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The "random" regression test uses a function called oidrand(), which

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takes two parameters, an OID x and an integer y, and returns "true" with
probability 1/y (the OID argument is ignored). This can be useful -- for
example, it can be used to select a random sampling of the rows in a
table (which is what the "random" regression test uses it for).

This patch removes that function, because it was old and messy. The old
function had the following problems:

- it was undocumented

- it was poorly named

- it was designed to workaround an optimizer bug that no longer exists
(the OID argument is to ensure that the optimizer won't optimize away
calls to the function; AFAIK marking the function as 'volatile' suffices
nowadays)

- it used a different random-number generation technique than the other
PSRNG-related functions in the backend do (it called random() like they
do, but it had its own logic for setting a set and deciding when to
reseed the RNG).

Ok, this patch removes oidrand(), oidsrand(), and userfntest(), and
improves the SGML docs a little bit (un-commenting the setseed()
documentation).

Neil Conway
This commit is contained in:
Bruce Momjian
2003-02-13 05:24:04 +00:00
parent 8195f8f042
commit 6cb1f4fe44
7 changed files with 41 additions and 115 deletions
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71
src/backend/utils/adt/misc.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.27 2002/09/04 20:31:28 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.28 2003/02/13 05:24:02 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -43,75 +43,6 @@ nonnullvalue(PG_FUNCTION_ARGS)
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