blob: 24eb68218437ceb4e490e9efdc8f58dd34415e3b (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
|
/*-------------------------------------------------------------------------
*
* misc.c
*
*
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.25 2002/08/20 04:45:59 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include <sys/types.h>
#include <sys/file.h>
#include <time.h>
#include "postgres.h"
#include "miscadmin.h"
#include "utils/builtins.h"
/*
* Check if data is Null
*/
Datum
nullvalue(PG_FUNCTION_ARGS)
{
if (PG_ARGISNULL(0))
PG_RETURN_BOOL(true);
PG_RETURN_BOOL(false);
}
/*
* Check if data is not Null
*/
Datum
nonnullvalue(PG_FUNCTION_ARGS)
{
if (PG_ARGISNULL(0))
PG_RETURN_BOOL(false);
PG_RETURN_BOOL(true);
}
/*
* oidrand (oid o, int4 X)-
* Takes in an oid and a int4 X, and will return 'true' about 1/X of
* the time. If X == 0, this will always return true.
* Useful for doing random sampling or subsetting.
*
* Example use:
* select * from TEMP where oidrand(TEMP.oid, 10)
* will return about 1/10 of the tuples in TEMP
*
* NOTE: the OID input is not used at all. It is there just because of
* an old optimizer bug: a qual expression containing no variables was
* mistakenly assumed to be a constant. Pretending to access the row's OID
* prevented the optimizer from treating the oidrand() result as constant.
*/
static bool random_initialized = false;
Datum
oidrand(PG_FUNCTION_ARGS)
{
#ifdef NOT_USED
Oid o = PG_GETARG_OID(0);
#endif
int32 X = PG_GETARG_INT32(1);
bool result;
if (X == 0)
PG_RETURN_BOOL(true);
/*
* We do this because the cancel key is actually a random, so we don't
* want them to be able to request random numbers using our postmaster
* seeded value.
*/
if (!random_initialized)
{
srandom((unsigned int) time(NULL));
random_initialized = true;
}
result = (random() % X == 0);
PG_RETURN_BOOL(result);
}
/*
oidsrand(int32 X) -
seeds the random number generator
always returns true
*/
Datum
oidsrand(PG_FUNCTION_ARGS)
{
int32 X = PG_GETARG_INT32(0);
srandom((unsigned int) X);
random_initialized = true;
PG_RETURN_BOOL(true);
}
Datum
userfntest(PG_FUNCTION_ARGS)
{
int32 i = PG_GETARG_INT32(0);
PG_RETURN_INT32(i);
}
/*
* current_database()
* Expose the current database to the user
*/
Datum
current_database(PG_FUNCTION_ARGS)
{
Name db;
db = (Name) palloc(NAMEDATALEN);
namestrcpy(db, DatabaseName);
PG_RETURN_NAME(db);
}
|
