From 3804539e48e794781c6145c7f988f5d507418fa8 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sun, 28 Nov 2021 21:32:36 -0500 Subject: 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 --- src/backend/access/spgist/spgdoinsert.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'src/backend/access/spgist/spgdoinsert.c') diff --git a/src/backend/access/spgist/spgdoinsert.c b/src/backend/access/spgist/spgdoinsert.c index 70557bcf3d0..e7afb2c242a 100644 --- a/src/backend/access/spgist/spgdoinsert.c +++ b/src/backend/access/spgist/spgdoinsert.c @@ -19,6 +19,7 @@ #include "access/spgist_private.h" #include "access/spgxlog.h" #include "access/xloginsert.h" +#include "common/pg_prng.h" #include "miscadmin.h" #include "storage/bufmgr.h" #include "utils/rel.h" @@ -2210,7 +2211,9 @@ spgdoinsert(Relation index, SpGistState *state, if (out.resultType == spgAddNode) elog(ERROR, "cannot add a node to an allTheSame inner tuple"); else if (out.resultType == spgMatchNode) - out.result.matchNode.nodeN = random() % innerTuple->nNodes; + out.result.matchNode.nodeN = + pg_prng_uint64_range(&pg_global_prng_state, + 0, innerTuple->nNodes - 1); } switch (out.resultType) -- cgit v1.2.3