The windows random number of generator (a port of lrand48 in random.c)
seems a little weak. It seems to only offer about 16 bits of precision.
Maybe there is a bug in the implementation?
Merlin
observe:
esp=# select count(*) from (select distinct random() from
generate_series(1,1000000)) q;
count
-------
65559
(1 row)
esp=# select count(*) from (select distinct random() from
generate_series(1,1000000)) q;
count
-------
65558
(1 row)
esp=# select count(*) from (select distinct random() from
generate_series(1,1000000)) q;
count
-------
65572
(1 row)
esp=# select min(r), max(r), avg(r) from (select random() as r from
generate_series(1,1000000)) q;
min | max | avg
----------------------+-------------------+-------------------
4.6566128752458e-010 | 0.999984742142253 | 0.499985154491819
(1 row)
esp=# select min(r), max(r), avg(r) from (select random() as r from
generate_series(1,1000000)) q;
min | max | avg
----------------------+-------------------+------------------
4.6566128752458e-010 | 0.999984742142253 | 0.50079921773987
(1 row)
esp=#
esp=# select min(r), max(r), avg(r) from (select random() as r from
generate_series(1,1000000)) q;
min | max | avg
----------------------+-------------------+-------------------
4.6566128752458e-010 | 0.999984742142253 | 0.499613384426336
(1 row)
