From 75506195da81d75597a4025b72f8367e6c45f60d Mon Sep 17 00:00:00 2001 From: Tomas Vondra 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 c91e3e1550..1f8d1bdb27 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -5850,13 +5850,12 @@ local0.* /var/log/postgresql Causes the duration of each completed statement to be logged if the statement ran for at least the specified number of - milliseconds, modulated by log_statement_sample_rate. - Setting this to zero prints all statement durations. - -1 (the default) disables logging statements due to - exceeding duration threshold; for example, if you set it to - 250ms, 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 250ms + 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. @@ -5882,27 +5881,6 @@ local0.* /var/log/postgresql - - log_statement_sample_rate (real) - - log_statement_sample_rate configuration parameter - - - - - Determines the fraction of statements that exceed - to be logged. - The default is 1.0, meaning log all such - statements. - Setting this to zero disables logging by duration, same as setting - log_min_duration_statement to - -1. - log_statement_sample_rate is helpful when the - traffic is too high to log all queries. - - - - log_transaction_sample_rate (real) diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c index 1679cce1f1..e8d8e6f828 100644 --- a/src/backend/tcop/postgres.c +++ b/src/backend/tcop/postgres.c @@ -2212,8 +2212,7 @@ 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). * @@ -2237,7 +2236,6 @@ check_log_duration(char *msec_str, bool was_logged) int usecs; int msecs; bool exceeded; - bool in_sample; TimestampDifference(GetCurrentStatementStartTimestamp(), GetCurrentTimestamp(), @@ -2254,17 +2252,7 @@ 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 fc463601ff..eb78522053 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 cfad86c02a..65a6da18b3 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 e800230ed9..a93ed77c9c 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;