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| 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/executor | |
| 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/executor')
| -rw-r--r-- | src/backend/executor/nodeSamplescan.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c index 44232d50d0a..33b6fb13778 100644 --- a/src/backend/executor/nodeSamplescan.c +++ b/src/backend/executor/nodeSamplescan.c @@ -17,6 +17,7 @@ #include "access/relscan.h" #include "access/tableam.h" #include "access/tsmapi.h" +#include "common/pg_prng.h" #include "executor/executor.h" #include "executor/nodeSamplescan.h" #include "miscadmin.h" @@ -154,7 +155,7 @@ ExecInitSampleScan(SampleScan *node, EState *estate, int eflags) * do this just once, since the seed shouldn't change over rescans. */ if (tsc->repeatable == NULL) - scanstate->seed = random(); + scanstate->seed = pg_prng_uint32(&pg_global_prng_state); /* * Finally, initialize the TABLESAMPLE method handler. |