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/*-------------------------------------------------------------------------
*
* misc.c
*
*
* Portions Copyright (c) 1996-2001, 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 1.22 2001/03/22 03:59:51 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include <sys/types.h>
#include <sys/file.h>
#include <time.h>
#include "postgres.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);
}
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