diff options
| author | Tom Lane <tgl@sss.pgh.pa.us> | 2021-11-28 21:32:36 -0500 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2021-11-28 21:33:07 -0500 |
| commit | 3804539e48e794781c6145c7f988f5d507418fa8 (patch) | |
| tree | 317904b43ca8c1d510b23cb8fdd7b05a75e971bc /src/backend/lib | |
| parent | f44ceb46ec2d8da48f6e145bf462d5620c25e079 (diff) | |
| download | postgresql-3804539e48e794781c6145c7f988f5d507418fa8.tar.gz postgresql-3804539e48e794781c6145c7f988f5d507418fa8.zip | |
Replace random(), pg_erand48(), etc with a better PRNG API and algorithm.
Standardize on xoroshiro128** as our basic PRNG algorithm, eliminating
a bunch of platform dependencies as well as fundamentally-obsolete PRNG
code. In addition, this API replacement will ease replacing the
algorithm again in future, should that become necessary.
xoroshiro128** is a few percent slower than the drand48 family,
but it can produce full-width 64-bit random values not only 48-bit,
and it should be much more trustworthy. It's likely to be noticeably
faster than the platform's random(), depending on which platform you
are thinking about; and we can have non-global state vectors easily,
unlike with random(). It is not cryptographically strong, but neither
are the functions it replaces.
Fabien Coelho, reviewed by Dean Rasheed, Aleksander Alekseev, and myself
Discussion: https://postgr.es/m/alpine.DEB.2.22.394.2105241211230.165418@pseudo
Diffstat (limited to 'src/backend/lib')
| -rw-r--r-- | src/backend/lib/bloomfilter.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/src/backend/lib/bloomfilter.c b/src/backend/lib/bloomfilter.c index daf2c40ebf5..ac6001b712d 100644 --- a/src/backend/lib/bloomfilter.c +++ b/src/backend/lib/bloomfilter.c @@ -81,8 +81,7 @@ static inline uint32 mod_m(uint32 a, uint64 m); * distinct seed value on every call makes it unlikely that the same false * positives will reoccur when the same set is fingerprinted a second time. * Callers that don't care about this pass a constant as their seed, typically - * 0. Callers can use a pseudo-random seed in the range of 0 - INT_MAX by - * calling random(). + * 0. Callers can also use a pseudo-random seed, eg from pg_prng_uint64(). */ bloom_filter * bloom_create(int64 total_elems, int bloom_work_mem, uint64 seed) |