From d5f53a8e26caf7931db6ad3939cd34d36ea54d91 Mon Sep 17 00:00:00 2001
From: Tomas Vondra <tomas.vondra@postgresql.org>
Date: Sun, 4 Aug 2019 20:29:00 +0200
Subject: [PATCH] Revert "Add log_statement_sample_rate parameter"
This reverts commit 88bdbd3f746049834ae3cc972e6e650586ec3c9d.
As committed, statement sampling used the existing duration threshold
(log_min_duration_statement) when decide which statements to sample.
The issue is that even the longest statements are subject to sampling,
and so may not end up logged. An improvement was proposed, introducing
a second duration threshold, but it would not be backwards compatible.
So we've decided to revert this feature - the separate threshold should
be part of the feature itself.
Discussion: https://postgr.es/m/CAFj8pRDS8tQ3Wviw9%3DAvODyUciPSrGeMhJi_WPE%2BEB8%2B4gLL-Q%40mail.gmail.com
---
doc/src/sgml/config.sgml | 34 ++++---------------
src/backend/tcop/postgres.c | 16 ++-------
src/backend/utils/misc/guc.c | 15 +-------
src/backend/utils/misc/postgresql.conf.sample | 12 +++----
src/include/utils/guc.h | 1 -
5 files changed, 13 insertions(+), 65 deletions(-)
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index c91e3e15507..1f8d1bdb27d 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5850,13 +5850,12 @@ local0.* /var/log/postgresql
<para>
Causes the duration of each completed statement to be logged
if the statement ran for at least the specified number of
- milliseconds, modulated by <varname>log_statement_sample_rate</varname>.
- Setting this to zero prints all statement durations.
- <literal>-1</literal> (the default) disables logging statements due to
- exceeding duration threshold; for example, if you set it to
- <literal>250ms</literal>, then all SQL statements that run 250ms or
- longer will be logged. Enabling this parameter can be helpful in
- tracking down unoptimized queries in your applications.
+ milliseconds. Setting this to zero prints all statement durations.
+ Minus-one (the default) disables logging statement durations.
+ For example, if you set it to <literal>250ms</literal>
+ then all SQL statements that run 250ms or longer will be
+ logged. Enabling this parameter can be helpful in tracking down
+ unoptimized queries in your applications.
Only superusers can change this setting.
</para>
@@ -5882,27 +5881,6 @@ local0.* /var/log/postgresql
</listitem>
</varlistentry>
- <varlistentry id="guc-log-statement-sample-rate" xreflabel="log_statement_sample_rate">
- <term><varname>log_statement_sample_rate</varname> (<type>real</type>)
- <indexterm>
- <primary><varname>log_statement_sample_rate</varname> configuration parameter</primary>
- </indexterm>
- </term>
- <listitem>
- <para>
- Determines the fraction of statements that exceed
- <xref linkend="guc-log-min-duration-statement"/> to be logged.
- The default is <literal>1.0</literal>, meaning log all such
- statements.
- Setting this to zero disables logging by duration, same as setting
- <varname>log_min_duration_statement</varname> to
- <literal>-1</literal>.
- <varname>log_statement_sample_rate</varname> is helpful when the
- traffic is too high to log all queries.
- </para>
- </listitem>
- </varlistentry>
-
<varlistentry id="guc-log-transaction-sample-rate" xreflabel="log_transaction_sample_rate">
<term><varname>log_transaction_sample_rate</varname> (<type>real</type>)
<indexterm>
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index f010aa884ce..c28cc370129 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -2192,8 +2192,7 @@ check_log_statement(List *stmt_list)
/*
* check_log_duration
- * Determine whether current command's duration should be logged.
- * If log_statement_sample_rate < 1.0, log only a sample.
+ * Determine whether current command's duration should be logged
* We also check if this statement in this transaction must be logged
* (regardless of its duration).
*
@@ -2217,7 +2216,6 @@ check_log_duration(char *msec_str, bool was_logged)
int usecs;
int msecs;
bool exceeded;
- bool in_sample;
TimestampDifference(GetCurrentStatementStartTimestamp(),
GetCurrentTimestamp(),
@@ -2234,17 +2232,7 @@ check_log_duration(char *msec_str, bool was_logged)
(secs > log_min_duration_statement / 1000 ||
secs * 1000 + msecs >= log_min_duration_statement)));
- /*
- * Do not log if log_statement_sample_rate = 0. Log a sample if
- * log_statement_sample_rate <= 1 and avoid unecessary random() call
- * if log_statement_sample_rate = 1.
- */
- if (exceeded)
- in_sample = log_statement_sample_rate != 0 &&
- (log_statement_sample_rate == 1 ||
- random() <= log_statement_sample_rate * MAX_RANDOM_VALUE);
-
- if ((exceeded && in_sample) || log_duration || xact_is_sampled)
+ if (exceeded || log_duration || xact_is_sampled)
{
snprintf(msec_str, 32, "%ld.%03d",
secs * 1000 + msecs, usecs % 1000);
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 631f16f5fe7..8adb1cfeab0 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -511,7 +511,6 @@ int log_min_messages = WARNING;
int client_min_messages = NOTICE;
int log_min_duration_statement = -1;
int log_temp_files = -1;
-double log_statement_sample_rate = 1.0;
double log_xact_sample_rate = 0;
int trace_recovery_messages = LOG;
@@ -2705,8 +2704,7 @@ static struct config_int ConfigureNamesInt[] =
{"log_min_duration_statement", PGC_SUSET, LOGGING_WHEN,
gettext_noop("Sets the minimum execution time above which "
"statements will be logged."),
- gettext_noop("Zero prints all queries, subject to log_statement_sample_rate. "
- "-1 turns this feature off."),
+ gettext_noop("Zero prints all queries. -1 turns this feature off."),
GUC_UNIT_MS
},
&log_min_duration_statement,
@@ -3432,17 +3430,6 @@ static struct config_real ConfigureNamesReal[] =
NULL, NULL, NULL
},
- {
- {"log_statement_sample_rate", PGC_SUSET, LOGGING_WHEN,
- gettext_noop("Fraction of statements exceeding log_min_duration_statement to be logged."),
- gettext_noop("If you only want a sample, use a value between 0.0 (never "
- "log) and 1.0 (always log).")
- },
- &log_statement_sample_rate,
- 1.0, 0.0, 1.0,
- NULL, NULL, NULL
- },
-
{
{"log_transaction_sample_rate", PGC_SUSET, LOGGING_WHEN,
gettext_noop("Set the fraction of transactions to log for new transactions."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 5ee5e09ddf6..072dfb6f0d6 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -488,14 +488,10 @@
# fatal
# panic (effectively off)
-#log_min_duration_statement = -1 # logs statements and their durations
- # according to log_statement_sample_rate. -1 is disabled,
- # 0 logs all statements, > 0 logs only statements running
- # at least this number of milliseconds.
-
-#log_statement_sample_rate = 1.0 # Fraction of logged statements exceeding
- # log_min_duration_statement to be logged.
- # 1.0 logs all such statements, 0.0 never logs.
+#log_min_duration_statement = -1 # -1 is disabled, 0 logs all statements
+ # and their durations, > 0 logs only
+ # statements running at least this number
+ # of milliseconds
#log_transaction_sample_rate = 0.0 # Fraction of transactions whose statements
# are logged regardless of their duration. 1.0 logs all
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index e800230ed94..a93ed77c9c3 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -253,7 +253,6 @@ extern PGDLLIMPORT int log_min_messages;
extern PGDLLIMPORT int client_min_messages;
extern int log_min_duration_statement;
extern int log_temp_files;
-extern double log_statement_sample_rate;
extern double log_xact_sample_rate;
extern int temp_file_limit;
--
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