Revert "Add log_statement_sample_rate parameter"
This reverts commit 88bdbd3f74.
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
This commit is contained in:
Tomas Vondra
parent
4f9ed8f3c5
commit
75506195da
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@ -5850,13 +5850,12 @@ local0.* /var/log/postgresql
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<para>
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Causes the duration of each completed statement to be logged
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if the statement ran for at least the specified number of
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milliseconds, modulated by <varname>log_statement_sample_rate</varname>.
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Setting this to zero prints all statement durations.
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<literal>-1</literal> (the default) disables logging statements due to
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exceeding duration threshold; for example, if you set it to
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<literal>250ms</literal>, then all SQL statements that run 250ms or
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longer will be logged. Enabling this parameter can be helpful in
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tracking down unoptimized queries in your applications.
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milliseconds. Setting this to zero prints all statement durations.
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Minus-one (the default) disables logging statement durations.
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For example, if you set it to <literal>250ms</literal>
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then all SQL statements that run 250ms or longer will be
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logged. Enabling this parameter can be helpful in tracking down
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unoptimized queries in your applications.
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Only superusers can change this setting.
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</para>
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@ -5882,27 +5881,6 @@ local0.* /var/log/postgresql
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</listitem>
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</varlistentry>
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<varlistentry id="guc-log-statement-sample-rate" xreflabel="log_statement_sample_rate">
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<term><varname>log_statement_sample_rate</varname> (<type>real</type>)
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<indexterm>
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<primary><varname>log_statement_sample_rate</varname> configuration parameter</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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Determines the fraction of statements that exceed
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<xref linkend="guc-log-min-duration-statement"/> to be logged.
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The default is <literal>1.0</literal>, meaning log all such
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statements.
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Setting this to zero disables logging by duration, same as setting
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<varname>log_min_duration_statement</varname> to
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<literal>-1</literal>.
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<varname>log_statement_sample_rate</varname> is helpful when the
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traffic is too high to log all queries.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-log-transaction-sample-rate" xreflabel="log_transaction_sample_rate">
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<term><varname>log_transaction_sample_rate</varname> (<type>real</type>)
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<indexterm>
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@ -2212,8 +2212,7 @@ check_log_statement(List *stmt_list)
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/*
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* check_log_duration
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* Determine whether current command's duration should be logged.
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* If log_statement_sample_rate < 1.0, log only a sample.
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* Determine whether current command's duration should be logged
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* We also check if this statement in this transaction must be logged
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* (regardless of its duration).
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*
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@ -2237,7 +2236,6 @@ check_log_duration(char *msec_str, bool was_logged)
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int usecs;
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int msecs;
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bool exceeded;
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bool in_sample;
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TimestampDifference(GetCurrentStatementStartTimestamp(),
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GetCurrentTimestamp(),
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@ -2254,17 +2252,7 @@ check_log_duration(char *msec_str, bool was_logged)
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(secs > log_min_duration_statement / 1000 ||
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secs * 1000 + msecs >= log_min_duration_statement)));
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/*
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* Do not log if log_statement_sample_rate = 0. Log a sample if
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* log_statement_sample_rate <= 1 and avoid unecessary random() call
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* if log_statement_sample_rate = 1.
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*/
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if (exceeded)
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in_sample = log_statement_sample_rate != 0 &&
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(log_statement_sample_rate == 1 ||
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random() <= log_statement_sample_rate * MAX_RANDOM_VALUE);
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if ((exceeded && in_sample) || log_duration || xact_is_sampled)
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if (exceeded || log_duration || xact_is_sampled)
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{
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snprintf(msec_str, 32, "%ld.%03d",
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secs * 1000 + msecs, usecs % 1000);
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@ -511,7 +511,6 @@ int log_min_messages = WARNING;
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int client_min_messages = NOTICE;
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int log_min_duration_statement = -1;
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int log_temp_files = -1;
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double log_statement_sample_rate = 1.0;
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double log_xact_sample_rate = 0;
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int trace_recovery_messages = LOG;
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@ -2705,8 +2704,7 @@ static struct config_int ConfigureNamesInt[] =
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{"log_min_duration_statement", PGC_SUSET, LOGGING_WHEN,
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gettext_noop("Sets the minimum execution time above which "
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"statements will be logged."),
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gettext_noop("Zero prints all queries, subject to log_statement_sample_rate. "
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"-1 turns this feature off."),
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gettext_noop("Zero prints all queries. -1 turns this feature off."),
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GUC_UNIT_MS
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},
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&log_min_duration_statement,
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@ -3432,17 +3430,6 @@ static struct config_real ConfigureNamesReal[] =
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NULL, NULL, NULL
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},
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{
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{"log_statement_sample_rate", PGC_SUSET, LOGGING_WHEN,
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gettext_noop("Fraction of statements exceeding log_min_duration_statement to be logged."),
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gettext_noop("If you only want a sample, use a value between 0.0 (never "
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"log) and 1.0 (always log).")
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},
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&log_statement_sample_rate,
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1.0, 0.0, 1.0,
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NULL, NULL, NULL
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},
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{
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{"log_transaction_sample_rate", PGC_SUSET, LOGGING_WHEN,
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gettext_noop("Set the fraction of transactions to log for new transactions."),
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@ -488,14 +488,10 @@
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# fatal
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# panic (effectively off)
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#log_min_duration_statement = -1 # logs statements and their durations
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# according to log_statement_sample_rate. -1 is disabled,
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# 0 logs all statements, > 0 logs only statements running
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# at least this number of milliseconds.
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#log_statement_sample_rate = 1.0 # Fraction of logged statements exceeding
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# log_min_duration_statement to be logged.
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# 1.0 logs all such statements, 0.0 never logs.
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#log_min_duration_statement = -1 # -1 is disabled, 0 logs all statements
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# and their durations, > 0 logs only
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# statements running at least this number
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# of milliseconds
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#log_transaction_sample_rate = 0.0 # Fraction of transactions whose statements
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# are logged regardless of their duration. 1.0 logs all
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@ -253,7 +253,6 @@ extern PGDLLIMPORT int log_min_messages;
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extern PGDLLIMPORT int client_min_messages;
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extern int log_min_duration_statement;
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extern int log_temp_files;
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extern double log_statement_sample_rate;
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extern double log_xact_sample_rate;
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extern int temp_file_limit;
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