diff --git a/contrib/pgbench/pgbench.c b/contrib/pgbench/pgbench.c
index a669cf406ba0b639cdb24e06aabeeea21f3262f2..c399d59d25b448a92c6b3df23c02d149c2ab5434 100644
--- a/contrib/pgbench/pgbench.c
+++ b/contrib/pgbench/pgbench.c
@@ -129,6 +129,11 @@ int foreign_keys = 0;
*/
int unlogged_tables = 0;
+/*
+ * log sampling rate (1.0 = log everything, 0.0 = option not given)
+ */
+double sample_rate = 0.0;
+
/*
* tablespace selection
*/
@@ -370,6 +375,8 @@ usage(void)
" -f FILENAME read transaction script from FILENAME\n"
" -j NUM number of threads (default: 1)\n"
" -l write transaction times to log file\n"
+ " --sampling-rate NUM\n"
+ " fraction of transactions to log (e.g. 0.01 for 1%% sample)\n"
" -M simple|extended|prepared\n"
" protocol for submitting queries to server (default: simple)\n"
" -n do not run VACUUM before tests\n"
@@ -883,21 +890,30 @@ top:
instr_time diff;
double usec;
- INSTR_TIME_SET_CURRENT(now);
- diff = now;
- INSTR_TIME_SUBTRACT(diff, st->txn_begin);
- usec = (double) INSTR_TIME_GET_MICROSEC(diff);
+ /*
+ * write the log entry if this row belongs to the random sample,
+ * or no sampling rate was given which means log everything.
+ */
+ if (sample_rate == 0.0 ||
+ pg_erand48(thread->random_state) <= sample_rate)
+ {
+
+ INSTR_TIME_SET_CURRENT(now);
+ diff = now;
+ INSTR_TIME_SUBTRACT(diff, st->txn_begin);
+ usec = (double) INSTR_TIME_GET_MICROSEC(diff);
#ifndef WIN32
- /* This is more than we really ought to know about instr_time */
- fprintf(logfile, "%d %d %.0f %d %ld %ld\n",
- st->id, st->cnt, usec, st->use_file,
- (long) now.tv_sec, (long) now.tv_usec);
+ /* This is more than we really ought to know about instr_time */
+ fprintf(logfile, "%d %d %.0f %d %ld %ld\n",
+ st->id, st->cnt, usec, st->use_file,
+ (long) now.tv_sec, (long) now.tv_usec);
#else
- /* On Windows, instr_time doesn't provide a timestamp anyway */
- fprintf(logfile, "%d %d %.0f %d 0 0\n",
- st->id, st->cnt, usec, st->use_file);
+ /* On Windows, instr_time doesn't provide a timestamp anyway */
+ fprintf(logfile, "%d %d %.0f %d 0 0\n",
+ st->id, st->cnt, usec, st->use_file);
#endif
+ }
}
if (commands[st->state]->type == SQL_COMMAND)
@@ -1926,6 +1942,7 @@ main(int argc, char **argv)
{"index-tablespace", required_argument, NULL, 3},
{"tablespace", required_argument, NULL, 2},
{"unlogged-tables", no_argument, &unlogged_tables, 1},
+ {"sampling-rate", required_argument, NULL, 4},
{NULL, 0, NULL, 0}
};
@@ -2131,6 +2148,14 @@ main(int argc, char **argv)
case 3: /* index-tablespace */
index_tablespace = optarg;
break;
+ case 4:
+ sample_rate = atof(optarg);
+ if (sample_rate <= 0.0 || sample_rate > 1.0)
+ {
+ fprintf(stderr, "invalid sampling rate: %f\n", sample_rate);
+ exit(1);
+ }
+ break;
default:
fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
exit(1);
@@ -2166,6 +2191,13 @@ main(int argc, char **argv)
exit(1);
}
+ /* --sampling-rate may be used only with -l */
+ if (sample_rate > 0.0 && !use_log)
+ {
+ fprintf(stderr, "log sampling rate is allowed only when logging transactions (-l) \n");
+ exit(1);
+ }
+
/*
* is_latencies only works with multiple threads in thread-based
* implementations, not fork-based ones, because it supposes that the
diff --git a/doc/src/sgml/pgbench.sgml b/doc/src/sgml/pgbench.sgml
index 437fceab2e482e9821e09be3e8e988e18c2289cd..91530abe5b0ab737ca944bed6712760d1d84aae3 100644
--- a/doc/src/sgml/pgbench.sgml
+++ b/doc/src/sgml/pgbench.sgml
@@ -316,6 +316,24 @@ pgbench <optional> <replaceable>options</> </optional> <replaceable>dbname</>
</listitem>
</varlistentry>
+ <varlistentry>
+ <term><option>--sampling-rate</option> <replaceable>rate</></term>
+ <listitem>
+ <para>
+ Sampling rate, used when writing data into the log, to reduce the
+ amount of log generated. If this option is given, only the specified
+ fraction of transactions are logged. 1.0 means all transactions will
+ be logged, 0.05 means only 5% of the transactions will be logged.
+ </para>
+ <para>
+ Remember to take the sampling rate into account when processing the
+ log file. For example, when computing tps values, you need to multiply
+ the numbers accordingly (e.g. with 0.01 sample rate, you'll only get
+ 1/100 of the actual tps).
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term><option>-M</option> <replaceable>querymode</></term>
<listitem>
@@ -750,6 +768,12 @@ END;
0 201 2513 0 1175850569 608
0 202 2038 0 1175850569 2663
</screen></para>
+
+ <para>
+ When running a long test on hardware that can handle a lot of transactions,
+ the log files can become very large. The <option>--sampling-rate</> option
+ can be used to log only a random sample of transactions.
+ </para>
</refsect2>
<refsect2>