This adds 3 new variants of the random() function:
random(min integer, max integer) returns integer
random(min bigint, max bigint) returns bigint
random(min numeric, max numeric) returns numeric
Each returns a random number x in the range min <= x <= max.
For the numeric function, the number of digits after the decimal point
is equal to the number of digits that "min" or "max" has after the
decimal point, whichever has more.
The main entry points for these functions are in a new C source file.
The existing random(), random_normal(), and setseed() functions are
moved there too, so that they can all share the same PRNG state, which
is kept private to that file.
Dean Rasheed, reviewed by Jian He, David Zhang, Aleksander Alekseev,
and Tomas Vondra.
Discussion: https://postgr.es/m/CAEZATCV89Vxuq93xQdmc0t-0Y2zeeNQTdsjbmV7dyFBPykbV4Q@mail.gmail.com
Expose the standard error functions as SQL-callable functions. These
are expected to be useful to people working with normal distributions,
and we use them here to test the distribution from random_normal().
Since these functions are defined in the POSIX and C99 standards, they
should in theory be available on all supported platforms. If that
turns out not to be the case, more work will be needed.
On all platforms tested so far, using extra_float_digits = -1 in the
regression tests is sufficient to allow for variations between
implementations. However, past experience has shown that there are
almost certainly going to be additional unexpected portability issues,
so these tests may well need further adjustments, based on the
buildfarm results.
Dean Rasheed, reviewed by Nathan Bossart and Thomas Munro.
Discussion: https://postgr.es/m/CAEZATCXv5fi7+Vu-POiyai+ucF95+YMcCMafxV+eZuN1B-=MkQ@mail.gmail.com
As I suspected, some machines have even more low-order-bit
inaccuracy than the ones I tested. Tweak new test so that
(hopefully) it will pass everywhere. Per buildfarm.
Discussion: https://postgr.es/m/4173840.1673290336@sss.pgh.pa.us
We had some pretty ad-hoc and inefficient code here. To make
matters worse, it didn't test the properties of the random()
function very thoroughly, and it had a test failure rate of
one in every few tens of thousands of runs. Replace the
script altogether with new test cases that prove much more
about random()'s output, run faster, and can be calculated
to have test failure rates on the order of 1e-9.
Having done that, the failure rate of this script should be
negligible in comparison to other causes of test failures,
so remove the "ignore" marker for it in parallel_schedule.
(If it does fail, we'd like to know about that, so "ignore"
was always pretty counterproductive.)
Tom Lane and Dean Rasheed
Discussion: https://postgr.es/m/4173840.1673290336@sss.pgh.pa.us
CREATE TABLE AS has been preferred over SELECT INTO (outside of ecpg
and PL/pgSQL) for a long time. There were still a few uses of SELECT
INTO in tests and documentation, some old, some more recent. This
changes them to CREATE TABLE AS. Some occurrences in the tests remain
where they are specifically testing SELECT INTO parsing or similar.
Discussion: https://www.postgresql.org/message-id/flat/96dc0df3-e13a-a85d-d045-d6e2c85218da%40enterprisedb.com
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
Dean Rasheed
Tom Lane
Peter Eisentraut
Bruce Momjian
Thomas G. Lockhart