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Clean up bogosities in use of random(3) and srandom(3) --- do not assume

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that RAND_MAX applies to them, since it doesn't.  Instead add a
config.h parameter MAX_RANDOM_VALUE.  This is currently set at 2^31-1
but could be auto-configured if that ever proves necessary.  Also fix
some outright bugs like calling srand() where srandom() is appropriate.
This commit is contained in:
Tom Lane
2000-08-07 00:51:42 +00:00
parent 259489bab7
commit 9426047021
8 changed files with 47 additions and 25 deletions
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14
src/backend/utils/adt/misc.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.19 2000/06/05 07:28:52 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.20 2000/08/07 00:51:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -45,15 +45,18 @@ nonnullvalue(PG_FUNCTION_ARGS)
/*
* oidrand (oid o, int4 X)-
* takes in an oid and a int4 X, and will return 'true'
* about 1/X of the time.
* 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.
* 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
*
* 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;
@ -61,7 +64,6 @@ static bool random_initialized = false;
Datum
oidrand(PG_FUNCTION_ARGS)
{
/* XXX seems like we ought to be using the oid for something? */
#ifdef NOT_USED
Oid o = PG_GETARG_OID(0);
#endif
@ -96,7 +98,7 @@ oidsrand(PG_FUNCTION_ARGS)
{
int32 X = PG_GETARG_INT32(0);
srand(X);
srandom((unsigned int) X);
random_initialized = true;
PG_RETURN_BOOL(true);
}