<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >pg_stat_statements</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.1.15 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Additional Supplied Modules" HREF="contrib.html"><LINK REL="PREVIOUS" TITLE="pg_standby" HREF="pgstandby.html"><LINK REL="NEXT" TITLE="pgstattuple" HREF="pgstattuple.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2015-02-07T09:47:53"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.1.15 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="pg_standby" HREF="pgstandby.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="contrib.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Appendix F. Additional Supplied Modules</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="pgstattuple" HREF="pgstattuple.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="PGSTATSTATEMENTS" >F.32. pg_stat_statements</A ></H1 ><P > The <TT CLASS="FILENAME" >pg_stat_statements</TT > module provides a means for tracking execution statistics of all SQL statements executed by a server. </P ><P > The module must be loaded by adding <TT CLASS="LITERAL" >pg_stat_statements</TT > to <A HREF="runtime-config-resource.html#GUC-SHARED-PRELOAD-LIBRARIES" >shared_preload_libraries</A > in <TT CLASS="FILENAME" >postgresql.conf</TT >, because it requires additional shared memory. This means that a server restart is needed to add or remove the module. </P ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN141354" >F.32.1. The <TT CLASS="STRUCTNAME" >pg_stat_statements</TT > View</A ></H2 ><P > The statistics gathered by the module are made available via a system view named <TT CLASS="STRUCTNAME" >pg_stat_statements</TT >. This view contains one row for each distinct query text, database ID, and user ID (up to the maximum number of distinct statements that the module can track). The columns of the view are shown in <A HREF="pgstatstatements.html#PGSTATSTATEMENTS-COLUMNS" >Table F-20</A >. </P ><DIV CLASS="TABLE" ><A NAME="PGSTATSTATEMENTS-COLUMNS" ></A ><P ><B >Table F-20. <TT CLASS="STRUCTNAME" >pg_stat_statements</TT > Columns</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><COL><THEAD ><TR ><TH >Name</TH ><TH >Type</TH ><TH >References</TH ><TH >Description</TH ></TR ></THEAD ><TBODY ><TR ><TD ><TT CLASS="STRUCTFIELD" >userid</TT ></TD ><TD ><TT CLASS="TYPE" >oid</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-authid.html" ><TT CLASS="STRUCTNAME" >pg_authid</TT ></A >.oid</TT ></TD ><TD >OID of user who executed the statement</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >dbid</TT ></TD ><TD ><TT CLASS="TYPE" >oid</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-database.html" ><TT CLASS="STRUCTNAME" >pg_database</TT ></A >.oid</TT ></TD ><TD >OID of database in which the statement was executed</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >query</TT ></TD ><TD ><TT CLASS="TYPE" >text</TT ></TD ><TD > </TD ><TD >Text of the statement (up to <A HREF="runtime-config-statistics.html#GUC-TRACK-ACTIVITY-QUERY-SIZE" >track_activity_query_size</A > bytes)</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >calls</TT ></TD ><TD ><TT CLASS="TYPE" >bigint</TT ></TD ><TD > </TD ><TD >Number of times executed</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >total_time</TT ></TD ><TD ><TT CLASS="TYPE" >double precision</TT ></TD ><TD > </TD ><TD >Total time spent in the statement, in seconds</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >rows</TT ></TD ><TD ><TT CLASS="TYPE" >bigint</TT ></TD ><TD > </TD ><TD >Total number of rows retrieved or affected by the statement</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >shared_blks_hit</TT ></TD ><TD ><TT CLASS="TYPE" >bigint</TT ></TD ><TD > </TD ><TD >Total number of shared blocks hits by the statement</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >shared_blks_read</TT ></TD ><TD ><TT CLASS="TYPE" >bigint</TT ></TD ><TD > </TD ><TD >Total number of shared blocks reads by the statement</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >shared_blks_written</TT ></TD ><TD ><TT CLASS="TYPE" >bigint</TT ></TD ><TD > </TD ><TD >Total number of shared blocks writes by the statement</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >local_blks_hit</TT ></TD ><TD ><TT CLASS="TYPE" >bigint</TT ></TD ><TD > </TD ><TD >Total number of local blocks hits by the statement</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >local_blks_read</TT ></TD ><TD ><TT CLASS="TYPE" >bigint</TT ></TD ><TD > </TD ><TD >Total number of local blocks reads by the statement</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >local_blks_written</TT ></TD ><TD ><TT CLASS="TYPE" >bigint</TT ></TD ><TD > </TD ><TD >Total number of local blocks writes by the statement</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >temp_blks_read</TT ></TD ><TD ><TT CLASS="TYPE" >bigint</TT ></TD ><TD > </TD ><TD >Total number of temp blocks reads by the statement</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >temp_blks_written</TT ></TD ><TD ><TT CLASS="TYPE" >bigint</TT ></TD ><TD > </TD ><TD >Total number of temp blocks writes by the statement</TD ></TR ></TBODY ></TABLE ></DIV ><P > This view, and the function <CODE CLASS="FUNCTION" >pg_stat_statements_reset</CODE >, are available only in databases they have been specifically installed into by installing the <TT CLASS="LITERAL" >pg_stat_statements</TT > extension. However, statistics are tracked across all databases of the server whenever the <TT CLASS="FILENAME" >pg_stat_statements</TT > module is loaded into the server, regardless of presence of the view. </P ><P > For security reasons, non-superusers are not allowed to see the text of queries executed by other users. They can see the statistics, however, if the view has been installed in their database. </P ><P > Note that statements are considered the same if they have the same text, regardless of the values of any out-of-line parameters used in the statement. Using out-of-line parameters will help to group statements together and may make the statistics more useful. </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN141482" >F.32.2. Functions</A ></H2 ><P ></P ><DIV CLASS="VARIABLELIST" ><DL ><DT ><CODE CLASS="FUNCTION" >pg_stat_statements_reset() returns void</CODE ></DT ><DD ><P > <CODE CLASS="FUNCTION" >pg_stat_statements_reset</CODE > discards all statistics gathered so far by <TT CLASS="FILENAME" >pg_stat_statements</TT >. By default, this function can only be executed by superusers. </P ></DD ></DL ></DIV ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN141492" >F.32.3. Configuration Parameters</A ></H2 ><P ></P ><DIV CLASS="VARIABLELIST" ><DL ><DT ><TT CLASS="VARNAME" >pg_stat_statements.max</TT > (<TT CLASS="TYPE" >integer</TT >)</DT ><DD ><P > <TT CLASS="VARNAME" >pg_stat_statements.max</TT > is the maximum number of statements tracked by the module (i.e., the maximum number of rows in the <TT CLASS="STRUCTNAME" >pg_stat_statements</TT > view). If more distinct statements than that are observed, information about the least-executed statements is discarded. The default value is 1000. This parameter can only be set at server start. </P ></DD ><DT ><TT CLASS="VARNAME" >pg_stat_statements.track</TT > (<TT CLASS="TYPE" >enum</TT >)</DT ><DD ><P > <TT CLASS="VARNAME" >pg_stat_statements.track</TT > controls which statements are counted by the module. Specify <TT CLASS="LITERAL" >top</TT > to track top-level statements (those issued directly by clients), <TT CLASS="LITERAL" >all</TT > to also track nested statements (such as statements invoked within functions), or <TT CLASS="LITERAL" >none</TT > to disable. The default value is <TT CLASS="LITERAL" >top</TT >. Only superusers can change this setting. </P ></DD ><DT ><TT CLASS="VARNAME" >pg_stat_statements.track_utility</TT > (<TT CLASS="TYPE" >boolean</TT >)</DT ><DD ><P > <TT CLASS="VARNAME" >pg_stat_statements.track_utility</TT > controls whether utility commands are tracked by the module. Utility commands are all those other than <TT CLASS="COMMAND" >SELECT</TT >, <TT CLASS="COMMAND" >INSERT</TT >, <TT CLASS="COMMAND" >UPDATE</TT > and <TT CLASS="COMMAND" >DELETE</TT >. The default value is <TT CLASS="LITERAL" >on</TT >. Only superusers can change this setting. </P ></DD ><DT ><TT CLASS="VARNAME" >pg_stat_statements.save</TT > (<TT CLASS="TYPE" >boolean</TT >)</DT ><DD ><P > <TT CLASS="VARNAME" >pg_stat_statements.save</TT > specifies whether to save statement statistics across server shutdowns. If it is <TT CLASS="LITERAL" >off</TT > then statistics are not saved at shutdown nor reloaded at server start. The default value is <TT CLASS="LITERAL" >on</TT >. This parameter can only be set in the <TT CLASS="FILENAME" >postgresql.conf</TT > file or on the server command line. </P ></DD ></DL ></DIV ><P > The module requires additional shared memory amounting to about <TT CLASS="VARNAME" >pg_stat_statements.max</TT > <TT CLASS="LITERAL" >*</TT > <A HREF="runtime-config-statistics.html#GUC-TRACK-ACTIVITY-QUERY-SIZE" >track_activity_query_size</A > bytes. Note that this memory is consumed whenever the module is loaded, even if <TT CLASS="VARNAME" >pg_stat_statements.track</TT > is set to <TT CLASS="LITERAL" >none</TT >. </P ><P > In order to set any of these parameters in your <TT CLASS="FILENAME" >postgresql.conf</TT > file, you will need to add <TT CLASS="LITERAL" >pg_stat_statements</TT > to <A HREF="runtime-config-custom.html#GUC-CUSTOM-VARIABLE-CLASSES" >custom_variable_classes</A >. Typical usage might be: </P><PRE CLASS="PROGRAMLISTING" ># postgresql.conf shared_preload_libraries = 'pg_stat_statements' custom_variable_classes = 'pg_stat_statements' pg_stat_statements.max = 10000 pg_stat_statements.track = all</PRE ><P> </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN141547" >F.32.4. Sample Output</A ></H2 ><PRE CLASS="SCREEN" >bench=# SELECT pg_stat_statements_reset(); $ pgbench -i bench $ pgbench -c10 -t300 -M prepared bench bench=# \x bench=# SELECT query, calls, total_time, rows, 100.0 * shared_blks_hit / nullif(shared_blks_hit + shared_blks_read, 0) AS hit_percent FROM pg_stat_statements ORDER BY total_time DESC LIMIT 5; -[ RECORD 1 ]--------------------------------------------------------------------- query | UPDATE pgbench_branches SET bbalance = bbalance + $1 WHERE bid = $2; calls | 3000 total_time | 9.60900100000002 rows | 2836 hit_percent | 99.9778970000200936 -[ RECORD 2 ]--------------------------------------------------------------------- query | UPDATE pgbench_tellers SET tbalance = tbalance + $1 WHERE tid = $2; calls | 3000 total_time | 8.015156 rows | 2990 hit_percent | 99.9731126579631345 -[ RECORD 3 ]--------------------------------------------------------------------- query | copy pgbench_accounts from stdin calls | 1 total_time | 0.310624 rows | 100000 hit_percent | 0.30395136778115501520 -[ RECORD 4 ]--------------------------------------------------------------------- query | UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2; calls | 3000 total_time | 0.271741999999997 rows | 3000 hit_percent | 93.7968855088209426 -[ RECORD 5 ]--------------------------------------------------------------------- query | alter table pgbench_accounts add primary key (aid) calls | 1 total_time | 0.08142 rows | 0 hit_percent | 34.4947735191637631</PRE ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN141550" >F.32.5. Author</A ></H2 ><P > Takahiro Itagaki <CODE CLASS="EMAIL" ><<A HREF="mailto:itagaki.takahiro@oss.ntt.co.jp" >itagaki.takahiro@oss.ntt.co.jp</A >></CODE > </P ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="pgstandby.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="pgstattuple.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >pg_standby</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="contrib.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >pgstattuple</TD ></TR ></TABLE ></DIV ></BODY ></HTML >