</listitem>
</varlistentry>
+ <varlistentry>
+ <term><option>--random-seed=</option><replaceable>SEED</replaceable></term>
+ <listitem>
+ <para>
+ Set random generator seed. Seeds the system random number generator,
+ which then produces a sequence of initial generator states, one for
+ each thread.
+ Values for <replaceable>SEED</replaceable> may be:
+ <literal>time</literal> (the default, the seed is based on the current time),
+ <literal>rand</literal> (use a strong random source, failing if none
+ is available), or an unsigned decimal integer value.
+ The random generator is invoked explicitly from a pgbench script
+ (<literal>random...</literal> functions) or implicitly (for instance option
+ <option>--rate</option> uses it to schedule transactions).
+ When explicitly set, the value used for seeding is shown on the terminal.
+ Any value allowed for <replaceable>SEED</replaceable> may also be
+ provided through the environment variable
+ <literal>PGBENCH_RANDOM_SEED</literal>.
+ To ensure that the provided seed impacts all possible uses, put this option
+ first or use the environment variable.
+ </para>
+ <para>
+ Setting the seed explicitly allows to reproduce a <command>pgbench</command>
+ run exactly, as far as random numbers are concerned.
+ As the random state is managed per thread, this means the exact same
+ <command>pgbench</command> run for an identical invocation if there is one
+ client per thread and there are no external or data dependencies.
+ From a statistical viewpoint reproducing runs exactly is a bad idea because
+ it can hide the performance variability or improve performance unduly,
+ e.g. by hitting the same pages as a previous run.
+ However, it may also be of great help for debugging, for instance
+ re-running a tricky case which leads to an error.
+ Use wisely.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term><option>--sampling-rate=<replaceable>rate</replaceable></option></term>
<listitem>
<entry>seed used in hash functions by default</entry>
</row>
+ <row>
+ <entry> <literal>random_seed</literal> </entry>
+ <entry>random generator seed (unless overwritten with <option>-D</option>)</entry>
+ </row>
+
<row>
<entry> <literal>scale</literal> </entry>
<entry>current scale factor</entry>
char *tablespace = NULL;
char *index_tablespace = NULL;
+/* random seed used when calling srandom() */
+int64 random_seed = -1;
+
/*
* end of configurable parameters
*********************************************************************/
" --log-prefix=PREFIX prefix for transaction time log file\n"
" (default: \"pgbench_log\")\n"
" --progress-timestamp use Unix epoch timestamps for progress\n"
+ " --random-seed=SEED set random seed (\"time\", \"rand\", integer)\n"
" --sampling-rate=NUM fraction of transactions to log (e.g., 0.01 for 1%%)\n"
"\nCommon options:\n"
" -d, --debug print debugging output\n"
}
}
+/* call srandom based on some seed. NULL triggers the default behavior. */
+static void
+set_random_seed(const char *seed, const char *origin)
+{
+ /* srandom expects an unsigned int */
+ unsigned int iseed;
+
+ if (seed == NULL || strcmp(seed, "time") == 0)
+ {
+ /* rely on current time */
+ instr_time now;
+ INSTR_TIME_SET_CURRENT(now);
+ iseed = (unsigned int) INSTR_TIME_GET_MICROSEC(now);
+ }
+ else if (strcmp(seed, "rand") == 0)
+ {
+ /* use some "strong" random source */
+ if (!pg_strong_random(&iseed, sizeof(iseed)))
+ {
+ fprintf(stderr, "cannot seed random from a strong source\n");
+ exit(1);
+ }
+ }
+ else
+ {
+ /* parse seed unsigned int value */
+ char garbage;
+ if (sscanf(seed, "%u%c", &iseed, &garbage) != 1)
+ {
+ fprintf(stderr,
+ "error while scanning '%s' from %s, expecting an unsigned integer, 'time' or 'rand'\n",
+ seed, origin);
+ exit(1);
+ }
+ }
+
+ if (seed != NULL)
+ fprintf(stderr, "setting random seed to %u\n", iseed);
+ srandom(iseed);
+ /* no precision loss: 32 bit unsigned int cast to 64 bit int */
+ random_seed = iseed;
+}
+
int
main(int argc, char **argv)
{"progress-timestamp", no_argument, NULL, 6},
{"log-prefix", required_argument, NULL, 7},
{"foreign-keys", no_argument, NULL, 8},
+ {"random-seed", required_argument, NULL, 9},
{NULL, 0, NULL, 0}
};
state = (CState *) pg_malloc(sizeof(CState));
memset(state, 0, sizeof(CState));
+ /* set random seed early, because it may be used while parsing scripts. */
+ set_random_seed(getenv("PGBENCH_RANDOM_SEED"), "PGBENCH_RANDOM_SEED environment variable");
+
while ((c = getopt_long(argc, argv, "iI:h:nvp:dqb:SNc:j:Crs:t:T:U:lf:D:F:M:P:R:L:", long_options, &optindex)) != -1)
{
char *script;
initialization_option_set = true;
foreign_keys = true;
break;
+ case 9: /* random-seed */
+ benchmarking_option_set = true;
+ set_random_seed(optarg, "--random-seed option");
+ break;
default:
fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
exit(1);
exit(1);
}
- /* set random seed */
- INSTR_TIME_SET_CURRENT(start_time);
- srandom((unsigned int) INSTR_TIME_GET_MICROSEC(start_time));
-
if (internal_script_used)
{
/*
if (lookupVariable(&state[0], "client_id") == NULL)
{
for (i = 0; i < nclients; i++)
- {
if (!putVariableInt(&state[i], "startup", "client_id", i))
exit(1);
- }
}
/* set default seed for hash functions */
exit(1);
}
+ /* set random seed unless overwritten */
+ if (lookupVariable(&state[0], "random_seed") == NULL)
+ {
+ for (i = 0; i < nclients; i++)
+ if (!putVariableInt(&state[i], "startup", "random_seed", random_seed))
+ exit(1);
+ }
+
if (!is_no_vacuum)
{
fprintf(stderr, "starting vacuum...");
$filename =~ s/\@\d+$//;
#push @filenames, $filename;
+ # filenames are expected to be unique on a test
+ if (-e $filename)
+ {
+ ok(0, "$filename must not already exists");
+ unlink $filename or die "cannot unlink $filename: $!";
+ }
append_to_file($filename, $$files{$fn});
}
}
} });
# test expressions
+# command 1..3 and 23 depend on random seed which is used to call srandom.
pgbench(
- '-t 1 -Dfoo=-10.1 -Dbla=false -Di=+3 -Dminint=-9223372036854775808 -Dn=null -Dt=t -Df=of -Dd=1.0',
+ '--random-seed=5432 -t 1 -Dfoo=-10.1 -Dbla=false -Di=+3 -Dminint=-9223372036854775808 -Dn=null -Dt=t -Df=of -Dd=1.0',
0,
[ qr{type: .*/001_pgbench_expressions}, qr{processed: 1/1} ],
- [ qr{command=1.: int 1\d\b},
- qr{command=2.: int 1\d\d\b},
- qr{command=3.: int 1\d\d\d\b},
- qr{command=4.: int 4\b},
+ [ qr{setting random seed to 5432\b},
+ # After explicit seeding, the four * random checks (1-3,20) should be
+ # deterministic, but not necessarily portable.
+ qr{command=1.: int 1\d\b}, # uniform random: 12 on linux
+ qr{command=2.: int 1\d\d\b}, # exponential random: 106 on linux
+ qr{command=3.: int 1\d\d\d\b}, # gaussian random: 1462 on linux
+ qr{command=4.: int 4\b},
qr{command=5.: int 5\b},
qr{command=6.: int 6\b},
qr{command=7.: int 7\b},
qr{command=16.: double 16\b},
qr{command=17.: double 17\b},
qr{command=18.: int 9223372036854775807\b},
- qr{command=20.: int [1-9]\b},
+ qr{command=20.: int \d\b}, # zipfian random: 1 on linux
qr{command=21.: double -27\b},
qr{command=22.: double 1024\b},
qr{command=23.: double 1\b},
qr{command=86.: int 86\b},
qr{command=93.: int 93\b},
qr{command=95.: int 0\b},
+ qr{command=96.: int 1\b}, # :scale
+ qr{command=97.: int 0\b}, # :client_id
+ qr{command=98.: int 5432\b}, # :random_seed
],
'pgbench expressions',
{ '001_pgbench_expressions' => q{-- integer functions
\endif
-- must be zero if false branches where skipped
\set nope debug(:nope)
+-- check automatic variables
+\set sc debug(:scale)
+\set ci debug(:client_id)
+\set rs debug(:random_seed)
} });
+# random determinism when seeded
+$node->safe_psql('postgres',
+ 'CREATE UNLOGGED TABLE seeded_random(seed INT8 NOT NULL, rand TEXT NOT NULL, val INTEGER NOT NULL);');
+
+# same value to check for determinism
+my $seed = int(rand(1000000000));
+for my $i (1, 2)
+{
+ pgbench("--random-seed=$seed -t 1",
+ 0,
+ [qr{processed: 1/1}],
+ [qr{setting random seed to $seed\b}],
+ "random seeded with $seed",
+ { "001_pgbench_random_seed_$i" => q{-- test random functions
+\set ur random(1000, 1999)
+\set er random_exponential(2000, 2999, 2.0)
+\set gr random_gaussian(3000, 3999, 3.0)
+\set zr random_zipfian(4000, 4999, 2.5)
+INSERT INTO seeded_random(seed, rand, val) VALUES
+ (:random_seed, 'uniform', :ur),
+ (:random_seed, 'exponential', :er),
+ (:random_seed, 'gaussian', :gr),
+ (:random_seed, 'zipfian', :zr);
+} });
+}
+
+# check that all runs generated the same 4 values
+my ($ret, $out, $err) =
+ $node->psql('postgres',
+ 'SELECT seed, rand, val, COUNT(*) FROM seeded_random GROUP BY seed, rand, val');
+
+ok($ret == 0, "psql seeded_random count ok");
+ok($err eq '', "psql seeded_random count stderr is empty");
+ok($out =~ /\b$seed\|uniform\|1\d\d\d\|2/, "psql seeded_random count uniform");
+ok($out =~ /\b$seed\|exponential\|2\d\d\d\|2/, "psql seeded_random count exponential");
+ok($out =~ /\b$seed\|gaussian\|3\d\d\d\|2/, "psql seeded_random count gaussian");
+ok($out =~ /\b$seed\|zipfian\|4\d\d\d\|2/, "psql seeded_random count zipfian");
+
+$node->safe_psql('postgres', 'DROP TABLE seeded_random;');
+
# backslash commands
pgbench(
'-t 1', 0,
[ 'invalid init step', '-i -I dta',
[qr{unrecognized initialization step},
qr{allowed steps are} ] ],
+ [ 'bad random seed', '--random-seed=one',
+ [qr{error while scanning 'one' from --random-seed option, expecting an unsigned integer} ] ],
# loging sub-options
[ 'sampling => log', '--sampling-rate=0.01',
projects / postgresql / commitdiff