src/backend/utils/adt/xid.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * xid.c
   4  *        POSTGRES transaction identifier and command identifier datatypes.
   5  *
   6  * Portions Copyright (c) 1996-2011, 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/transam.h"
  20 #include "access/xact.h"
  21 #include "libpq/pqformat.h"
  22 #include "utils/builtins.h"
  23
  24 #define PG_GETARG_TRANSACTIONID(n)      DatumGetTransactionId(PG_GETARG_DATUM(n))
  25 #define PG_RETURN_TRANSACTIONID(x)      return TransactionIdGetDatum(x)
  26
  27 #define PG_GETARG_COMMANDID(n)          DatumGetCommandId(PG_GETARG_DATUM(n))
  28 #define PG_RETURN_COMMANDID(x)          return CommandIdGetDatum(x)
  29
  30
  31 Datum
  32 xidin(PG_FUNCTION_ARGS)
  33 {
  34         char       *str = PG_GETARG_CSTRING(0);
  35
  36         PG_RETURN_TRANSACTIONID((TransactionId) strtoul(str, NULL, 0));
  37 }
  38
  39 Datum
  40 xidout(PG_FUNCTION_ARGS)
  41 {
  42         TransactionId transactionId = PG_GETARG_TRANSACTIONID(0);
  43
  44         /* maximum 32 bit unsigned integer representation takes 10 chars */
  45         char       *str = palloc(11);
  46
  47         snprintf(str, 11, "%lu", (unsigned long) transactionId);
  48
  49         PG_RETURN_CSTRING(str);
  50 }
  51
  52 /*
  53  *              xidrecv                 - converts external binary format to xid
  54  */
  55 Datum
  56 xidrecv(PG_FUNCTION_ARGS)
  57 {
  58         StringInfo      buf = (StringInfo) PG_GETARG_POINTER(0);
  59
  60         PG_RETURN_TRANSACTIONID((TransactionId) pq_getmsgint(buf, sizeof(TransactionId)));
  61 }
  62
  63 /*
  64  *              xidsend                 - converts xid to binary format
  65  */
  66 Datum
  67 xidsend(PG_FUNCTION_ARGS)
  68 {
  69         TransactionId arg1 = PG_GETARG_TRANSACTIONID(0);
  70         StringInfoData buf;
  71
  72         pq_begintypsend(&buf);
  73         pq_sendint(&buf, arg1, sizeof(arg1));
  74         PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
  75 }
  76
  77 /*
  78  *              xideq                   - are two xids equal?
  79  */
  80 Datum
  81 xideq(PG_FUNCTION_ARGS)
  82 {
  83         TransactionId xid1 = PG_GETARG_TRANSACTIONID(0);
  84         TransactionId xid2 = PG_GETARG_TRANSACTIONID(1);
  85
  86         PG_RETURN_BOOL(TransactionIdEquals(xid1, xid2));
  87 }
  88
  89 /*
  90  *              xid_age                 - compute age of an XID (relative to current xact)
  91  */
  92 Datum
  93 xid_age(PG_FUNCTION_ARGS)
  94 {
  95         TransactionId xid = PG_GETARG_TRANSACTIONID(0);
  96         TransactionId now = GetTopTransactionId();
  97
  98         /* Permanent XIDs are always infinitely old */
  99         if (!TransactionIdIsNormal(xid))
 100                 PG_RETURN_INT32(INT_MAX);
 101
 102         PG_RETURN_INT32((int32) (now - xid));
 103 }
 104
 105 /*
 106  * xidComparator
 107  *              qsort comparison function for XIDs
 108  *
 109  * We can't use wraparound comparison for XIDs because that does not respect
 110  * the triangle inequality!  Any old sort order will do.
 111  */
 112 int
 113 xidComparator(const void *arg1, const void *arg2)
 114 {
 115         TransactionId xid1 = *(const TransactionId *) arg1;
 116         TransactionId xid2 = *(const TransactionId *) arg2;
 117
 118         if (xid1 > xid2)
 119                 return 1;
 120         if (xid1 < xid2)
 121                 return -1;
 122         return 0;
 123 }
 124
 125 /*****************************************************************************
 126  *       COMMAND IDENTIFIER ROUTINES                                                                                     *
 127  *****************************************************************************/
 128
 129 /*
 130  *              cidin   - converts CommandId to internal representation.
 131  */
 132 Datum
 133 cidin(PG_FUNCTION_ARGS)
 134 {
 135         char       *s = PG_GETARG_CSTRING(0);
 136         CommandId       c;
 137
 138         c = atoi(s);
 139
 140         PG_RETURN_COMMANDID(c);
 141 }
 142
 143 /*
 144  *              cidout  - converts a cid to external representation.
 145  */
 146 Datum
 147 cidout(PG_FUNCTION_ARGS)
 148 {
 149         CommandId       c = PG_GETARG_COMMANDID(0);
 150         char       *result = (char *) palloc(16);
 151
 152         snprintf(result, 16, "%u", (unsigned int) c);
 153         PG_RETURN_CSTRING(result);
 154 }
 155
 156 /*
 157  *              cidrecv                 - converts external binary format to cid
 158  */
 159 Datum
 160 cidrecv(PG_FUNCTION_ARGS)
 161 {
 162         StringInfo      buf = (StringInfo) PG_GETARG_POINTER(0);
 163
 164         PG_RETURN_COMMANDID((CommandId) pq_getmsgint(buf, sizeof(CommandId)));
 165 }
 166
 167 /*
 168  *              cidsend                 - converts cid to binary format
 169  */
 170 Datum
 171 cidsend(PG_FUNCTION_ARGS)
 172 {
 173         CommandId       arg1 = PG_GETARG_COMMANDID(0);
 174         StringInfoData buf;
 175
 176         pq_begintypsend(&buf);
 177         pq_sendint(&buf, arg1, sizeof(arg1));
 178         PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
 179 }
 180
 181 Datum
 182 cideq(PG_FUNCTION_ARGS)
 183 {
 184         CommandId       arg1 = PG_GETARG_COMMANDID(0);
 185         CommandId       arg2 = PG_GETARG_COMMANDID(1);
 186
 187         PG_RETURN_BOOL(arg1 == arg2);
 188 }