1 /*-------------------------------------------------------------------------
2 *
3 * xid.c
4 * POSTGRES transaction identifier and command identifier datatypes.
5 *
6 * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
7 * Portions Copyright (c) 1994, Regents of the University of California
8 *
9 *
10 * IDENTIFICATION
11 * src/backend/utils/adt/xid.c
12 *
13 *-------------------------------------------------------------------------
14 */
15 #include "postgres.h"
16
17 #include <limits.h>
18
19 #include "access/multixact.h"
20 #include "access/transam.h"
21 #include "access/xact.h"
22 #include "libpq/pqformat.h"
23 #include "utils/builtins.h"
24
25 #define PG_GETARG_TRANSACTIONID(n) DatumGetTransactionId(PG_GETARG_DATUM(n))
26 #define PG_RETURN_TRANSACTIONID(x) return TransactionIdGetDatum(x)
27
28 #define PG_GETARG_COMMANDID(n) DatumGetCommandId(PG_GETARG_DATUM(n))
29 #define PG_RETURN_COMMANDID(x) return CommandIdGetDatum(x)
30
31
32 Datum
xidin(PG_FUNCTION_ARGS)33 xidin(PG_FUNCTION_ARGS)
34 {
35 char *str = PG_GETARG_CSTRING(0);
36
37 PG_RETURN_TRANSACTIONID((TransactionId) strtoul(str, NULL, 0));
38 }
39
40 Datum
xidout(PG_FUNCTION_ARGS)41 xidout(PG_FUNCTION_ARGS)
42 {
43 TransactionId transactionId = PG_GETARG_TRANSACTIONID(0);
44 char *result = (char *) palloc(16);
45
46 snprintf(result, 16, "%lu", (unsigned long) transactionId);
47 PG_RETURN_CSTRING(result);
48 }
49
50 /*
51 * xidrecv - converts external binary format to xid
52 */
53 Datum
xidrecv(PG_FUNCTION_ARGS)54 xidrecv(PG_FUNCTION_ARGS)
55 {
56 StringInfo buf = (StringInfo) PG_GETARG_POINTER(0);
57
58 PG_RETURN_TRANSACTIONID((TransactionId) pq_getmsgint(buf, sizeof(TransactionId)));
59 }
60
61 /*
62 * xidsend - converts xid to binary format
63 */
64 Datum
xidsend(PG_FUNCTION_ARGS)65 xidsend(PG_FUNCTION_ARGS)
66 {
67 TransactionId arg1 = PG_GETARG_TRANSACTIONID(0);
68 StringInfoData buf;
69
70 pq_begintypsend(&buf);
71 pq_sendint32(&buf, arg1);
72 PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
73 }
74
75 /*
76 * xideq - are two xids equal?
77 */
78 Datum
xideq(PG_FUNCTION_ARGS)79 xideq(PG_FUNCTION_ARGS)
80 {
81 TransactionId xid1 = PG_GETARG_TRANSACTIONID(0);
82 TransactionId xid2 = PG_GETARG_TRANSACTIONID(1);
83
84 PG_RETURN_BOOL(TransactionIdEquals(xid1, xid2));
85 }
86
87 /*
88 * xidneq - are two xids different?
89 */
90 Datum
xidneq(PG_FUNCTION_ARGS)91 xidneq(PG_FUNCTION_ARGS)
92 {
93 TransactionId xid1 = PG_GETARG_TRANSACTIONID(0);
94 TransactionId xid2 = PG_GETARG_TRANSACTIONID(1);
95
96 PG_RETURN_BOOL(!TransactionIdEquals(xid1, xid2));
97 }
98
99 /*
100 * xid_age - compute age of an XID (relative to latest stable xid)
101 */
102 Datum
xid_age(PG_FUNCTION_ARGS)103 xid_age(PG_FUNCTION_ARGS)
104 {
105 TransactionId xid = PG_GETARG_TRANSACTIONID(0);
106 TransactionId now = GetStableLatestTransactionId();
107
108 /* Permanent XIDs are always infinitely old */
109 if (!TransactionIdIsNormal(xid))
110 PG_RETURN_INT32(INT_MAX);
111
112 PG_RETURN_INT32((int32) (now - xid));
113 }
114
115 /*
116 * mxid_age - compute age of a multi XID (relative to latest stable mxid)
117 */
118 Datum
mxid_age(PG_FUNCTION_ARGS)119 mxid_age(PG_FUNCTION_ARGS)
120 {
121 TransactionId xid = PG_GETARG_TRANSACTIONID(0);
122 MultiXactId now = ReadNextMultiXactId();
123
124 if (!MultiXactIdIsValid(xid))
125 PG_RETURN_INT32(INT_MAX);
126
127 PG_RETURN_INT32((int32) (now - xid));
128 }
129
130 /*
131 * xidComparator
132 * qsort comparison function for XIDs
133 *
134 * We can't use wraparound comparison for XIDs because that does not respect
135 * the triangle inequality! Any old sort order will do.
136 */
137 int
xidComparator(const void * arg1,const void * arg2)138 xidComparator(const void *arg1, const void *arg2)
139 {
140 TransactionId xid1 = *(const TransactionId *) arg1;
141 TransactionId xid2 = *(const TransactionId *) arg2;
142
143 if (xid1 > xid2)
144 return 1;
145 if (xid1 < xid2)
146 return -1;
147 return 0;
148 }
149
150 /*****************************************************************************
151 * COMMAND IDENTIFIER ROUTINES *
152 *****************************************************************************/
153
154 /*
155 * cidin - converts CommandId to internal representation.
156 */
157 Datum
cidin(PG_FUNCTION_ARGS)158 cidin(PG_FUNCTION_ARGS)
159 {
160 char *str = PG_GETARG_CSTRING(0);
161
162 PG_RETURN_COMMANDID((CommandId) strtoul(str, NULL, 0));
163 }
164
165 /*
166 * cidout - converts a cid to external representation.
167 */
168 Datum
cidout(PG_FUNCTION_ARGS)169 cidout(PG_FUNCTION_ARGS)
170 {
171 CommandId c = PG_GETARG_COMMANDID(0);
172 char *result = (char *) palloc(16);
173
174 snprintf(result, 16, "%lu", (unsigned long) c);
175 PG_RETURN_CSTRING(result);
176 }
177
178 /*
179 * cidrecv - converts external binary format to cid
180 */
181 Datum
cidrecv(PG_FUNCTION_ARGS)182 cidrecv(PG_FUNCTION_ARGS)
183 {
184 StringInfo buf = (StringInfo) PG_GETARG_POINTER(0);
185
186 PG_RETURN_COMMANDID((CommandId) pq_getmsgint(buf, sizeof(CommandId)));
187 }
188
189 /*
190 * cidsend - converts cid to binary format
191 */
192 Datum
cidsend(PG_FUNCTION_ARGS)193 cidsend(PG_FUNCTION_ARGS)
194 {
195 CommandId arg1 = PG_GETARG_COMMANDID(0);
196 StringInfoData buf;
197
198 pq_begintypsend(&buf);
199 pq_sendint32(&buf, arg1);
200 PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
201 }
202
203 Datum
cideq(PG_FUNCTION_ARGS)204 cideq(PG_FUNCTION_ARGS)
205 {
206 CommandId arg1 = PG_GETARG_COMMANDID(0);
207 CommandId arg2 = PG_GETARG_COMMANDID(1);
208
209 PG_RETURN_BOOL(arg1 == arg2);
210 }
211