Hello. The attached patch has made it more feasible for us to gather
profiling data on a production system for analysis with pgFouine. It
has been written against PostgreSQL 8.3.5 and tested on Linux. Comments
welcome.
timo
>From a4d5b489f462ad31b62774ec98af08f184cb0754 Mon Sep 17 00:00:00 2001
From: Timo Savola <timo.savola@dynamoid.com>
Date: Thu, 22 Jan 2009 13:02:10 +0200
Subject: [PATCH] log_duration_sample config option
When used with the log_duration or the log_min_duration_statement option,
it specifies the percentage of statements to log using random sampling.
---
src/backend/tcop/postgres.c | 30 +++++++++++++++++++++++++++---
src/backend/utils/misc/guc.c | 12 ++++++++++++
src/include/utils/guc.h | 2 ++
3 files changed, 41 insertions(+), 3 deletions(-)
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 12ebce4..14f472a 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -22,6 +22,9 @@
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
+#include <byteswap.h>
+#include <endian.h>
+#include <sys/time.h>
#include <sys/socket.h>
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
@@ -2001,6 +2004,8 @@ check_log_statement(List *stmt_list)
int
check_log_duration(char *msec_str, bool was_logged)
{
+ int retval = 0;
+
if (log_duration || log_min_duration_statement >= 0)
{
long secs;
@@ -2028,13 +2033,32 @@ check_log_duration(char *msec_str, bool was_logged)
snprintf(msec_str, 32, "%ld.%03d",
secs * 1000 + msecs, usecs % 1000);
if (exceeded && !was_logged)
- return 2;
+ retval = 2;
else
- return 1;
+ retval = 1;
+ }
+
+ if (retval > 0 && log_duration_sample < 1.0)
+ {
+ static uint64_t seed;
+
+ if (seed == 0)
+ {
+ struct timeval tv;
+
+ gettimeofday(&tv, NULL);
+ seed = (uint64_t) tv.tv_sec * 1000000 + tv.tv_usec;
+#if BYTE_ORDER != LITTLE_ENDIAN
+ bswap_64(seed);
+#endif
+ }
+
+ if (erand48((unsigned short *) &seed) > log_duration_sample)
+ retval = 0;
}
}
- return 0;
+ return retval;
}
/*
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index b1c6e85..1e76cd5 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -225,6 +225,8 @@ int tcp_keepalives_idle;
int tcp_keepalives_interval;
int tcp_keepalives_count;
+double log_duration_sample = 1.0;
+
/*
* These variables are all dummies that don't do anything, except in some
* cases provide the value for SHOW to display. The real state is elsewhere
@@ -1884,6 +1886,16 @@ static struct config_real ConfigureNamesReal[] =
0.5, 0.0, 1.0, NULL, NULL
},
+ {
+ {"log_duration_sample", PGC_SUSET, LOGGING_WHEN,
+ gettext_noop("Sets the sampling frequency (probability) used for "
+ "logging statement durations."),
+ gettext_noop("1.0 prints all queries.")
+ },
+ &log_duration_sample,
+ 1.0, 0.0, 1.0, NULL, NULL
+ },
+
/* End-of-list marker */
{
{NULL, 0, 0, NULL, NULL}, NULL, 0.0, 0.0, 0.0, NULL, NULL
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 49b88f5..fde6a26 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -145,6 +145,8 @@ extern int tcp_keepalives_idle;
extern int tcp_keepalives_interval;
extern int tcp_keepalives_count;
+extern double log_duration_sample;
+
extern void SetConfigOption(const char *name, const char *value,
GucContext context, GucSource source);
--
1.5.6.5