObjectId(x);
284 Oid b = DatumGetObjectId(y);
285
286 if (a > b)
287 return A_GREATER_THAN_B;
288 else if (a == b)
289 return 0;
290 else
291 return A_LESS_THAN_B;
292}
293
294Datum
295btoidsortsupport(PG_FUNCTION_ARGS)
296{
297 SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);
298
299 ssup->comparator = btoidfastcmp;
300 PG_RETURN_VOID();
301}
302
303Datum
304btoidvectorcmp(PG_FUNCTION_ARGS)
305{
306 oidvector *a = (oidvector *) PG_GETARG_POINTER(0);
307 oidvector *b = (oidvector *) PG_GETARG_POINTER(1);
308 int i;
309
310 /* We arbitrarily choose to sort first by vector length */
311 if (a->dim1 != b->dim1)
312 PG_RETURN_INT32(a->dim1 - b->dim1);
313
314 for (i = 0; i < a->dim1; i++)
315 {
316 if (a->values[i] != b->values[i])
317 {
318 if (a->values[i] > b->values[i])
319 PG_RETURN_INT32(A_GREATER_THAN_B);
320 else
321 PG_RETURN_INT32(A_LESS_THAN_B);
322 }
323 }
324 PG_RETURN_INT32(0);
325}
326
327Datum
328btcharcmp(PG_FUNCTION_ARGS)
329{
330 char a = PG_GETARG_CHAR(0);
331 char b = PG_GETARG_CHAR(1);
332
333 /* Be careful to compare chars as unsigned */
334 PG_RETURN_INT32((int32) ((uint8) a) - (int32) ((uint8) b));
335}
336