postgresql/src/backend/utils/adt/misc.c

/*-------------------------------------------------------------------------
 *
 * misc.c--
 *    
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.7 1997/07/28 00:55:58 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <sys/types.h>
#include <sys/file.h>
#include "postgres.h"
#include "utils/datum.h"
#include "catalog/pg_type.h"
#include "utils/builtins.h"

#include "port-protos.h"  /* For random(), sometimes */


/*-------------------------------------------------------------------------
 * Check if data is Null 
 */
bool
nullvalue(Datum value, bool *isNull)
{
    if (*isNull) {
	*isNull = false;
	return(true);
    }
    return(false);
    
}

/*----------------------------------------------------------------------*
 *     check if data is not Null                                        *
 *--------------------------------------------------------------------- */
bool
nonnullvalue(Datum value, bool *isNull)
{
    if (*isNull) {
	*isNull = false;
	return(false);
    }
    return(true);
    
}

/*
 * oidrand (oid o, int4 X)-
 *    takes in an oid and a int4 X, and will return 'true'
 *  about 1/X of the time.
 *    Useful for doing random sampling or subsetting.
 *  if X == 0, this will always return true;
 *
 * Example use:
 *     select * from TEMP where oidrand(TEMP.oid, 10)
 * will return about 1/10 of the tuples in TEMP
 *
 */
bool 
oidrand(Oid o, int32 X)
{
    bool result;

    if (X == 0) return true;

    result = (random() % X == 0);
    return result;
}

/*
   oidsrand(int32 X) -
      seeds the random number generator
      always return true
*/ 
bool
oidsrand(int32 X)
{
    srand(X);
    return true;
}



int32
userfntest(int i)
{
    return (i);
}