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

configure

@@ -16463,32 +16463,6 @@ esac
 
 fi
 
-ac_fn_c_check_func "$LINENO" "random" "ac_cv_func_random"
-if test "x$ac_cv_func_random" = xyes; then :
-  $as_echo "#define HAVE_RANDOM 1" >>confdefs.h
-
-else
-  case " $LIBOBJS " in
-  *" random.$ac_objext "* ) ;;
-  *) LIBOBJS="$LIBOBJS random.$ac_objext"
- ;;
-esac
-
-fi
-
-ac_fn_c_check_func "$LINENO" "srandom" "ac_cv_func_srandom"
-if test "x$ac_cv_func_srandom" = xyes; then :
-  $as_echo "#define HAVE_SRANDOM 1" >>confdefs.h
-
-else
-  case " $LIBOBJS " in
-  *" srandom.$ac_objext "* ) ;;
-  *) LIBOBJS="$LIBOBJS srandom.$ac_objext"
- ;;
-esac
-
-fi
-
 ac_fn_c_check_func "$LINENO" "strlcat" "ac_cv_func_strlcat"
 if test "x$ac_cv_func_strlcat" = xyes; then :
   $as_echo "#define HAVE_STRLCAT 1" >>confdefs.h

configure.ac

@@ -1858,8 +1858,6 @@ AC_REPLACE_FUNCS(m4_normalize([
 	mkdtemp
 	pread
 	pwrite
-	random
-	srandom
 	strlcat
 	strlcpy
 	strnlen

contrib/amcheck/verify_nbtree.c

@@ -32,6 +32,7 @@
 #include "catalog/index.h"
 #include "catalog/pg_am.h"
 #include "commands/tablecmds.h"
+#include "common/pg_prng.h"
 #include "lib/bloomfilter.h"
 #include "miscadmin.h"
 #include "storage/lmgr.h"
@@ -466,8 +467,8 @@ bt_check_every_level(Relation rel, Relation heaprel, bool heapkeyspace,
 		total_pages = RelationGetNumberOfBlocks(rel);
 		total_elems = Max(total_pages * (MaxTIDsPerBTreePage / 3),
 						  (int64) state->rel->rd_rel->reltuples);
-		/* Random seed relies on backend srandom() call to avoid repetition */
+		/* Generate a random seed to avoid repetition */
-		seed = random();
+		seed = pg_prng_uint64(&pg_global_prng_state);
 		/* Create Bloom filter to fingerprint index */
 		state->filter = bloom_create(total_elems, maintenance_work_mem, seed);
 		state->heaptuplespresent = 0;

contrib/auto_explain/auto_explain.c

@@ -16,6 +16,7 @@
 
 #include "access/parallel.h"
 #include "commands/explain.h"
+#include "common/pg_prng.h"
 #include "executor/instrument.h"
 #include "jit/jit.h"
 #include "utils/guc.h"
@@ -275,8 +276,7 @@ explain_ExecutorStart(QueryDesc *queryDesc, int eflags)
 	if (nesting_level == 0)
 	{
 		if (auto_explain_log_min_duration >= 0 && !IsParallelWorker())
-			current_query_sampled = (random() < auto_explain_sample_rate *
+			current_query_sampled = (pg_prng_double(&pg_global_prng_state) < auto_explain_sample_rate);
-									 ((double) MAX_RANDOM_VALUE + 1));
 		else
 			current_query_sampled = false;
 	}

contrib/file_fdw/file_fdw.c

@@ -1188,7 +1188,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
+				int			k = (int) (targrows * sampler_random_fract(&rstate.randstate));
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);

contrib/postgres_fdw/postgres_fdw.c

@@ -5158,7 +5158,7 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * sampler_random_fract(astate->rstate.randstate));
+			pos = (int) (targrows * sampler_random_fract(&astate->rstate.randstate));
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}

contrib/tablefunc/tablefunc.c

@@ -36,6 +36,7 @@
 
 #include "access/htup_details.h"
 #include "catalog/pg_type.h"
+#include "common/pg_prng.h"
 #include "executor/spi.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
@@ -290,8 +291,8 @@ get_normal_pair(float8 *x1, float8 *x2)
 
 	do
 	{
-		u1 = (float8) random() / (float8) MAX_RANDOM_VALUE;
+		u1 = pg_prng_double(&pg_global_prng_state);
-		u2 = (float8) random() / (float8) MAX_RANDOM_VALUE;
+		u2 = pg_prng_double(&pg_global_prng_state);
 
 		v1 = (2.0 * u1) - 1.0;
 		v2 = (2.0 * u2) - 1.0;

contrib/tsm_system_rows/tsm_system_rows.c

@@ -69,7 +69,7 @@ static BlockNumber system_rows_nextsampleblock(SampleScanState *node, BlockNumbe
 static OffsetNumber system_rows_nextsampletuple(SampleScanState *node,
 												BlockNumber blockno,
 												OffsetNumber maxoffset);
-static uint32 random_relative_prime(uint32 n, SamplerRandomState randstate);
+static uint32 random_relative_prime(uint32 n, pg_prng_state *randstate);
 
 
 /*
@@ -213,25 +213,25 @@ system_rows_nextsampleblock(SampleScanState *node, BlockNumber nblocks)
 		if (sampler->step == 0)
 		{
 			/* Initialize now that we have scan descriptor */
-			SamplerRandomState randstate;
+			pg_prng_state randstate;
 
 			/* If relation is empty, there's nothing to scan */
 			if (nblocks == 0)
 				return InvalidBlockNumber;
 
 			/* We only need an RNG during this setup step */
-			sampler_random_init_state(sampler->seed, randstate);
+			sampler_random_init_state(sampler->seed, &randstate);
 
 			/* Compute nblocks/firstblock/step only once per query */
 			sampler->nblocks = nblocks;
 
 			/* Choose random starting block within the relation */
 			/* (Actually this is the predecessor of the first block visited) */
-			sampler->firstblock = sampler_random_fract(randstate) *
+			sampler->firstblock = sampler_random_fract(&randstate) *
 				sampler->nblocks;
 
 			/* Find relative prime as step size for linear probing */
-			sampler->step = random_relative_prime(sampler->nblocks, randstate);
+			sampler->step = random_relative_prime(sampler->nblocks, &randstate);
 		}
 
 		/* Reinitialize lb */
@@ -317,7 +317,7 @@ gcd(uint32 a, uint32 b)
  * (else return 1).
  */
 static uint32
-random_relative_prime(uint32 n, SamplerRandomState randstate)
+random_relative_prime(uint32 n, pg_prng_state *randstate)
 {
 	uint32		r;
 

contrib/tsm_system_time/tsm_system_time.c

@@ -69,7 +69,7 @@ static BlockNumber system_time_nextsampleblock(SampleScanState *node, BlockNumbe
 static OffsetNumber system_time_nextsampletuple(SampleScanState *node,
 												BlockNumber blockno,
 												OffsetNumber maxoffset);
-static uint32 random_relative_prime(uint32 n, SamplerRandomState randstate);
+static uint32 random_relative_prime(uint32 n, pg_prng_state *randstate);
 
 
 /*
@@ -224,25 +224,25 @@ system_time_nextsampleblock(SampleScanState *node, BlockNumber nblocks)
 		if (sampler->step == 0)
 		{
 			/* Initialize now that we have scan descriptor */
-			SamplerRandomState randstate;
+			pg_prng_state randstate;
 
 			/* If relation is empty, there's nothing to scan */
 			if (nblocks == 0)
 				return InvalidBlockNumber;
 
 			/* We only need an RNG during this setup step */
-			sampler_random_init_state(sampler->seed, randstate);
+			sampler_random_init_state(sampler->seed, &randstate);
 
 			/* Compute nblocks/firstblock/step only once per query */
 			sampler->nblocks = nblocks;
 
 			/* Choose random starting block within the relation */
 			/* (Actually this is the predecessor of the first block visited) */
-			sampler->firstblock = sampler_random_fract(randstate) *
+			sampler->firstblock = sampler_random_fract(&randstate) *
 				sampler->nblocks;
 
 			/* Find relative prime as step size for linear probing */
-			sampler->step = random_relative_prime(sampler->nblocks, randstate);
+			sampler->step = random_relative_prime(sampler->nblocks, &randstate);
 		}
 
 		/* Reinitialize lb and start_time */
@@ -330,7 +330,7 @@ gcd(uint32 a, uint32 b)
  * (else return 1).
  */
 static uint32
-random_relative_prime(uint32 n, SamplerRandomState randstate)
+random_relative_prime(uint32 n, pg_prng_state *randstate)
 {
 	uint32		r;
 

src/backend/access/gin/ginget.c

@@ -16,6 +16,7 @@
 
 #include "access/gin_private.h"
 #include "access/relscan.h"
+#include "common/pg_prng.h"
 #include "miscadmin.h"
 #include "storage/predicate.h"
 #include "utils/datum.h"
@@ -787,7 +788,7 @@ entryLoadMoreItems(GinState *ginstate, GinScanEntry entry,
 	}
 }
 
-#define gin_rand() (((double) random()) / ((double) MAX_RANDOM_VALUE))
+#define gin_rand() pg_prng_double(&pg_global_prng_state)
 #define dropItem(e) ( gin_rand() > ((double)GinFuzzySearchLimit)/((double)((e)->predictNumberResult)) )
 
 /*

src/backend/access/gist/gistutil.c

@@ -19,6 +19,7 @@
 #include "access/htup_details.h"
 #include "access/reloptions.h"
 #include "catalog/pg_opclass.h"
+#include "common/pg_prng.h"
 #include "storage/indexfsm.h"
 #include "storage/lmgr.h"
 #include "utils/float.h"
@@ -507,7 +508,7 @@ gistchoose(Relation r, Page p, IndexTuple it,	/* it has compressed entry */
 			if (keep_current_best == -1)
 			{
 				/* we didn't make the random choice yet for this old best */
-				keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
+				keep_current_best = pg_prng_bool(&pg_global_prng_state) ? 1 : 0;
 			}
 			if (keep_current_best == 0)
 			{
@@ -529,7 +530,7 @@ gistchoose(Relation r, Page p, IndexTuple it,	/* it has compressed entry */
 			if (keep_current_best == -1)
 			{
 				/* we didn't make the random choice yet for this old best */
-				keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
+				keep_current_best = pg_prng_bool(&pg_global_prng_state) ? 1 : 0;
 			}
 			if (keep_current_best == 1)
 				break;

src/backend/access/nbtree/nbtinsert.c

@@ -19,6 +19,7 @@
 #include "access/nbtxlog.h"
 #include "access/transam.h"
 #include "access/xloginsert.h"
+#include "common/pg_prng.h"
 #include "lib/qunique.h"
 #include "miscadmin.h"
 #include "storage/lmgr.h"
@@ -965,7 +966,7 @@ _bt_findinsertloc(Relation rel,
 
 			if (P_RIGHTMOST(opaque) ||
 				_bt_compare(rel, itup_key, page, P_HIKEY) != 0 ||
-				random() <= (MAX_RANDOM_VALUE / 100))
+				pg_prng_uint32(&pg_global_prng_state) <= (PG_UINT32_MAX / 100))
 				break;
 
 			_bt_stepright(rel, insertstate, stack);

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)

src/backend/access/transam/xact.c

@@ -37,6 +37,7 @@
 #include "commands/async.h"
 #include "commands/tablecmds.h"
 #include "commands/trigger.h"
+#include "common/pg_prng.h"
 #include "executor/spi.h"
 #include "libpq/be-fsstubs.h"
 #include "libpq/pqsignal.h"
@@ -1990,7 +1991,7 @@ StartTransaction(void)
 	/* Determine if statements are logged in this transaction */
 	xact_is_sampled = log_xact_sample_rate != 0 &&
 		(log_xact_sample_rate == 1 ||
-		 random() <= log_xact_sample_rate * MAX_RANDOM_VALUE);
+		 pg_prng_double(&pg_global_prng_state) <= log_xact_sample_rate);
 
 	/*
 	 * initialize current transaction state fields

src/backend/commands/analyze.c

@@ -38,6 +38,7 @@
 #include "commands/progress.h"
 #include "commands/tablecmds.h"
 #include "commands/vacuum.h"
+#include "common/pg_prng.h"
 #include "executor/executor.h"
 #include "foreign/fdwapi.h"
 #include "miscadmin.h"
@@ -1140,7 +1141,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 	double		liverows = 0;	/* # live rows seen */
 	double		deadrows = 0;	/* # dead rows seen */
 	double		rowstoskip = -1;	/* -1 means not set yet */
-	long		randseed;		/* Seed for block sampler(s) */
+	uint32		randseed;		/* Seed for block sampler(s) */
 	BlockNumber totalblocks;
 	TransactionId OldestXmin;
 	BlockSamplerData bs;
@@ -1162,7 +1163,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 	OldestXmin = GetOldestNonRemovableTransactionId(onerel);
 
 	/* Prepare for sampling block numbers */
-	randseed = random();
+	randseed = pg_prng_uint32(&pg_global_prng_state);
 	nblocks = BlockSampler_Init(&bs, totalblocks, targrows, randseed);
 
 #ifdef USE_PREFETCH
@@ -1279,7 +1280,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 					 * Found a suitable tuple, so save it, replacing one old
 					 * tuple at random
 					 */
-					int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
+					int			k = (int) (targrows * sampler_random_fract(&rstate.randstate));
 
 					Assert(k >= 0 && k < targrows);
 					heap_freetuple(rows[k]);

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.

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
+ * 0.  Callers can also use a pseudo-random seed, eg from pg_prng_uint64().
- * calling random().
  */
 bloom_filter *
 bloom_create(int64 total_elems, int bloom_work_mem, uint64 seed)

src/backend/optimizer/geqo/geqo_random.c

@@ -21,14 +21,7 @@ geqo_set_seed(PlannerInfo *root, double seed)
 {
 	GeqoPrivateData *private = (GeqoPrivateData *) root->join_search_private;
 
-	/*
+	pg_prng_fseed(&private->random_state, seed);
-	 * XXX. This seeding algorithm could certainly be improved - but it is not
-	 * critical to do so.
-	 */
-	memset(private->random_state, 0, sizeof(private->random_state));
-	memcpy(private->random_state,
-		   &seed,
-		   Min(sizeof(private->random_state), sizeof(seed)));
 }
 
 double
@@ -36,5 +29,17 @@ geqo_rand(PlannerInfo *root)
 {
 	GeqoPrivateData *private = (GeqoPrivateData *) root->join_search_private;
 
-	return pg_erand48(private->random_state);
+	return pg_prng_double(&private->random_state);
+}
+
+int
+geqo_randint(PlannerInfo *root, int upper, int lower)
+{
+	GeqoPrivateData *private = (GeqoPrivateData *) root->join_search_private;
+
+	/*
+	 * In current usage, "lower" is never negative so we can just use
+	 * pg_prng_uint64_range directly.
+	 */
+	return (int) pg_prng_uint64_range(&private->random_state, lower, upper);
 }

src/backend/optimizer/geqo/geqo_selection.c

@@ -63,10 +63,6 @@ geqo_selection(PlannerInfo *root, Chromosome *momma, Chromosome *daddy,
 	/*
 	 * Ensure we have selected different genes, except if pool size is only
 	 * one, when we can't.
-	 *
-	 * This code was observed to hang up in an infinite loop when the
-	 * platform's implementation of erand48() was broken.  We now always use
-	 * our own version.
 	 */
 	if (pool->size > 1)
 	{
@@ -95,11 +91,11 @@ linear_rand(PlannerInfo *root, int pool_size, double bias)
 	double		max = (double) pool_size;
 
 	/*
-	 * If geqo_rand() returns exactly 1.0 then we will get exactly max from
+	 * geqo_rand() is not supposed to return 1.0, but if it does then we will
-	 * this equation, whereas we need 0 <= index < max.  Also it seems
+	 * get exactly max from this equation, whereas we need 0 <= index < max.
-	 * possible that roundoff error might deliver values slightly outside the
+	 * Also it seems possible that roundoff error might deliver values
-	 * range; in particular avoid passing a value slightly less than 0 to
+	 * slightly outside the range; in particular avoid passing a value
-	 * sqrt(). If we get a bad value just try again.
+	 * slightly less than 0 to sqrt().  If we get a bad value just try again.
 	 */
 	do
 	{

src/backend/postmaster/postmaster.c

@@ -98,6 +98,7 @@
 #include "catalog/pg_control.h"
 #include "common/file_perm.h"
 #include "common/ip.h"
+#include "common/pg_prng.h"
 #include "common/string.h"
 #include "lib/ilist.h"
 #include "libpq/auth.h"
@@ -2699,19 +2700,19 @@ ClosePostmasterPorts(bool am_syslogger)
 void
 InitProcessGlobals(void)
 {
-	unsigned int rseed;
-
 	MyProcPid = getpid();
 	MyStartTimestamp = GetCurrentTimestamp();
 	MyStartTime = timestamptz_to_time_t(MyStartTimestamp);
 
 	/*
-	 * Set a different seed for random() in every process.  We want something
+	 * Set a different global seed in every process.  We want something
 	 * unpredictable, so if possible, use high-quality random bits for the
 	 * seed.  Otherwise, fall back to a seed based on timestamp and PID.
 	 */
-	if (!pg_strong_random(&rseed, sizeof(rseed)))
+	if (unlikely(!pg_prng_strong_seed(&pg_global_prng_state)))
 	{
+		uint64		rseed;
+
 		/*
 		 * Since PIDs and timestamps tend to change more frequently in their
 		 * least significant bits, shift the timestamp left to allow a larger
@@ -2722,8 +2723,17 @@ InitProcessGlobals(void)
 		rseed = ((uint64) MyProcPid) ^
 			((uint64) MyStartTimestamp << 12) ^
 			((uint64) MyStartTimestamp >> 20);
+
+		pg_prng_seed(&pg_global_prng_state, rseed);
 	}
-	srandom(rseed);
+
+	/*
+	 * Also make sure that we've set a good seed for random(3).  Use of that
+	 * is deprecated in core Postgres, but extensions might use it.
+	 */
+#ifndef WIN32
+	srandom(pg_prng_uint32(&pg_global_prng_state));
+#endif
 }
 
 

src/backend/storage/file/fd.c

@@ -92,6 +92,7 @@
 #include "catalog/pg_tablespace.h"
 #include "common/file_perm.h"
 #include "common/file_utils.h"
+#include "common/pg_prng.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "port/pg_iovec.h"
@@ -2939,7 +2940,8 @@ SetTempTablespaces(Oid *tableSpaces, int numSpaces)
 	 * available tablespaces.
 	 */
 	if (numSpaces > 1)
-		nextTempTableSpace = random() % numSpaces;
+		nextTempTableSpace = pg_prng_uint64_range(&pg_global_prng_state,
+												  0, numSpaces - 1);
 	else
 		nextTempTableSpace = 0;
 }

src/backend/storage/ipc/dsm.c

@@ -33,6 +33,7 @@
 #endif
 #include <sys/stat.h>
 
+#include "common/pg_prng.h"
 #include "lib/ilist.h"
 #include "miscadmin.h"
 #include "port/pg_bitutils.h"
@@ -180,7 +181,8 @@ dsm_postmaster_startup(PGShmemHeader *shim)
 	{
 		Assert(dsm_control_address == NULL);
 		Assert(dsm_control_mapped_size == 0);
-		dsm_control_handle = random() << 1; /* Even numbers only */
+		/* Use even numbers only */
+		dsm_control_handle = pg_prng_uint32(&pg_global_prng_state) << 1;
 		if (dsm_control_handle == DSM_HANDLE_INVALID)
 			continue;
 		if (dsm_impl_op(DSM_OP_CREATE, dsm_control_handle, segsize,
@@ -536,7 +538,8 @@ dsm_create(Size size, int flags)
 		for (;;)
 		{
 			Assert(seg->mapped_address == NULL && seg->mapped_size == 0);
-			seg->handle = random() << 1;	/* Even numbers only */
+			/* Use even numbers only */
+			seg->handle = pg_prng_uint32(&pg_global_prng_state) << 1;
 			if (seg->handle == DSM_HANDLE_INVALID)	/* Reserve sentinel */
 				continue;
 			if (dsm_impl_op(DSM_OP_CREATE, seg->handle, size, &seg->impl_private,
@@ -1237,7 +1240,7 @@ make_main_region_dsm_handle(int slot)
 	 */
 	handle = 1;
 	handle |= slot << 1;
-	handle |= random() << (pg_leftmost_one_pos32(dsm_control->maxitems) + 1);
+	handle |= pg_prng_uint32(&pg_global_prng_state) << (pg_leftmost_one_pos32(dsm_control->maxitems) + 1);
 	return handle;
 }
 

src/backend/storage/lmgr/Makefile

@@ -30,9 +30,10 @@ ifdef TAS
 TASPATH = $(top_builddir)/src/backend/port/tas.o
 endif
 
-s_lock_test: s_lock.c $(top_builddir)/src/port/libpgport.a
+s_lock_test: s_lock.c $(top_builddir)/src/common/libpgcommon.a $(top_builddir)/src/port/libpgport.a
 	$(CC) $(CPPFLAGS) $(CFLAGS) -DS_LOCK_TEST=1 $(srcdir)/s_lock.c \
-		$(TASPATH) -L $(top_builddir)/src/port -lpgport -o s_lock_test
+		$(TASPATH) -L $(top_builddir)/src/common -lpgcommon \
+		-L $(top_builddir)/src/port -lpgport -o s_lock_test
 
 # see notes in src/backend/parser/Makefile
 lwlocknames.c: lwlocknames.h

src/backend/storage/lmgr/s_lock.c

@@ -50,6 +50,7 @@
 #include <time.h>
 #include <unistd.h>
 
+#include "common/pg_prng.h"
 #include "port/atomics.h"
 #include "storage/s_lock.h"
 
@@ -144,7 +145,7 @@ perform_spin_delay(SpinDelayStatus *status)
 
 		/* increase delay by a random fraction between 1X and 2X */
 		status->cur_delay += (int) (status->cur_delay *
-									((double) random() / (double) MAX_RANDOM_VALUE) + 0.5);
+									pg_prng_double(&pg_global_prng_state) + 0.5);
 		/* wrap back to minimum delay when max is exceeded */
 		if (status->cur_delay > MAX_DELAY_USEC)
 			status->cur_delay = MIN_DELAY_USEC;
@@ -303,7 +304,7 @@ volatile struct test_lock_struct test_lock;
 int
 main()
 {
-	srandom((unsigned int) time(NULL));
+	pg_prng_seed(&pg_global_prng_state, (uint64) time(NULL));
 
 	test_lock.pad1 = test_lock.pad2 = 0x44;
 

src/backend/tcop/postgres.c

@@ -42,6 +42,7 @@
 #include "catalog/pg_type.h"
 #include "commands/async.h"
 #include "commands/prepare.h"
+#include "common/pg_prng.h"
 #include "executor/spi.h"
 #include "jit/jit.h"
 #include "libpq/libpq.h"
@@ -2355,13 +2356,13 @@ check_log_duration(char *msec_str, bool was_logged)
 
 		/*
 		 * Do not log if log_statement_sample_rate = 0. Log a sample if
-		 * log_statement_sample_rate <= 1 and avoid unnecessary random() call
+		 * log_statement_sample_rate <= 1 and avoid unnecessary PRNG call if
-		 * if log_statement_sample_rate = 1.
+		 * log_statement_sample_rate = 1.
 		 */
 		if (exceeded_sample_duration)
 			in_sample = log_statement_sample_rate != 0 &&
 				(log_statement_sample_rate == 1 ||
-				 random() <= log_statement_sample_rate * MAX_RANDOM_VALUE);
+				 pg_prng_double(&pg_global_prng_state) <= log_statement_sample_rate);
 
 		if (exceeded_duration || in_sample || log_duration || xact_is_sampled)
 		{

src/backend/utils/adt/float.c

@@ -21,6 +21,7 @@
 
 #include "catalog/pg_type.h"
 #include "common/int.h"
+#include "common/pg_prng.h"
 #include "common/shortest_dec.h"
 #include "libpq/pqformat.h"
 #include "miscadmin.h"
@@ -65,7 +66,7 @@ float8		degree_c_one = 1.0;
 
 /* State for drandom() and setseed() */
 static bool drandom_seed_set = false;
-static unsigned short drandom_seed[3] = {0, 0, 0};
+static pg_prng_state drandom_seed;
 
 /* Local function prototypes */
 static double sind_q1(double x);
@@ -2762,22 +2763,20 @@ drandom(PG_FUNCTION_ARGS)
 		 * Should that fail for some reason, we fall back on a lower-quality
 		 * seed based on current time and PID.
 		 */
-		if (!pg_strong_random(drandom_seed, sizeof(drandom_seed)))
+		if (unlikely(!pg_prng_strong_seed(&drandom_seed)))
 		{
 			TimestampTz now = GetCurrentTimestamp();
 			uint64		iseed;
 
 			/* Mix the PID with the most predictable bits of the timestamp */
 			iseed = (uint64) now ^ ((uint64) MyProcPid << 32);
-			drandom_seed[0] = (unsigned short) iseed;
+			pg_prng_seed(&drandom_seed, iseed);
-			drandom_seed[1] = (unsigned short) (iseed >> 16);
-			drandom_seed[2] = (unsigned short) (iseed >> 32);
 		}
 		drandom_seed_set = true;
 	}
 
-	/* pg_erand48 produces desired result range [0.0 - 1.0) */
+	/* pg_prng_double produces desired result range [0.0 - 1.0) */
-	result = pg_erand48(drandom_seed);
+	result = pg_prng_double(&drandom_seed);
 
 	PG_RETURN_FLOAT8(result);
 }
@@ -2790,7 +2789,6 @@ Datum
 setseed(PG_FUNCTION_ARGS)
 {
 	float8		seed = PG_GETARG_FLOAT8(0);
-	uint64		iseed;
 
 	if (seed < -1 || seed > 1 || isnan(seed))
 		ereport(ERROR,
@@ -2798,11 +2796,7 @@ setseed(PG_FUNCTION_ARGS)
 				 errmsg("setseed parameter %g is out of allowed range [-1,1]",
 						seed)));
 
-	/* Use sign bit + 47 fractional bits to fill drandom_seed[] */
+	pg_prng_fseed(&drandom_seed, seed);
-	iseed = (int64) (seed * (float8) UINT64CONST(0x7FFFFFFFFFFF));
-	drandom_seed[0] = (unsigned short) iseed;
-	drandom_seed[1] = (unsigned short) (iseed >> 16);
-	drandom_seed[2] = (unsigned short) (iseed >> 32);
 	drandom_seed_set = true;
 
 	PG_RETURN_VOID();

src/backend/utils/misc/sampling.c

@@ -37,7 +37,7 @@
  */
 BlockNumber
 BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
-				  long randseed)
+				  uint32 randseed)
 {
 	bs->N = nblocks;			/* measured table size */
 
@@ -49,7 +49,7 @@ BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
 	bs->t = 0;					/* blocks scanned so far */
 	bs->m = 0;					/* blocks selected so far */
 
-	sampler_random_init_state(randseed, bs->randstate);
+	sampler_random_init_state(randseed, &bs->randstate);
 
 	return Min(bs->n, bs->N);
 }
@@ -98,7 +98,7 @@ BlockSampler_Next(BlockSampler bs)
 	 * less than k, which means that we cannot fail to select enough blocks.
 	 *----------
 	 */
-	V = sampler_random_fract(bs->randstate);
+	V = sampler_random_fract(&bs->randstate);
 	p = 1.0 - (double) k / (double) K;
 	while (V < p)
 	{
@@ -136,10 +136,11 @@ reservoir_init_selection_state(ReservoirState rs, int n)
 	 * Reservoir sampling is not used anywhere where it would need to return
 	 * repeatable results so we can initialize it randomly.
 	 */
-	sampler_random_init_state(random(), rs->randstate);
+	sampler_random_init_state(pg_prng_uint32(&pg_global_prng_state),
+							  &rs->randstate);
 
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	rs->W = exp(-log(sampler_random_fract(rs->randstate)) / n);
+	rs->W = exp(-log(sampler_random_fract(&rs->randstate)) / n);
 }
 
 double
@@ -154,7 +155,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 		double		V,
 					quot;
 
-		V = sampler_random_fract(rs->randstate);	/* Generate V */
+		V = sampler_random_fract(&rs->randstate);	/* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -186,7 +187,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 						tmp;
 
 			/* Generate U and X */
-			U = sampler_random_fract(rs->randstate);
+			U = sampler_random_fract(&rs->randstate);
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -215,7 +216,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(sampler_random_fract(rs->randstate)) / n); /* Generate W in advance */
+			W = exp(-log(sampler_random_fract(&rs->randstate)) / n);	/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
@@ -230,24 +231,22 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
  *----------
  */
 void
-sampler_random_init_state(long seed, SamplerRandomState randstate)
+sampler_random_init_state(uint32 seed, pg_prng_state *randstate)
 {
-	randstate[0] = 0x330e;		/* same as pg_erand48, but could be anything */
+	pg_prng_seed(randstate, (uint64) seed);
-	randstate[1] = (unsigned short) seed;
-	randstate[2] = (unsigned short) (seed >> 16);
 }
 
 /* Select a random value R uniformly distributed in (0 - 1) */
 double
-sampler_random_fract(SamplerRandomState randstate)
+sampler_random_fract(pg_prng_state *randstate)
 {
 	double		res;
 
-	/* pg_erand48 returns a value in [0.0 - 1.0), so we must reject 0 */
+	/* pg_prng_double returns a value in [0.0 - 1.0), so we must reject 0.0 */
 	do
 	{
-		res = pg_erand48(randstate);
+		res = pg_prng_double(randstate);
-	} while (res == 0.0);
+	} while (unlikely(res == 0.0));
 	return res;
 }
 
@@ -261,27 +260,36 @@ sampler_random_fract(SamplerRandomState randstate)
  * except that a common random state is used across all callers.
  */
 static ReservoirStateData oldrs;
+static bool oldrs_initialized = false;
 
 double
 anl_random_fract(void)
 {
 	/* initialize if first time through */
-	if (oldrs.randstate[0] == 0)
+	if (unlikely(!oldrs_initialized))
-		sampler_random_init_state(random(), oldrs.randstate);
+	{
+		sampler_random_init_state(pg_prng_uint32(&pg_global_prng_state),
+								  &oldrs.randstate);
+		oldrs_initialized = true;
+	}
 
 	/* and compute a random fraction */
-	return sampler_random_fract(oldrs.randstate);
+	return sampler_random_fract(&oldrs.randstate);
 }
 
 double
 anl_init_selection_state(int n)
 {
 	/* initialize if first time through */
-	if (oldrs.randstate[0] == 0)
+	if (unlikely(!oldrs_initialized))
-		sampler_random_init_state(random(), oldrs.randstate);
+	{
+		sampler_random_init_state(pg_prng_uint32(&pg_global_prng_state),
+								  &oldrs.randstate);
+		oldrs_initialized = true;
+	}
 
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	return exp(-log(sampler_random_fract(oldrs.randstate)) / n);
+	return exp(-log(sampler_random_fract(&oldrs.randstate)) / n);
 }
 
 double

src/bin/initdb/initdb.c

@@ -66,6 +66,7 @@
 #include "common/file_perm.h"
 #include "common/file_utils.h"
 #include "common/logging.h"
+#include "common/pg_prng.h"
 #include "common/restricted_token.h"
 #include "common/string.h"
 #include "common/username.h"
@@ -880,9 +881,10 @@ choose_dsm_implementation(void)
 {
 #ifdef HAVE_SHM_OPEN
 	int			ntries = 10;
+	pg_prng_state prng_state;
 
-	/* Initialize random(); this function is its only user in this program. */
+	/* Initialize prng; this function is its only user in this program. */
-	srandom((unsigned int) (getpid() ^ time(NULL)));
+	pg_prng_seed(&prng_state, (uint64) (getpid() ^ time(NULL)));
 
 	while (ntries > 0)
 	{
@@ -890,7 +892,7 @@ choose_dsm_implementation(void)
 		char		name[64];
 		int			fd;
 
-		handle = random();
+		handle = pg_prng_uint32(&prng_state);
 		snprintf(name, 64, "/PostgreSQL.%u", handle);
 		if ((fd = shm_open(name, O_CREAT | O_RDWR | O_EXCL, 0600)) != -1)
 		{

src/bin/pg_test_fsync/pg_test_fsync.c

@@ -15,6 +15,7 @@
 
 #include "access/xlogdefs.h"
 #include "common/logging.h"
+#include "common/pg_prng.h"
 #include "getopt_long.h"
 
 /*
@@ -117,6 +118,8 @@ main(int argc, char *argv[])
 	pqsignal(SIGHUP, signal_cleanup);
 #endif
 
+	pg_prng_seed(&pg_global_prng_state, (uint64) time(NULL));
+
 	prepare_buf();
 
 	test_open();
@@ -233,7 +236,7 @@ prepare_buf(void)
 
 	/* write random data into buffer */
 	for (ops = 0; ops < DEFAULT_XLOG_SEG_SIZE; ops++)
-		full_buf[ops] = random();
+		full_buf[ops] = (char) pg_prng_int32(&pg_global_prng_state);
 
 	buf = (char *) TYPEALIGN(XLOG_BLCKSZ, full_buf);
 }

src/bin/pgbench/pgbench.c

@@ -59,6 +59,7 @@
 
 #include "common/int.h"
 #include "common/logging.h"
+#include "common/pg_prng.h"
 #include "common/string.h"
 #include "common/username.h"
 #include "fe_utils/cancel.h"
@@ -350,16 +351,8 @@ typedef struct StatsData
  */
 pg_time_usec_t epoch_shift;
 
-/*
- * Struct to keep random state.
- */
-typedef struct RandomState
-{
-	unsigned short xseed[3];
-} RandomState;
-
 /* Various random sequences are initialized from this one. */
-static RandomState base_random_sequence;
+static pg_prng_state base_random_sequence;
 
 /* Synchronization barrier for start and connection */
 static THREAD_BARRIER_T barrier;
@@ -461,7 +454,7 @@ typedef struct
 	 * Separate randomness for each client. This is used for random functions
 	 * PGBENCH_RANDOM_* during the execution of the script.
 	 */
-	RandomState cs_func_rs;
+	pg_prng_state cs_func_rs;
 
 	int			use_file;		/* index in sql_script for this client */
 	int			command;		/* command number in script */
@@ -498,9 +491,9 @@ typedef struct
 	 * random state to make all of them independent of each other and
 	 * therefore deterministic at the thread level.
 	 */
-	RandomState ts_choose_rs;	/* random state for selecting a script */
+	pg_prng_state ts_choose_rs; /* random state for selecting a script */
-	RandomState ts_throttle_rs; /* random state for transaction throttling */
+	pg_prng_state ts_throttle_rs;	/* random state for transaction throttling */
-	RandomState ts_sample_rs;	/* random state for log sampling */
+	pg_prng_state ts_sample_rs; /* random state for log sampling */
 
 	int64		throttle_trigger;	/* previous/next throttling (us) */
 	FILE	   *logfile;		/* where to log, or NULL */
@@ -898,42 +891,28 @@ strtodouble(const char *str, bool errorOK, double *dv)
 }
 
 /*
- * Initialize a random state struct.
+ * Initialize a prng state struct.
  *
  * We derive the seed from base_random_sequence, which must be set up already.
  */
 static void
-initRandomState(RandomState *random_state)
+initRandomState(pg_prng_state *state)
 {
-	random_state->xseed[0] = (unsigned short)
+	pg_prng_seed(state, pg_prng_uint64(&base_random_sequence));
-		(pg_jrand48(base_random_sequence.xseed) & 0xFFFF);
-	random_state->xseed[1] = (unsigned short)
-		(pg_jrand48(base_random_sequence.xseed) & 0xFFFF);
-	random_state->xseed[2] = (unsigned short)
-		(pg_jrand48(base_random_sequence.xseed) & 0xFFFF);
 }
 
+
 /*
- * Random number generator: uniform distribution from min to max inclusive.
+ * random number generator: uniform distribution from min to max inclusive.
  *
  * Although the limits are expressed as int64, you can't generate the full
  * int64 range in one call, because the difference of the limits mustn't
- * overflow int64.  In practice it's unwise to ask for more than an int32
+ * overflow int64.  This is not checked.
- * range, because of the limited precision of pg_erand48().
  */
 static int64
-getrand(RandomState *random_state, int64 min, int64 max)
+getrand(pg_prng_state *state, int64 min, int64 max)
 {
-	/*
+	return min + (int64) pg_prng_uint64_range(state, 0, max - min);
-	 * Odd coding is so that min and max have approximately the same chance of
-	 * being selected as do numbers between them.
-	 *
-	 * pg_erand48() is thread-safe and concurrent, which is why we use it
-	 * rather than random(), which in glibc is non-reentrant, and therefore
-	 * protected by a mutex, and therefore a bottleneck on machines with many
-	 * CPUs.
-	 */
-	return min + (int64) ((max - min + 1) * pg_erand48(random_state->xseed));
 }
 
 /*
@@ -942,7 +921,7 @@ getrand(RandomState *random_state, int64 min, int64 max)
  * value is exp(-parameter).
  */
 static int64
-getExponentialRand(RandomState *random_state, int64 min, int64 max,
+getExponentialRand(pg_prng_state *state, int64 min, int64 max,
 				   double parameter)
 {
 	double		cut,
@@ -952,8 +931,8 @@ getExponentialRand(RandomState *random_state, int64 min, int64 max,
 	/* abort if wrong parameter, but must really be checked beforehand */
 	Assert(parameter > 0.0);
 	cut = exp(-parameter);
-	/* erand in [0, 1), uniform in (0, 1] */
+	/* pg_prng_double value in [0, 1), uniform in (0, 1] */
-	uniform = 1.0 - pg_erand48(random_state->xseed);
+	uniform = 1.0 - pg_prng_double(state);
 
 	/*
 	 * inner expression in (cut, 1] (if parameter > 0), rand in [0, 1)
@@ -966,7 +945,7 @@ getExponentialRand(RandomState *random_state, int64 min, int64 max,
 
 /* random number generator: gaussian distribution from min to max inclusive */
 static int64
-getGaussianRand(RandomState *random_state, int64 min, int64 max,
+getGaussianRand(pg_prng_state *state, int64 min, int64 max,
 				double parameter)
 {
 	double		stdev;
@@ -990,13 +969,13 @@ getGaussianRand(RandomState *random_state, int64 min, int64 max,
 	do
 	{
 		/*
-		 * pg_erand48 generates [0,1), but for the basic version of the
+		 * pg_prng_double generates [0, 1), but for the basic version of the
 		 * Box-Muller transform the two uniformly distributed random numbers
-		 * are expected in (0, 1] (see
+		 * are expected to be in (0, 1] (see
 		 * https://en.wikipedia.org/wiki/Box-Muller_transform)
 		 */
-		double		rand1 = 1.0 - pg_erand48(random_state->xseed);
+		double		rand1 = 1.0 - pg_prng_double(state);
-		double		rand2 = 1.0 - pg_erand48(random_state->xseed);
+		double		rand2 = 1.0 - pg_prng_double(state);
 
 		/* Box-Muller basic form transform */
 		double		var_sqrt = sqrt(-2.0 * log(rand1));
@@ -1026,7 +1005,7 @@ getGaussianRand(RandomState *random_state, int64 min, int64 max,
  * not be one.
  */
 static int64
-getPoissonRand(RandomState *random_state, double center)
+getPoissonRand(pg_prng_state *state, double center)
 {
 	/*
 	 * Use inverse transform sampling to generate a value > 0, such that the
@@ -1034,8 +1013,8 @@ getPoissonRand(RandomState *random_state, double center)
 	 */
 	double		uniform;
 
-	/* erand in [0, 1), uniform in (0, 1] */
+	/* pg_prng_double value in [0, 1), uniform in (0, 1] */
-	uniform = 1.0 - pg_erand48(random_state->xseed);
+	uniform = 1.0 - pg_prng_double(state);
 
 	return (int64) (-log(uniform) * center + 0.5);
 }
@@ -1048,7 +1027,7 @@ getPoissonRand(RandomState *random_state, double center)
  * This works for s > 1.0, but may perform badly for s very close to 1.0.
  */
 static int64
-computeIterativeZipfian(RandomState *random_state, int64 n, double s)
+computeIterativeZipfian(pg_prng_state *state, int64 n, double s)
 {
 	double		b = pow(2.0, s - 1.0);
 	double		x,
@@ -1063,8 +1042,8 @@ computeIterativeZipfian(RandomState *random_state, int64 n, double s)
 	while (true)
 	{
 		/* random variates */
-		u = pg_erand48(random_state->xseed);
+		u = pg_prng_double(state);
-		v = pg_erand48(random_state->xseed);
+		v = pg_prng_double(state);
 
 		x = floor(pow(u, -1.0 / (s - 1.0)));
 
@@ -1078,14 +1057,14 @@ computeIterativeZipfian(RandomState *random_state, int64 n, double s)
 
 /* random number generator: zipfian distribution from min to max inclusive */
 static int64
-getZipfianRand(RandomState *random_state, int64 min, int64 max, double s)
+getZipfianRand(pg_prng_state *state, int64 min, int64 max, double s)
 {
 	int64		n = max - min + 1;
 
 	/* abort if parameter is invalid */
 	Assert(MIN_ZIPFIAN_PARAM <= s && s <= MAX_ZIPFIAN_PARAM);
 
-	return min - 1 + computeIterativeZipfian(random_state, n, s);
+	return min - 1 + computeIterativeZipfian(state, n, s);
 }
 
 /*
@@ -1142,7 +1121,7 @@ getHashMurmur2(int64 val, uint64 seed)
  * For small sizes, this generates each of the (size!) possible permutations
  * of integers in the range [0, size) with roughly equal probability.  Once
  * the size is larger than 20, the number of possible permutations exceeds the
- * number of distinct states of the internal pseudorandom number generators,
+ * number of distinct states of the internal pseudorandom number generator,
  * and so not all possible permutations can be generated, but the permutations
  * chosen should continue to give the appearance of being random.
  *
@@ -1152,8 +1131,8 @@ getHashMurmur2(int64 val, uint64 seed)
 static int64
 permute(const int64 val, const int64 isize, const int64 seed)
 {
-	RandomState random_state1;
+	/* using a high-end PRNG is probably overkill */
-	RandomState random_state2;
+	pg_prng_state state;
 	uint64		size;
 	uint64		v;
 	int			masklen;
@@ -1163,14 +1142,8 @@ permute(const int64 val, const int64 isize, const int64 seed)
 	if (isize < 2)
 		return 0;				/* nothing to permute */
 
-	/* Initialize a pair of random states using the seed */
+	/* Initialize prng state using the seed */
-	random_state1.xseed[0] = seed & 0xFFFF;
+	pg_prng_seed(&state, (uint64) seed);
-	random_state1.xseed[1] = (seed >> 16) & 0xFFFF;
-	random_state1.xseed[2] = (seed >> 32) & 0xFFFF;
-
-	random_state2.xseed[0] = (((uint64) seed) >> 48) & 0xFFFF;
-	random_state2.xseed[1] = seed & 0xFFFF;
-	random_state2.xseed[2] = (seed >> 16) & 0xFFFF;
 
 	/* Computations are performed on unsigned values */
 	size = (uint64) isize;
@@ -1216,8 +1189,8 @@ permute(const int64 val, const int64 isize, const int64 seed)
 					t;
 
 		/* Random multiply (by an odd number), XOR and rotate of lower half */
-		m = (uint64) getrand(&random_state1, 0, mask) | 1;
+		m = (pg_prng_uint64(&state) & mask) | 1;
-		r = (uint64) getrand(&random_state2, 0, mask);
+		r = pg_prng_uint64(&state) & mask;
 		if (v <= mask)
 		{
 			v = ((v * m) ^ r) & mask;
@@ -1225,8 +1198,8 @@ permute(const int64 val, const int64 isize, const int64 seed)
 		}
 
 		/* Random multiply (by an odd number), XOR and rotate of upper half */
-		m = (uint64) getrand(&random_state1, 0, mask) | 1;
+		m = (pg_prng_uint64(&state) & mask) | 1;
-		r = (uint64) getrand(&random_state2, 0, mask);
+		r = pg_prng_uint64(&state) & mask;
 		t = size - 1 - v;
 		if (t <= mask)
 		{
@@ -1236,7 +1209,7 @@ permute(const int64 val, const int64 isize, const int64 seed)
 		}
 
 		/* Random offset */
-		r = (uint64) getrand(&random_state2, 0, size - 1);
+		r = pg_prng_uint64_range(&state, 0, size - 1);
 		v = (v + r) % size;
 	}
 
@@ -3831,7 +3804,7 @@ doLog(TState *thread, CState *st,
 	 * to the random sample.
 	 */
 	if (sample_rate != 0.0 &&
-		pg_erand48(thread->ts_sample_rs.xseed) > sample_rate)
+		pg_prng_double(&thread->ts_sample_rs) > sample_rate)
 		return;
 
 	/* should we aggregate the results or not? */
@@ -5770,12 +5743,11 @@ set_random_seed(const char *seed)
 
 	if (seed != NULL)
 		pg_log_info("setting random seed to %llu", (unsigned long long) iseed);
+
 	random_seed = iseed;
 
-	/* Fill base_random_sequence with low-order bits of seed */
+	/* Initialize base_random_sequence using seed */
-	base_random_sequence.xseed[0] = iseed & 0xFFFF;
+	pg_prng_seed(&base_random_sequence, (uint64) iseed);
-	base_random_sequence.xseed[1] = (iseed >> 16) & 0xFFFF;
-	base_random_sequence.xseed[2] = (iseed >> 32) & 0xFFFF;
 
 	return true;
 }
@@ -6449,9 +6421,7 @@ main(int argc, char **argv)
 	/* set default seed for hash functions */
 	if (lookupVariable(&state[0], "default_seed") == NULL)
 	{
-		uint64		seed =
+		uint64		seed = pg_prng_uint64(&base_random_sequence);
-		((uint64) pg_jrand48(base_random_sequence.xseed) & 0xFFFFFFFF) |
-		(((uint64) pg_jrand48(base_random_sequence.xseed) & 0xFFFFFFFF) << 32);
 
 		for (i = 0; i < nclients; i++)
 			if (!putVariableInt(&state[i], "startup", "default_seed", (int64) seed))

src/bin/pgbench/t/001_pgbench_with_server.pl

@@ -369,7 +369,6 @@ $node->append_conf('postgresql.conf',
 $node->reload;
 
 # test expressions
-# command 1..3 and 23 depend on random seed which is used to call srandom.
 $node->pgbench(
 	'--random-seed=5432 -t 1 -Dfoo=-10.1 -Dbla=false -Di=+3 -Dn=null -Dt=t -Df=of -Dd=1.0',
 	0,
@@ -378,9 +377,9 @@ $node->pgbench(
 		qr{setting random seed to 5432\b},
 
 		# After explicit seeding, the four random checks (1-3,20) are
-		# deterministic
+		# deterministic; but see also magic values in checks 111,113.
-		qr{command=1.: int 13\b},      # uniform random
+		qr{command=1.: int 17\b},      # uniform random
-		qr{command=2.: int 116\b},     # exponential random
+		qr{command=2.: int 104\b},     # exponential random
 		qr{command=3.: int 1498\b},    # gaussian random
 		qr{command=4.: int 4\b},
 		qr{command=5.: int 5\b},
@@ -394,7 +393,7 @@ $node->pgbench(
 		qr{command=15.: double 15\b},
 		qr{command=16.: double 16\b},
 		qr{command=17.: double 17\b},
-		qr{command=20.: int 1\b},    # zipfian random
+		qr{command=20.: int 3\b},    # zipfian random
 		qr{command=21.: double -27\b},
 		qr{command=22.: double 1024\b},
 		qr{command=23.: double 1\b},
@@ -448,6 +447,7 @@ $node->pgbench(
 		qr{command=109.: boolean true\b},
 		qr{command=110.: boolean true\b},
 		qr{command=111.: boolean true\b},
+		qr{command=113.: boolean true\b},
 	],
 	'pgbench expressions',
 	{
@@ -591,8 +591,17 @@ SELECT :v0, :v1, :v2, :v3;
 \set t debug(0 <= :p and :p < :size and :p = permute(:v + :size, :size) and :p <> permute(:v + 1, :size))
 -- actual values
 \set t debug(permute(:v, 1) = 0)
-\set t debug(permute(0, 2, 5432) = 0 and permute(1, 2, 5432) = 1 and \
+\set t debug(permute(0, 2, 5431) = 0 and permute(1, 2, 5431) = 1 and \
-             permute(0, 2, 5435) = 1 and permute(1, 2, 5435) = 0)
+             permute(0, 2, 5433) = 1 and permute(1, 2, 5433) = 0)
+-- check permute's portability across architectures
+\set size debug(:max - 10)
+\set t debug(permute(:size-1, :size, 5432) = 520382784483822430 and \
+             permute(:size-2, :size, 5432) = 1143715004660802862 and \
+             permute(:size-3, :size, 5432) = 447293596416496998 and \
+             permute(:size-4, :size, 5432) = 916527772266572956 and \
+             permute(:size-5, :size, 5432) = 2763809008686028849 and \
+             permute(:size-6, :size, 5432) = 8648551549198294572 and \
+             permute(:size-7, :size, 5432) = 4542876852200565125)
 }
 	});
 

src/common/Makefile

@@ -66,6 +66,7 @@ OBJS_COMMON = \
 	md5_common.o \
 	pg_get_line.o \
 	pg_lzcompress.o \
+	pg_prng.o \
 	pgfnames.o \
 	psprintf.o \
 	relpath.o \

src/common/pg_prng.c

@@ -0,0 +1,247 @@
+/*-------------------------------------------------------------------------
+ *
+ * Pseudo-Random Number Generator
+ *
+ * We use Blackman and Vigna's xoroshiro128** 1.0 algorithm
+ * to have a small, fast PRNG suitable for generating reasonably
+ * good-quality 64-bit data.  This should not be considered
+ * cryptographically strong, however.
+ *
+ * About these generators: https://prng.di.unimi.it/
+ * See also https://en.wikipedia.org/wiki/List_of_random_number_generators
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ *
+ * src/common/pg_prng.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+#include <math.h>				/* for ldexp() */
+
+#include "common/pg_prng.h"
+#include "port/pg_bitutils.h"
+
+/* process-wide state vector */
+pg_prng_state pg_global_prng_state;
+
+
+/*
+ * 64-bit rotate left
+ */
+static inline uint64
+rotl(uint64 x, int bits)
+{
+	return (x << bits) | (x >> (64 - bits));
+}
+
+/*
+ * The basic xoroshiro128** algorithm.
+ * Generates and returns a 64-bit uniformly distributed number,
+ * updating the state vector for next time.
+ *
+ * Note: the state vector must not be all-zeroes, as that is a fixed point.
+ */
+static uint64
+xoroshiro128ss(pg_prng_state *state)
+{
+	uint64		s0 = state->s0,
+				sx = state->s1 ^ s0,
+				val = rotl(s0 * 5, 7) * 9;
+
+	/* update state */
+	state->s0 = rotl(s0, 24) ^ sx ^ (sx << 16);
+	state->s1 = rotl(sx, 37);
+
+	return val;
+}
+
+/*
+ * We use this generator just to fill the xoroshiro128** state vector
+ * from a 64-bit seed.
+ */
+static uint64
+splitmix64(uint64 *state)
+{
+	/* state update */
+	uint64		val = (*state += UINT64CONST(0x9E3779B97f4A7C15));
+
+	/* value extraction */
+	val = (val ^ (val >> 30)) * UINT64CONST(0xBF58476D1CE4E5B9);
+	val = (val ^ (val >> 27)) * UINT64CONST(0x94D049BB133111EB);
+
+	return val ^ (val >> 31);
+}
+
+/*
+ * Initialize the PRNG state from a 64-bit integer,
+ * taking care that we don't produce all-zeroes.
+ */
+void
+pg_prng_seed(pg_prng_state *state, uint64 seed)
+{
+	state->s0 = splitmix64(&seed);
+	state->s1 = splitmix64(&seed);
+	/* Let's just make sure we didn't get all-zeroes */
+	(void) pg_prng_seed_check(state);
+}
+
+/*
+ * Initialize the PRNG state from a double in the range [-1.0, 1.0],
+ * taking care that we don't produce all-zeroes.
+ */
+void
+pg_prng_fseed(pg_prng_state *state, double fseed)
+{
+	/* Assume there's about 52 mantissa bits; the sign contributes too. */
+	int64		seed = ((double) ((UINT64CONST(1) << 52) - 1)) * fseed;
+
+	pg_prng_seed(state, (uint64) seed);
+}
+
+/*
+ * Validate a PRNG seed value.
+ */
+bool
+pg_prng_seed_check(pg_prng_state *state)
+{
+	/*
+	 * If the seeding mechanism chanced to produce all-zeroes, insert
+	 * something nonzero.  Anything would do; use Knuth's LCG parameters.
+	 */
+	if (unlikely(state->s0 == 0 && state->s1 == 0))
+	{
+		state->s0 = UINT64CONST(0x5851F42D4C957F2D);
+		state->s1 = UINT64CONST(0x14057B7EF767814F);
+	}
+
+	/* As a convenience for the pg_prng_strong_seed macro, return true */
+	return true;
+}
+
+/*
+ * Select a random uint64 uniformly from the range [0, PG_UINT64_MAX].
+ */
+uint64
+pg_prng_uint64(pg_prng_state *state)
+{
+	return xoroshiro128ss(state);
+}
+
+/*
+ * Select a random uint64 uniformly from the range [rmin, rmax].
+ * If the range is empty, rmin is always produced.
+ */
+uint64
+pg_prng_uint64_range(pg_prng_state *state, uint64 rmin, uint64 rmax)
+{
+	uint64		val;
+
+	if (likely(rmax > rmin))
+	{
+		/*
+		 * Use bitmask rejection method to generate an offset in 0..range.
+		 * Each generated val is less than twice "range", so on average we
+		 * should not have to iterate more than twice.
+		 */
+		uint64		range = rmax - rmin;
+		uint32		rshift = 63 - pg_leftmost_one_pos64(range);
+
+		do
+		{
+			val = xoroshiro128ss(state) >> rshift;
+		} while (val > range);
+	}
+	else
+		val = 0;
+
+	return rmin + val;
+}
+
+/*
+ * Select a random int64 uniformly from the range [PG_INT64_MIN, PG_INT64_MAX].
+ */
+int64
+pg_prng_int64(pg_prng_state *state)
+{
+	return (int64) xoroshiro128ss(state);
+}
+
+/*
+ * Select a random int64 uniformly from the range [0, PG_INT64_MAX].
+ */
+int64
+pg_prng_int64p(pg_prng_state *state)
+{
+	return (int64) (xoroshiro128ss(state) & UINT64CONST(0x7FFFFFFFFFFFFFFF));
+}
+
+/*
+ * Select a random uint32 uniformly from the range [0, PG_UINT32_MAX].
+ */
+uint32
+pg_prng_uint32(pg_prng_state *state)
+{
+	/*
+	 * Although xoroshiro128** is not known to have any weaknesses in
+	 * randomness of low-order bits, we prefer to use the upper bits of its
+	 * result here and below.
+	 */
+	uint64		v = xoroshiro128ss(state);
+
+	return (uint32) (v >> 32);
+}
+
+/*
+ * Select a random int32 uniformly from the range [PG_INT32_MIN, PG_INT32_MAX].
+ */
+int32
+pg_prng_int32(pg_prng_state *state)
+{
+	uint64		v = xoroshiro128ss(state);
+
+	return (int32) (v >> 32);
+}
+
+/*
+ * Select a random int32 uniformly from the range [0, PG_INT32_MAX].
+ */
+int32
+pg_prng_int32p(pg_prng_state *state)
+{
+	uint64		v = xoroshiro128ss(state);
+
+	return (int32) (v >> 33);
+}
+
+/*
+ * Select a random double uniformly from the range [0.0, 1.0).
+ *
+ * Note: if you want a result in the range (0.0, 1.0], the standard way
+ * to get that is "1.0 - pg_prng_double(state)".
+ */
+double
+pg_prng_double(pg_prng_state *state)
+{
+	uint64		v = xoroshiro128ss(state);
+
+	/*
+	 * As above, assume there's 52 mantissa bits in a double.  This result
+	 * could round to 1.0 if double's precision is less than that; but we
+	 * assume IEEE float arithmetic elsewhere in Postgres, so this seems OK.
+	 */
+	return ldexp((double) (v >> (64 - 52)), -52);
+}
+
+/*
+ * Select a random boolean value.
+ */
+bool
+pg_prng_bool(pg_prng_state *state)
+{
+	uint64		v = xoroshiro128ss(state);
+
+	return (bool) (v >> 63);
+}

src/include/common/pg_prng.h

@@ -0,0 +1,60 @@
+/*-------------------------------------------------------------------------
+ *
+ * Pseudo-Random Number Generator
+ *
+ * Copyright (c) 2021, PostgreSQL Global Development Group
+ *
+ * src/include/common/pg_prng.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_PRNG_H
+#define PG_PRNG_H
+
+/*
+ * State vector for PRNG generation.  Callers should treat this as an
+ * opaque typedef, but we expose its definition to allow it to be
+ * embedded in other structs.
+ */
+typedef struct pg_prng_state
+{
+	uint64		s0,
+				s1;
+} pg_prng_state;
+
+/*
+ * Callers not needing local PRNG series may use this global state vector,
+ * after initializing it with one of the pg_prng_...seed functions.
+ */
+extern PGDLLIMPORT pg_prng_state pg_global_prng_state;
+
+extern void pg_prng_seed(pg_prng_state *state, uint64 seed);
+extern void pg_prng_fseed(pg_prng_state *state, double fseed);
+extern bool pg_prng_seed_check(pg_prng_state *state);
+
+/*
+ * Initialize the PRNG state from the pg_strong_random source,
+ * taking care that we don't produce all-zeroes.  If this returns false,
+ * caller should initialize the PRNG state from some other random seed,
+ * using pg_prng_[f]seed.
+ *
+ * We implement this as a macro, so that the pg_strong_random() call is
+ * in the caller.  If it were in pg_prng.c, programs using pg_prng.c
+ * but not needing strong seeding would nonetheless be forced to pull in
+ * pg_strong_random.c and thence OpenSSL.
+ */
+#define pg_prng_strong_seed(state) \
+	(pg_strong_random((void *) (state), sizeof(pg_prng_state)) ? \
+	 pg_prng_seed_check(state) : false)
+
+extern uint64 pg_prng_uint64(pg_prng_state *state);
+extern uint64 pg_prng_uint64_range(pg_prng_state *state, uint64 rmin, uint64 rmax);
+extern int64 pg_prng_int64(pg_prng_state *state);
+extern int64 pg_prng_int64p(pg_prng_state *state);
+extern uint32 pg_prng_uint32(pg_prng_state *state);
+extern int32 pg_prng_int32(pg_prng_state *state);
+extern int32 pg_prng_int32p(pg_prng_state *state);
+extern double pg_prng_double(pg_prng_state *state);
+extern bool pg_prng_bool(pg_prng_state *state);
+
+#endif							/* PG_PRNG_H */

src/include/optimizer/geqo.h

@@ -22,6 +22,7 @@
 #ifndef GEQO_H
 #define GEQO_H
 
+#include "common/pg_prng.h"
 #include "nodes/pathnodes.h"
 #include "optimizer/geqo_gene.h"
 
@@ -73,7 +74,7 @@ extern double Geqo_seed;		/* 0 .. 1 */
 typedef struct
 {
 	List	   *initial_rels;	/* the base relations we are joining */
-	unsigned short random_state[3]; /* state for pg_erand48() */
+	pg_prng_state random_state; /* PRNG state */
 } GeqoPrivateData;
 
 

src/include/optimizer/geqo_random.h

@@ -31,11 +31,10 @@
 
 extern void geqo_set_seed(PlannerInfo *root, double seed);
 
-/* geqo_rand returns a random float value between 0 and 1 inclusive */
+/* geqo_rand returns a random float value in the range [0.0, 1.0) */
 extern double geqo_rand(PlannerInfo *root);
 
 /* geqo_randint returns integer value between lower and upper inclusive */
-#define geqo_randint(root, upper, lower) \
+extern int	geqo_randint(PlannerInfo *root, int upper, int lower);
-	( (int) floor( geqo_rand(root)*(((upper)-(lower))+0.999999) ) + (lower) )
 
 #endif							/* GEQO_RANDOM_H */

src/include/pg_config.h.in

@@ -445,9 +445,6 @@
 /* Define to 1 if you have the `pwrite' function. */
 #undef HAVE_PWRITE
 
-/* Define to 1 if you have the `random' function. */
-#undef HAVE_RANDOM
-
 /* Define to 1 if you have the <readline.h> header file. */
 #undef HAVE_READLINE_H
 
@@ -512,9 +509,6 @@
 /* Define to 1 if you have spinlocks. */
 #undef HAVE_SPINLOCKS
 
-/* Define to 1 if you have the `srandom' function. */
-#undef HAVE_SRANDOM
-
 /* Define to 1 if stdbool.h conforms to C99. */
 #undef HAVE_STDBOOL_H
 

src/include/pg_config_manual.h

@@ -234,17 +234,6 @@
  */
 #define DEFAULT_EVENT_SOURCE  "PostgreSQL"
 
-/*
- * The random() function is expected to yield values between 0 and
- * MAX_RANDOM_VALUE.  Currently, all known implementations yield
- * 0..2^31-1, so we just hardwire this constant.  We could do a
- * configure test if it proves to be necessary.  CAUTION: Think not to
- * replace this with RAND_MAX.  RAND_MAX defines the maximum value of
- * the older rand() function, which is often different from --- and
- * considerably inferior to --- random().
- */
-#define MAX_RANDOM_VALUE  PG_INT32_MAX
-
 /*
  * On PPC machines, decide whether to use the mutex hint bit in LWARX
  * instructions.  Setting the hint bit will slightly improve spinlock

src/include/port.h

@@ -362,11 +362,6 @@ extern int	gettimeofday(struct timeval *tp, struct timezone *tzp);
 #define pgoff_t off_t
 #endif
 
-extern double pg_erand48(unsigned short xseed[3]);
-extern long pg_lrand48(void);
-extern long pg_jrand48(unsigned short xseed[3]);
-extern void pg_srand48(long seed);
-
 #ifndef HAVE_FLS
 extern int	fls(int mask);
 #endif
@@ -452,10 +447,6 @@ extern size_t strlcpy(char *dst, const char *src, size_t siz);
 extern size_t strnlen(const char *str, size_t maxlen);
 #endif
 
-#if !defined(HAVE_RANDOM)
-extern long random(void);
-#endif
-
 #ifndef HAVE_SETENV
 extern int	setenv(const char *name, const char *value, int overwrite);
 #endif
@@ -464,10 +455,6 @@ extern int	setenv(const char *name, const char *value, int overwrite);
 extern int	unsetenv(const char *name);
 #endif
 
-#ifndef HAVE_SRANDOM
-extern void srandom(unsigned int seed);
-#endif
-
 #ifndef HAVE_DLOPEN
 extern void *dlopen(const char *file, int mode);
 extern void *dlsym(void *handle, const char *symbol);

src/include/utils/sampling.h

@@ -13,15 +13,14 @@
 #ifndef SAMPLING_H
 #define SAMPLING_H
 
+#include "common/pg_prng.h"
 #include "storage/block.h"		/* for typedef BlockNumber */
 
 
 /* Random generator for sampling code */
-typedef unsigned short SamplerRandomState[3];
+extern void sampler_random_init_state(uint32 seed,
-
+									  pg_prng_state *randstate);
-extern void sampler_random_init_state(long seed,
+extern double sampler_random_fract(pg_prng_state *randstate);
-									  SamplerRandomState randstate);
-extern double sampler_random_fract(SamplerRandomState randstate);
 
 /* Block sampling methods */
 
@@ -32,13 +31,13 @@ typedef struct
 	int			n;				/* desired sample size */
 	BlockNumber t;				/* current block number */
 	int			m;				/* blocks selected so far */
-	SamplerRandomState randstate;	/* random generator state */
+	pg_prng_state randstate;	/* random generator state */
 } BlockSamplerData;
 
 typedef BlockSamplerData *BlockSampler;
 
 extern BlockNumber BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
-									 int samplesize, long randseed);
+									 int samplesize, uint32 randseed);
 extern bool BlockSampler_HasMore(BlockSampler bs);
 extern BlockNumber BlockSampler_Next(BlockSampler bs);
 
@@ -47,7 +46,7 @@ extern BlockNumber BlockSampler_Next(BlockSampler bs);
 typedef struct
 {
 	double		W;
-	SamplerRandomState randstate;	/* random generator state */
+	pg_prng_state randstate;	/* random generator state */
 } ReservoirStateData;
 
 typedef ReservoirStateData *ReservoirState;

src/port/Makefile

@@ -42,7 +42,6 @@ OBJS = \
 	$(PG_CRC32C_OBJS) \
 	bsearch_arg.o \
 	chklocale.o \
-	erand48.o \
 	inet_net_ntop.o \
 	noblock.o \
 	path.o \

src/port/erand48.c

@@ -1,136 +0,0 @@
-/*-------------------------------------------------------------------------
- *
- * erand48.c
- *
- * This file supplies pg_erand48() and related functions, which except
- * for the names are just like the POSIX-standard erand48() family.
- * (We don't supply the full set though, only the ones we have found use
- * for in Postgres.  In particular, we do *not* implement lcong48(), so
- * that there is no need for the multiplier and addend to be variable.)
- *
- * We used to test for an operating system version rather than
- * unconditionally using our own, but (1) some versions of Cygwin have a
- * buggy erand48() that always returns zero and (2) as of 2011, glibc's
- * erand48() is strangely coded to be almost-but-not-quite thread-safe,
- * which doesn't matter for the backend but is important for pgbench.
- *
- * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
- *
- * Portions Copyright (c) 1993 Martin Birgmeier
- * All rights reserved.
- *
- * You may redistribute unmodified or modified versions of this source
- * code provided that the above copyright notice and this and the
- * following conditions are retained.
- *
- * This software is provided ``as is'', and comes with no warranties
- * of any kind. I shall in no event be liable for anything that happens
- * to anyone/anything when using this software.
- *
- * IDENTIFICATION
- *	  src/port/erand48.c
- *
- *-------------------------------------------------------------------------
- */
-
-#include "c.h"
-
-#include <math.h>
-
-/* These values are specified by POSIX */
-#define RAND48_MULT		UINT64CONST(0x0005deece66d)
-#define RAND48_ADD		UINT64CONST(0x000b)
-
-/* POSIX specifies 0x330e's use in srand48, but the other bits are arbitrary */
-#define RAND48_SEED_0	(0x330e)
-#define RAND48_SEED_1	(0xabcd)
-#define RAND48_SEED_2	(0x1234)
-
-static unsigned short _rand48_seed[3] = {
-	RAND48_SEED_0,
-	RAND48_SEED_1,
-	RAND48_SEED_2
-};
-
-
-/*
- * Advance the 48-bit value stored in xseed[] to the next "random" number.
- *
- * Also returns the value of that number --- without masking it to 48 bits.
- * If caller uses the result, it must mask off the bits it wants.
- */
-static uint64
-_dorand48(unsigned short xseed[3])
-{
-	/*
-	 * We do the arithmetic in uint64; any type wider than 48 bits would work.
-	 */
-	uint64		in;
-	uint64		out;
-
-	in = (uint64) xseed[2] << 32 | (uint64) xseed[1] << 16 | (uint64) xseed[0];
-
-	out = in * RAND48_MULT + RAND48_ADD;
-
-	xseed[0] = out & 0xFFFF;
-	xseed[1] = (out >> 16) & 0xFFFF;
-	xseed[2] = (out >> 32) & 0xFFFF;
-
-	return out;
-}
-
-
-/*
- * Generate a random floating-point value using caller-supplied state.
- * Values are uniformly distributed over the interval [0.0, 1.0).
- */
-double
-pg_erand48(unsigned short xseed[3])
-{
-	uint64		x = _dorand48(xseed);
-
-	return ldexp((double) (x & UINT64CONST(0xFFFFFFFFFFFF)), -48);
-}
-
-/*
- * Generate a random non-negative integral value using internal state.
- * Values are uniformly distributed over the interval [0, 2^31).
- */
-long
-pg_lrand48(void)
-{
-	uint64		x = _dorand48(_rand48_seed);
-
-	return (x >> 17) & UINT64CONST(0x7FFFFFFF);
-}
-
-/*
- * Generate a random signed integral value using caller-supplied state.
- * Values are uniformly distributed over the interval [-2^31, 2^31).
- */
-long
-pg_jrand48(unsigned short xseed[3])
-{
-	uint64		x = _dorand48(xseed);
-
-	return (int32) ((x >> 16) & UINT64CONST(0xFFFFFFFF));
-}
-
-/*
- * Initialize the internal state using the given seed.
- *
- * Per POSIX, this uses only 32 bits from "seed" even if "long" is wider.
- * Hence, the set of possible seed values is smaller than it could be.
- * Better practice is to use caller-supplied state and initialize it with
- * random bits obtained from a high-quality source of random bits.
- *
- * Note: POSIX specifies a function seed48() that allows all 48 bits
- * of the internal state to be set, but we don't currently support that.
- */
-void
-pg_srand48(long seed)
-{
-	_rand48_seed[0] = RAND48_SEED_0;
-	_rand48_seed[1] = (unsigned short) seed;
-	_rand48_seed[2] = (unsigned short) (seed >> 16);
-}

src/port/random.c

@@ -1,25 +0,0 @@
-/*-------------------------------------------------------------------------
- *
- * random.c
- *	  random() wrapper
- *
- * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
- * Portions Copyright (c) 1994, Regents of the University of California
- *
- *
- * IDENTIFICATION
- *	  src/port/random.c
- *
- *-------------------------------------------------------------------------
- */
-
-#include "c.h"
-
-#include <math.h>
-
-
-long
-random(void)
-{
-	return pg_lrand48();
-}

src/port/srandom.c

@@ -1,25 +0,0 @@
-/*-------------------------------------------------------------------------
- *
- * srandom.c
- *	  srandom() wrapper
- *
- * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
- * Portions Copyright (c) 1994, Regents of the University of California
- *
- *
- * IDENTIFICATION
- *	  src/port/srandom.c
- *
- *-------------------------------------------------------------------------
- */
-
-#include "c.h"
-
-#include <math.h>
-
-
-void
-srandom(unsigned int seed)
-{
-	pg_srand48((long int) seed);
-}

src/test/modules/test_bloomfilter/test_bloomfilter.c

@@ -12,6 +12,7 @@
  */
 #include "postgres.h"
 
+#include "common/pg_prng.h"
 #include "fmgr.h"
 #include "lib/bloomfilter.h"
 #include "miscadmin.h"
@@ -83,9 +84,8 @@ create_and_test_bloom(int power, int64 nelements, int callerseed)
 	 * Generate random seed, or use caller's.  Seed should always be a
 	 * positive value less than or equal to PG_INT32_MAX, to ensure that any
 	 * random seed can be recreated through callerseed if the need arises.
-	 * (Don't assume that RAND_MAX cannot exceed PG_INT32_MAX.)
 	 */
-	seed = callerseed < 0 ? random() % PG_INT32_MAX : callerseed;
+	seed = callerseed < 0 ? pg_prng_int32p(&pg_global_prng_state) : callerseed;
 
 	/* Create Bloom filter, populate it, and report on false positive rate */
 	filter = bloom_create(nelements, bloom_work_mem, seed);

src/test/modules/test_integerset/test_integerset.c

@@ -12,6 +12,7 @@
  */
 #include "postgres.h"
 
+#include "common/pg_prng.h"
 #include "fmgr.h"
 #include "lib/integerset.h"
 #include "miscadmin.h"
@@ -248,8 +249,7 @@ test_pattern(const test_spec *spec)
 		 * only a small part of the integer space is used.  We would very
 		 * rarely hit values that are actually in the set.
 		 */
-		x = (pg_lrand48() << 31) | pg_lrand48();
+		x = pg_prng_uint64_range(&pg_global_prng_state, 0, last_int + 1000);
-		x = x % (last_int + 1000);
 
 		/* Do we expect this value to be present in the set? */
 		if (x >= last_int)
@@ -571,7 +571,7 @@ test_huge_distances(void)
 	 */
 	while (num_values < 1000)
 	{
-		val += pg_lrand48();
+		val += pg_prng_uint32(&pg_global_prng_state);
 		values[num_values++] = val;
 	}
 

src/test/modules/test_rbtree/test_rbtree.c

@@ -13,6 +13,7 @@
 
 #include "postgres.h"
 
+#include "common/pg_prng.h"
 #include "fmgr.h"
 #include "lib/rbtree.h"
 #include "utils/memutils.h"
@@ -108,7 +109,7 @@ GetPermutation(int size)
 	 */
 	for (i = 1; i < size; i++)
 	{
-		int			j = random() % (i + 1);
+		int			j = pg_prng_uint64_range(&pg_global_prng_state, 0, i);
 
 		if (j < i)				/* avoid fetching undefined data if j=i */
 			permutation[i] = permutation[j];
@@ -320,7 +321,7 @@ testdelete(int size, int delsize)
 
 	for (i = 0; i < delsize; i++)
 	{
-		int			k = random() % size;
+		int			k = pg_prng_uint64_range(&pg_global_prng_state, 0, size - 1);
 
 		while (chosen[k])
 			k = (k + 1) % size;

src/tools/msvc/Mkvcbuild.pm

@@ -99,9 +99,9 @@ sub mkvcbuild
 	$solution = CreateSolution($vsVersion, $config);
 
 	our @pgportfiles = qw(
-	  chklocale.c explicit_bzero.c fls.c getpeereid.c getrusage.c inet_aton.c random.c
+	  chklocale.c explicit_bzero.c fls.c getpeereid.c getrusage.c inet_aton.c
-	  srandom.c getaddrinfo.c gettimeofday.c inet_net_ntop.c kill.c open.c
+	  getaddrinfo.c gettimeofday.c inet_net_ntop.c kill.c open.c
-	  erand48.c snprintf.c strlcat.c strlcpy.c dirmod.c noblock.c path.c
+	  snprintf.c strlcat.c strlcpy.c dirmod.c noblock.c path.c
 	  dirent.c dlopen.c getopt.c getopt_long.c link.c
 	  pread.c preadv.c pwrite.c pwritev.c pg_bitutils.c
 	  pg_strong_random.c pgcheckdir.c pgmkdirp.c pgsleep.c pgstrcasecmp.c
@@ -127,9 +127,9 @@ sub mkvcbuild
 	  config_info.c controldata_utils.c d2s.c encnames.c exec.c
 	  f2s.c file_perm.c file_utils.c hashfn.c ip.c jsonapi.c
 	  keywords.c kwlookup.c link-canary.c md5_common.c
-	  pg_get_line.c pg_lzcompress.c pgfnames.c psprintf.c relpath.c rmtree.c
+	  pg_get_line.c pg_lzcompress.c pg_prng.c pgfnames.c psprintf.c relpath.c
-	  saslprep.c scram-common.c string.c stringinfo.c unicode_norm.c username.c
+	  rmtree.c saslprep.c scram-common.c string.c stringinfo.c unicode_norm.c
-	  wait_error.c wchar.c);
+	  username.c wait_error.c wchar.c);
 
 	if ($solution->{options}->{openssl})
 	{

src/tools/msvc/Solution.pm

@@ -342,7 +342,6 @@ sub GenerateFiles
 		HAVE_PTHREAD_IS_THREADED_NP => undef,
 		HAVE_PTHREAD_PRIO_INHERIT   => undef,
 		HAVE_PWRITE                 => undef,
-		HAVE_RANDOM                 => undef,
 		HAVE_READLINE_H             => undef,
 		HAVE_READLINE_HISTORY_H     => undef,
 		HAVE_READLINE_READLINE_H    => undef,
@@ -363,7 +362,6 @@ sub GenerateFiles
 		HAVE_SHM_OPEN                            => undef,
 		HAVE_SOCKLEN_T                           => 1,
 		HAVE_SPINLOCKS                           => 1,
-		HAVE_SRANDOM                             => undef,
 		HAVE_STDBOOL_H                           => 1,
 		HAVE_STDINT_H                            => 1,
 		HAVE_STDLIB_H                            => 1,

src/tools/testint128.c

@@ -27,6 +27,7 @@
 #endif
 
 #include "common/int128.h"
+#include "common/pg_prng.h"
 
 /*
  * We assume the parts of this union are laid out compatibly.
@@ -61,27 +62,11 @@ my_int128_compare(int128 x, int128 y)
 	return 0;
 }
 
-/*
- * Get a random uint64 value.
- * We don't assume random() is good for more than 16 bits.
- */
-static uint64
-get_random_uint64(void)
-{
-	uint64		x;
-
-	x = (uint64) (random() & 0xFFFF) << 48;
-	x |= (uint64) (random() & 0xFFFF) << 32;
-	x |= (uint64) (random() & 0xFFFF) << 16;
-	x |= (uint64) (random() & 0xFFFF);
-	return x;
-}
-
 /*
  * Main program.
  *
  * Generates a lot of random numbers and tests the implementation for each.
- * The results should be reproducible, since we don't call srandom().
+ * The results should be reproducible, since we use a fixed PRNG seed.
  *
  * You can give a loop count if you don't like the default 1B iterations.
  */
@@ -90,6 +75,8 @@ main(int argc, char **argv)
 {
 	long		count;
 
+	pg_prng_seed(&pg_global_prng_state, 0);
+
 	if (argc >= 2)
 		count = strtol(argv[1], NULL, 0);
 	else
@@ -97,9 +84,9 @@ main(int argc, char **argv)
 
 	while (count-- > 0)
 	{
-		int64		x = get_random_uint64();
+		int64		x = pg_prng_uint64(&pg_global_prng_state);
-		int64		y = get_random_uint64();
+		int64		y = pg_prng_uint64(&pg_global_prng_state);
-		int64		z = get_random_uint64();
+		int64		z = pg_prng_uint64(&pg_global_prng_state);
 		test128		t1;
 		test128		t2;
 
@@ -151,7 +138,7 @@ main(int argc, char **argv)
 		t1.hl.hi = x;
 		t1.hl.lo = y;
 		t2.hl.hi = z;
-		t2.hl.lo = get_random_uint64();
+		t2.hl.lo = pg_prng_uint64(&pg_global_prng_state);
 
 		if (my_int128_compare(t1.i128, t2.i128) !=
 			int128_compare(t1.I128, t2.I128))