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Add --sampling-rate option to pgbench.

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This allows logging only some fraction of transactions, greatly reducing
the amount of log generated.

Tomas Vondra, reviewed by Robert Haas and Jeff Janes.
This commit is contained in:
Heikki Linnakangas
2012-10-03 15:37:42 +03:00
parent 7ae1815961
commit e1be1df51f
2 changed files with 67 additions and 11 deletions
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54
contrib/pgbench/pgbench.c
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@ -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