diff options
| -rw-r--r-- | doc/src/sgml/config.sgml | 97 | ||||
| -rw-r--r-- | src/backend/nodes/params.c | 11 | ||||
| -rw-r--r-- | src/backend/utils/mb/stringinfo_mb.c | 2 |
3 files changed, 49 insertions, 61 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index c1128f89ec7..371d7838fb6 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -5984,13 +5984,13 @@ local0.* /var/log/postgresql <para> Causes the duration of each completed statement to be logged if the statement ran for at least the specified amount of time. - If this value is specified without units, it is taken as 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. + If this value is specified without units, it is taken as milliseconds. + Setting this to zero prints all statement durations. + Minus-one (the default) disables logging statement durations. Only superusers can change this setting. </para> @@ -6030,49 +6030,39 @@ local0.* /var/log/postgresql </term> <listitem> <para> - Allows to sample the logging of the duration of each completed - statement if the statement ran for at least the specified amount of - time. If this value is specified without units, it is taken as milliseconds. + Allows sampling the duration of completed statements that ran for + at least the specified amount of time. This produces the same + kind of log entries as + <xref linkend="guc-log-min-duration-statement"/>, but only for a + subset of the executed statements, with sample rate controlled by + <xref linkend="guc-log-statement-sample-rate"/>. + For example, if you set it to <literal>100ms</literal> then all + SQL statements that run 100ms or longer will be considered for + sampling. Enabling this parameter can be helpful when the + traffic is too high to log all queries. + If this value is specified without units, it is taken as milliseconds. Setting this to zero samples all statement durations. Minus-one (the default) disables sampling statement durations. - For example, if you set it to <literal>250ms</literal> - then all SQL statements that run 250ms or longer will be considered - for sampling, with sample rate is controlled by <xref linkend="guc-log-statement-sample-rate"/>. - Enabling this parameter can be helpful when the traffic too high to - sample all queries. Only superusers can change this setting. </para> <para> - This option has lower priority than <xref linkend="guc-log-min-duration-statement"/>, - meaning that statements with durations exceeding <xref linkend="guc-log-min-duration-statement"/> - are not subject to sampling and are always logged. - </para> - - <para> - For clients using extended query protocol, durations of the Parse, - Bind, and Execute steps are logged independently. + This setting has lower priority + than <varname>log_min_duration_statement</varname>, meaning that + statements with durations + exceeding <varname>log_min_duration_statement</varname> are not + subject to sampling and are always logged. </para> - <note> <para> - When using this option together with - <xref linkend="guc-log-statement"/>, - the text of statements that are logged because of - <varname>log_statement</varname> will not be repeated in the - duration log message. - If you are not using <application>syslog</application>, it is recommended - that you log the PID or session ID using - <xref linkend="guc-log-line-prefix"/> - so that you can link the statement message to the later - duration message using the process ID or session ID. + Other notes for <varname>log_min_duration_statement</varname> + apply also to this setting. </para> - </note> </listitem> </varlistentry> <varlistentry id="guc-log-statement-sample-rate" xreflabel="log_statement_sample_rate"> - <term><varname>log_statement_sample_rate</varname> (<type>real</type>) + <term><varname>log_statement_sample_rate</varname> (<type>floating point</type>) <indexterm> <primary><varname>log_statement_sample_rate</varname> configuration parameter</primary> </indexterm> @@ -6080,43 +6070,40 @@ local0.* /var/log/postgresql <listitem> <para> Determines the fraction of statements with duration exceeding - <xref linkend="guc-log-min-duration-sample"/> to be logged. - This is a statistical parameter, for example <literal>0.5</literal> - means there is statistically one in two chances to log the statement. - The default is <literal>1.0</literal>, meaning log all such + <xref linkend="guc-log-min-duration-sample"/> that will be logged. + Sampling is stochastic, for example <literal>0.5</literal> means + there is statistically one chance in two that any given statement + will be logged. + The default is <literal>1.0</literal>, meaning to log all sampled statements. - Setting this to zero disables sampling logging, same as setting + Setting this to zero disables sampled statement-duration logging, + the same as setting <varname>log_min_duration_sample</varname> to <literal>-1</literal>. - <varname>log_statement_sample_rate</varname> is helpful when the - traffic is too high to log all queries. Only superusers can change this setting. </para> - <note> - <para> - Like all statement-logging options, this option can add significant - overhead. - </para> - </note> </listitem> </varlistentry> <varlistentry id="guc-log-transaction-sample-rate" xreflabel="log_transaction_sample_rate"> - <term><varname>log_transaction_sample_rate</varname> (<type>real</type>) + <term><varname>log_transaction_sample_rate</varname> (<type>floating point</type>) <indexterm> <primary><varname>log_transaction_sample_rate</varname> configuration parameter</primary> </indexterm> </term> <listitem> <para> - Set the fraction of transactions whose statements are all logged, + Sets the fraction of transactions whose statements are all logged, in addition to statements logged for other reasons. It applies to each new transaction regardless of its statements' durations. - The default is <literal>0</literal>, meaning not to log statements - from any additional transaction. Setting this to <literal>1</literal> - logs all statements for all transactions. - <varname>log_transaction_sample_rate</varname> is helpful to track a - sample of transaction. + Sampling is stochastic, for example <literal>0.1</literal> means + there is statistically one chance in ten that any given transaction + will be logged. + <varname>log_transaction_sample_rate</varname> can be helpful to + construct a sample of transactions. + The default is <literal>0</literal>, meaning not to log + statements from any additional transactions. Setting this + to <literal>1</literal> logs all statements of all transactions. Only superusers can change this setting. </para> <note> @@ -6632,9 +6619,9 @@ log_line_prefix = '%m [%p] %q%u@%d/%a ' <para> Controls whether bind parameters are logged when a statement is logged as a result of <xref linkend="guc-log-min-error-statement"/>. - It adds some overhead, as postgres will compute and store textual - representations of parameter values in memory for all statements, - even if they eventually do not get logged. + It adds some overhead, as <productname>PostgreSQL</productname> will + compute and store textual representations of parameter values in + memory for all statements, even if they eventually do not get logged. This setting has no effect on statements logged due to <xref linkend="guc-log-min-duration-statement"/> or <xref linkend="guc-log-statement"/> settings, as they are always logged diff --git a/src/backend/nodes/params.c b/src/backend/nodes/params.c index b28ec3b6ce4..a57f9eea768 100644 --- a/src/backend/nodes/params.c +++ b/src/backend/nodes/params.c @@ -262,16 +262,16 @@ RestoreParamList(char **start_address) /* * BuildParamLogString - * Return a string that represent the parameter list, for logging. + * Return a string that represents the parameter list, for logging. * * If caller already knows textual representations for some parameters, it can * pass an array of exactly params->numParams values as knownTextValues, which * can contain NULLs for any unknown individual values. NULL can be given if * no parameters are known. * - * If maxlen is not zero, that's the maximum number of characters of the - * input string printed; an ellipsis is added if more characters exist. - * (Added quotes are not considered.) + * If maxlen is not zero, that's the maximum number of bytes of any one + * parameter value to be printed; an ellipsis is added if the string is + * longer. (Added quotes are not considered in this calculation.) */ char * BuildParamLogString(ParamListInfo params, char **knownTextValues, int maxlen) @@ -282,7 +282,8 @@ BuildParamLogString(ParamListInfo params, char **knownTextValues, int maxlen) /* * NB: think not of returning params->paramValuesStr! It may have been - * generated with a different maxlen, and so unsuitable. + * generated with a different maxlen, and so be unsuitable. Besides that, + * this is the function used to create that string. */ /* diff --git a/src/backend/utils/mb/stringinfo_mb.c b/src/backend/utils/mb/stringinfo_mb.c index c153b770076..791a667daea 100644 --- a/src/backend/utils/mb/stringinfo_mb.c +++ b/src/backend/utils/mb/stringinfo_mb.c @@ -26,7 +26,7 @@ /* * appendStringInfoStringQuoted * - * Append up to maxlen characters from s to str, or the whole input string if + * Append up to maxlen bytes from s to str, or the whole input string if * maxlen <= 0, adding single quotes around it and doubling all single quotes. * Add an ellipsis if the copy is incomplete. */ |