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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>F.32. pg_stat_statements</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="pgrowlocks.html" title="F.31. pgrowlocks" /><link rel="next" href="pgstattuple.html" title="F.33. pgstattuple" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">F.32. pg_stat_statements</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="pgrowlocks.html" title="F.31. pgrowlocks">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules">Up</a></td><th width="60%" align="center">Appendix F. Additional Supplied Modules</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.7 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="pgstattuple.html" title="F.33. pgstattuple">Next</a></td></tr></table><hr /></div><div class="sect1" id="PGSTATSTATEMENTS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">F.32. pg_stat_statements</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="pgstatstatements.html#id-1.11.7.41.6">F.32.1. The <code class="structname">pg_stat_statements</code> View</a></span></dt><dt><span class="sect2"><a href="pgstatstatements.html#id-1.11.7.41.7">F.32.2. The <code class="structname">pg_stat_statements_info</code> View</a></span></dt><dt><span class="sect2"><a href="pgstatstatements.html#id-1.11.7.41.8">F.32.3. Functions</a></span></dt><dt><span class="sect2"><a href="pgstatstatements.html#id-1.11.7.41.9">F.32.4. Configuration Parameters</a></span></dt><dt><span class="sect2"><a href="pgstatstatements.html#id-1.11.7.41.10">F.32.5. Sample Output</a></span></dt><dt><span class="sect2"><a href="pgstatstatements.html#id-1.11.7.41.11">F.32.6. Authors</a></span></dt></dl></div><a id="id-1.11.7.41.2" class="indexterm"></a><p>
The <code class="filename">pg_stat_statements</code> module provides a means for
tracking planning and execution statistics of all SQL statements executed by
a server.
</p><p>
The module must be loaded by adding <code class="literal">pg_stat_statements</code> to
<a class="xref" href="runtime-config-client.html#GUC-SHARED-PRELOAD-LIBRARIES">shared_preload_libraries</a> in
<code class="filename">postgresql.conf</code>, because it requires additional shared memory.
This means that a server restart is needed to add or remove the module.
In addition, query identifier calculation must be enabled in order for the
module to be active, which is done automatically if <a class="xref" href="runtime-config-statistics.html#GUC-COMPUTE-QUERY-ID">compute_query_id</a>
is set to <code class="literal">auto</code> or <code class="literal">on</code>, or any third-party
module that calculates query identifiers is loaded.
</p><p>
When <code class="filename">pg_stat_statements</code> is active, it tracks
statistics across all databases of the server. To access and manipulate
these statistics, the module provides views
<code class="structname">pg_stat_statements</code> and
<code class="structname">pg_stat_statements_info</code>,
and the utility functions <code class="function">pg_stat_statements_reset</code> and
<code class="function">pg_stat_statements</code>. These are not available globally but
can be enabled for a specific database with
<code class="command">CREATE EXTENSION pg_stat_statements</code>.
</p><div class="sect2" id="id-1.11.7.41.6"><div class="titlepage"><div><div><h3 class="title">F.32.1. The <code class="structname">pg_stat_statements</code> View</h3></div></div></div><p>
The statistics gathered by the module are made available via a
view named <code class="structname">pg_stat_statements</code>. This view
contains one row for each distinct combination of database ID, user
ID, query ID and whether it's a top-level statement or not (up to
the maximum number of distinct statements that the module can track).
The columns of the view are shown in
<a class="xref" href="pgstatstatements.html#PGSTATSTATEMENTS-COLUMNS" title="Table F.20. pg_stat_statements Columns">Table F.20</a>.
</p><div class="table" id="PGSTATSTATEMENTS-COLUMNS"><p class="title"><strong>Table F.20. <code class="structname">pg_stat_statements</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_stat_statements Columns" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
Column Type
</p>
<p>
Description
</p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">userid</code> <code class="type">oid</code>
(references <a class="link" href="catalog-pg-authid.html" title="53.8. pg_authid"><code class="structname">pg_authid</code></a>.<code class="structfield">oid</code>)
</p>
<p>
OID of user who executed the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">dbid</code> <code class="type">oid</code>
(references <a class="link" href="catalog-pg-database.html" title="53.15. pg_database"><code class="structname">pg_database</code></a>.<code class="structfield">oid</code>)
</p>
<p>
OID of database in which the statement was executed
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">toplevel</code> <code class="type">bool</code>
</p>
<p>
True if the query was executed as a top-level statement
(always true if <code class="varname">pg_stat_statements.track</code> is set to
<code class="literal">top</code>)
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">queryid</code> <code class="type">bigint</code>
</p>
<p>
Hash code to identify identical normalized queries.
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">query</code> <code class="type">text</code>
</p>
<p>
Text of a representative statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">plans</code> <code class="type">bigint</code>
</p>
<p>
Number of times the statement was planned
(if <code class="varname">pg_stat_statements.track_planning</code> is enabled,
otherwise zero)
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">total_plan_time</code> <code class="type">double precision</code>
</p>
<p>
Total time spent planning the statement, in milliseconds
(if <code class="varname">pg_stat_statements.track_planning</code> is enabled,
otherwise zero)
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">min_plan_time</code> <code class="type">double precision</code>
</p>
<p>
Minimum time spent planning the statement, in milliseconds
(if <code class="varname">pg_stat_statements.track_planning</code> is enabled,
otherwise zero)
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">max_plan_time</code> <code class="type">double precision</code>
</p>
<p>
Maximum time spent planning the statement, in milliseconds
(if <code class="varname">pg_stat_statements.track_planning</code> is enabled,
otherwise zero)
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">mean_plan_time</code> <code class="type">double precision</code>
</p>
<p>
Mean time spent planning the statement, in milliseconds
(if <code class="varname">pg_stat_statements.track_planning</code> is enabled,
otherwise zero)
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">stddev_plan_time</code> <code class="type">double precision</code>
</p>
<p>
Population standard deviation of time spent planning the statement,
in milliseconds
(if <code class="varname">pg_stat_statements.track_planning</code> is enabled,
otherwise zero)
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">calls</code> <code class="type">bigint</code>
</p>
<p>
Number of times the statement was executed
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">total_exec_time</code> <code class="type">double precision</code>
</p>
<p>
Total time spent executing the statement, in milliseconds
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">min_exec_time</code> <code class="type">double precision</code>
</p>
<p>
Minimum time spent executing the statement, in milliseconds
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">max_exec_time</code> <code class="type">double precision</code>
</p>
<p>
Maximum time spent executing the statement, in milliseconds
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">mean_exec_time</code> <code class="type">double precision</code>
</p>
<p>
Mean time spent executing the statement, in milliseconds
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">stddev_exec_time</code> <code class="type">double precision</code>
</p>
<p>
Population standard deviation of time spent executing the statement, in milliseconds
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">rows</code> <code class="type">bigint</code>
</p>
<p>
Total number of rows retrieved or affected by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">shared_blks_hit</code> <code class="type">bigint</code>
</p>
<p>
Total number of shared block cache hits by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">shared_blks_read</code> <code class="type">bigint</code>
</p>
<p>
Total number of shared blocks read by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">shared_blks_dirtied</code> <code class="type">bigint</code>
</p>
<p>
Total number of shared blocks dirtied by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">shared_blks_written</code> <code class="type">bigint</code>
</p>
<p>
Total number of shared blocks written by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">local_blks_hit</code> <code class="type">bigint</code>
</p>
<p>
Total number of local block cache hits by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">local_blks_read</code> <code class="type">bigint</code>
</p>
<p>
Total number of local blocks read by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">local_blks_dirtied</code> <code class="type">bigint</code>
</p>
<p>
Total number of local blocks dirtied by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">local_blks_written</code> <code class="type">bigint</code>
</p>
<p>
Total number of local blocks written by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">temp_blks_read</code> <code class="type">bigint</code>
</p>
<p>
Total number of temp blocks read by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">temp_blks_written</code> <code class="type">bigint</code>
</p>
<p>
Total number of temp blocks written by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">blk_read_time</code> <code class="type">double precision</code>
</p>
<p>
Total time the statement spent reading data file blocks, in milliseconds
(if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled, otherwise zero)
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">blk_write_time</code> <code class="type">double precision</code>
</p>
<p>
Total time the statement spent writing data file blocks, in milliseconds
(if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled, otherwise zero)
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">temp_blk_read_time</code> <code class="type">double precision</code>
</p>
<p>
Total time the statement spent reading temporary file blocks, in
milliseconds (if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled,
otherwise zero)
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">temp_blk_write_time</code> <code class="type">double precision</code>
</p>
<p>
Total time the statement spent writing temporary file blocks, in
milliseconds (if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled,
otherwise zero)
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">wal_records</code> <code class="type">bigint</code>
</p>
<p>
Total number of WAL records generated by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">wal_fpi</code> <code class="type">bigint</code>
</p>
<p>
Total number of WAL full page images generated by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">wal_bytes</code> <code class="type">numeric</code>
</p>
<p>
Total amount of WAL generated by the statement in bytes
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">jit_functions</code> <code class="type">bigint</code>
</p>
<p>
Total number of functions JIT-compiled by the statement
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">jit_generation_time</code> <code class="type">double precision</code>
</p>
<p>
Total time spent by the statement on generating JIT code, in milliseconds
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">jit_inlining_count</code> <code class="type">bigint</code>
</p>
<p>
Number of times functions have been inlined
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">jit_inlining_time</code> <code class="type">double precision</code>
</p>
<p>
Total time spent by the statement on inlining functions, in milliseconds
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">jit_optimization_count</code> <code class="type">bigint</code>
</p>
<p>
Number of times the statement has been optimized
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">jit_optimization_time</code> <code class="type">double precision</code>
</p>
<p>
Total time spent by the statement on optimizing, in milliseconds
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">jit_emission_count</code> <code class="type">bigint</code>
</p>
<p>
Number of times code has been emitted
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">jit_emission_time</code> <code class="type">double precision</code>
</p>
<p>
Total time spent by the statement on emitting code, in milliseconds
</p></td></tr></tbody></table></div></div><br class="table-break" /><p>
For security reasons, only superusers and roles with privileges of the
<code class="literal">pg_read_all_stats</code> role are allowed to see the SQL text and
<code class="structfield">queryid</code> of queries executed by other users.
Other users can see the statistics, however, if the view has been installed
in their database.
</p><p>
Plannable queries (that is, <code class="command">SELECT</code>, <code class="command">INSERT</code>,
<code class="command">UPDATE</code>, <code class="command">DELETE</code>, and <code class="command">MERGE</code>) are combined into a single
<code class="structname">pg_stat_statements</code> entry whenever they have identical query
structures according to an internal hash calculation. Typically, two
queries will be considered the same for this purpose if they are
semantically equivalent except for the values of literal constants
appearing in the query. Utility commands (that is, all other commands)
are compared strictly on the basis of their textual query strings, however.
</p><div class="note"><h3 class="title">Note</h3><p>
The following details about constant replacement and
<code class="structfield">queryid</code> only apply when <a class="xref" href="runtime-config-statistics.html#GUC-COMPUTE-QUERY-ID">compute_query_id</a> is enabled. If you use an external
module instead to compute <code class="structfield">queryid</code>, you
should refer to its documentation for details.
</p></div><p>
When a constant's value has been ignored for purposes of matching the query
to other queries, the constant is replaced by a parameter symbol, such
as <code class="literal">$1</code>, in the <code class="structname">pg_stat_statements</code>
display.
The rest of the query text is that of the first query that had the
particular <code class="structfield">queryid</code> hash value associated with the
<code class="structname">pg_stat_statements</code> entry.
</p><p>
In some cases, queries with visibly different texts might get merged into a
single <code class="structname">pg_stat_statements</code> entry. Normally this will happen
only for semantically equivalent queries, but there is a small chance of
hash collisions causing unrelated queries to be merged into one entry.
(This cannot happen for queries belonging to different users or databases,
however.)
</p><p>
Since the <code class="structfield">queryid</code> hash value is computed on the
post-parse-analysis representation of the queries, the opposite is
also possible: queries with identical texts might appear as
separate entries, if they have different meanings as a result of
factors such as different <code class="varname">search_path</code> settings.
</p><p>
Consumers of <code class="structname">pg_stat_statements</code> may wish to use
<code class="structfield">queryid</code> (perhaps in combination with
<code class="structfield">dbid</code> and <code class="structfield">userid</code>) as a more stable
and reliable identifier for each entry than its query text.
However, it is important to understand that there are only limited
guarantees around the stability of the <code class="structfield">queryid</code> hash
value. Since the identifier is derived from the
post-parse-analysis tree, its value is a function of, among other
things, the internal object identifiers appearing in this representation.
This has some counterintuitive implications. For example,
<code class="filename">pg_stat_statements</code> will consider two apparently-identical
queries to be distinct, if they reference a table that was dropped
and recreated between the executions of the two queries.
The hashing process is also sensitive to differences in
machine architecture and other facets of the platform.
Furthermore, it is not safe to assume that <code class="structfield">queryid</code>
will be stable across major versions of <span class="productname">PostgreSQL</span>.
</p><p>
Two servers participating in replication based on physical WAL replay can
be expected to have identical <code class="structfield">queryid</code> values for
the same query. However, logical replication schemes do not promise to
keep replicas identical in all relevant details, so
<code class="structfield">queryid</code> will not be a useful identifier for
accumulating costs across a set of logical replicas.
If in doubt, direct testing is recommended.
</p><p>
Generally, it can be assumed that <code class="structfield">queryid</code> values
are stable between minor version releases of <span class="productname">PostgreSQL</span>,
providing that instances are running on the same machine architecture and
the catalog metadata details match. Compatibility will only be broken
between minor versions as a last resort.
</p><p>
The parameter symbols used to replace constants in
representative query texts start from the next number after the
highest <code class="literal">$</code><em class="replaceable"><code>n</code></em> parameter in the original query
text, or <code class="literal">$1</code> if there was none. It's worth noting that in
some cases there may be hidden parameter symbols that affect this
numbering. For example, <span class="application">PL/pgSQL</span> uses hidden parameter
symbols to insert values of function local variables into queries, so that
a <span class="application">PL/pgSQL</span> statement like <code class="literal">SELECT i + 1 INTO j</code>
would have representative text like <code class="literal">SELECT i + $2</code>.
</p><p>
The representative query texts are kept in an external disk file, and do
not consume shared memory. Therefore, even very lengthy query texts can
be stored successfully. However, if many long query texts are
accumulated, the external file might grow unmanageably large. As a
recovery method if that happens, <code class="filename">pg_stat_statements</code> may
choose to discard the query texts, whereupon all existing entries in
the <code class="structname">pg_stat_statements</code> view will show
null <code class="structfield">query</code> fields, though the statistics associated with
each <code class="structfield">queryid</code> are preserved. If this happens, consider
reducing <code class="varname">pg_stat_statements.max</code> to prevent
recurrences.
</p><p>
<code class="structfield">plans</code> and <code class="structfield">calls</code> aren't
always expected to match because planning and execution statistics are
updated at their respective end phase, and only for successful operations.
For example, if a statement is successfully planned but fails during
the execution phase, only its planning statistics will be updated.
If planning is skipped because a cached plan is used, only its execution
statistics will be updated.
</p></div><div class="sect2" id="id-1.11.7.41.7"><div class="titlepage"><div><div><h3 class="title">F.32.2. The <code class="structname">pg_stat_statements_info</code> View</h3></div></div></div><a id="id-1.11.7.41.7.2" class="indexterm"></a><p>
The statistics of the <code class="filename">pg_stat_statements</code> module
itself are tracked and made available via a view named
<code class="structname">pg_stat_statements_info</code>. This view contains
only a single row. The columns of the view are shown in
<a class="xref" href="pgstatstatements.html#PGSTATSTATEMENTSINFO-COLUMNS" title="Table F.21. pg_stat_statements_info Columns">Table F.21</a>.
</p><div class="table" id="PGSTATSTATEMENTSINFO-COLUMNS"><p class="title"><strong>Table F.21. <code class="structname">pg_stat_statements_info</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_stat_statements_info Columns" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
Column Type
</p>
<p>
Description
</p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">dealloc</code> <code class="type">bigint</code>
</p>
<p>
Total number of times <code class="structname">pg_stat_statements</code>
entries about the least-executed statements were deallocated
because more distinct statements than
<code class="varname">pg_stat_statements.max</code> were observed
</p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
<code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>
</p>
<p>
Time at which all statistics in the
<code class="structname">pg_stat_statements</code> view were last reset.
</p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="id-1.11.7.41.8"><div class="titlepage"><div><div><h3 class="title">F.32.3. Functions</h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt><span class="term">
<code class="function">pg_stat_statements_reset(userid Oid, dbid Oid, queryid bigint) returns void</code>
<a id="id-1.11.7.41.8.2.1.1.2" class="indexterm"></a>
</span></dt><dd><p>
<code class="function">pg_stat_statements_reset</code> discards statistics
gathered so far by <code class="filename">pg_stat_statements</code> corresponding
to the specified <code class="structfield">userid</code>, <code class="structfield">dbid</code>
and <code class="structfield">queryid</code>. If any of the parameters are not
specified, the default value <code class="literal">0</code>(invalid) is used for
each of them and the statistics that match with other parameters will be
reset. If no parameter is specified or all the specified parameters are
<code class="literal">0</code>(invalid), it will discard all statistics.
If all statistics in the <code class="filename">pg_stat_statements</code>
view are discarded, it will also reset the statistics in the
<code class="structname">pg_stat_statements_info</code> view.
By default, this function can only be executed by superusers.
Access may be granted to others using <code class="command">GRANT</code>.
</p></dd><dt><span class="term">
<code class="function">pg_stat_statements(showtext boolean) returns setof record</code>
<a id="id-1.11.7.41.8.2.2.1.2" class="indexterm"></a>
</span></dt><dd><p>
The <code class="structname">pg_stat_statements</code> view is defined in
terms of a function also named <code class="function">pg_stat_statements</code>.
It is possible for clients to call
the <code class="function">pg_stat_statements</code> function directly, and by
specifying <code class="literal">showtext := false</code> have query text be
omitted (that is, the <code class="literal">OUT</code> argument that corresponds
to the view's <code class="structfield">query</code> column will return nulls). This
feature is intended to support external tools that might wish to avoid
the overhead of repeatedly retrieving query texts of indeterminate
length. Such tools can instead cache the first query text observed
for each entry themselves, since that is
all <code class="filename">pg_stat_statements</code> itself does, and then retrieve
query texts only as needed. Since the server stores query texts in a
file, this approach may reduce physical I/O for repeated examination
of the <code class="structname">pg_stat_statements</code> data.
</p></dd></dl></div></div><div class="sect2" id="id-1.11.7.41.9"><div class="titlepage"><div><div><h3 class="title">F.32.4. Configuration Parameters</h3></div></div></div><div class="variablelist"><dl class="variablelist"><dt><span class="term">
<code class="varname">pg_stat_statements.max</code> (<code class="type">integer</code>)
<a id="id-1.11.7.41.9.2.1.1.3" class="indexterm"></a>
</span></dt><dd><p>
<code class="varname">pg_stat_statements.max</code> is the maximum number of
statements tracked by the module (i.e., the maximum number of rows
in the <code class="structname">pg_stat_statements</code> view). If more distinct
statements than that are observed, information about the least-executed
statements is discarded. The number of times such information was
discarded can be seen in the
<code class="structname">pg_stat_statements_info</code> view.
The default value is 5000.
This parameter can only be set at server start.
</p></dd><dt><span class="term">
<code class="varname">pg_stat_statements.track</code> (<code class="type">enum</code>)
<a id="id-1.11.7.41.9.2.2.1.3" class="indexterm"></a>
</span></dt><dd><p>
<code class="varname">pg_stat_statements.track</code> controls which statements
are counted by the module.
Specify <code class="literal">top</code> to track top-level statements (those issued
directly by clients), <code class="literal">all</code> to also track nested statements
(such as statements invoked within functions), or <code class="literal">none</code> to
disable statement statistics collection.
The default value is <code class="literal">top</code>.
Only superusers can change this setting.
</p></dd><dt><span class="term">
<code class="varname">pg_stat_statements.track_utility</code> (<code class="type">boolean</code>)
<a id="id-1.11.7.41.9.2.3.1.3" class="indexterm"></a>
</span></dt><dd><p>
<code class="varname">pg_stat_statements.track_utility</code> controls whether
utility commands are tracked by the module. Utility commands are
all those other than <code class="command">SELECT</code>, <code class="command">INSERT</code>,
<code class="command">UPDATE</code>, <code class="command">DELETE</code>, and <code class="command">MERGE</code>.
The default value is <code class="literal">on</code>.
Only superusers can change this setting.
</p></dd><dt><span class="term">
<code class="varname">pg_stat_statements.track_planning</code> (<code class="type">boolean</code>)
<a id="id-1.11.7.41.9.2.4.1.3" class="indexterm"></a>
</span></dt><dd><p>
<code class="varname">pg_stat_statements.track_planning</code> controls whether
planning operations and duration are tracked by the module.
Enabling this parameter may incur a noticeable performance penalty,
especially when statements with identical query structure are executed
by many concurrent connections which compete to update a small number of
<code class="structname">pg_stat_statements</code> entries.
The default value is <code class="literal">off</code>.
Only superusers can change this setting.
</p></dd><dt><span class="term">
<code class="varname">pg_stat_statements.save</code> (<code class="type">boolean</code>)
<a id="id-1.11.7.41.9.2.5.1.3" class="indexterm"></a>
</span></dt><dd><p>
<code class="varname">pg_stat_statements.save</code> specifies whether to
save statement statistics across server shutdowns.
If it is <code class="literal">off</code> then statistics are not saved at
shutdown nor reloaded at server start.
The default value is <code class="literal">on</code>.
This parameter can only be set in the <code class="filename">postgresql.conf</code>
file or on the server command line.
</p></dd></dl></div><p>
The module requires additional shared memory proportional to
<code class="varname">pg_stat_statements.max</code>. Note that this
memory is consumed whenever the module is loaded, even if
<code class="varname">pg_stat_statements.track</code> is set to <code class="literal">none</code>.
</p><p>
These parameters must be set in <code class="filename">postgresql.conf</code>.
Typical usage might be:
</p><pre class="programlisting">
# postgresql.conf
shared_preload_libraries = 'pg_stat_statements'
compute_query_id = on
pg_stat_statements.max = 10000
pg_stat_statements.track = all
</pre><p>
</p></div><div class="sect2" id="id-1.11.7.41.10"><div class="titlepage"><div><div><h3 class="title">F.32.5. Sample Output</h3></div></div></div><pre class="screen">
bench=# SELECT pg_stat_statements_reset();
$ pgbench -i bench
$ pgbench -c10 -t300 bench
bench=# \x
bench=# SELECT query, calls, total_exec_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_exec_time DESC LIMIT 5;
-[ RECORD 1 ]---+--------------------------------------------------------------------
query | UPDATE pgbench_branches SET bbalance = bbalance + $1 WHERE bid = $2
calls | 3000
total_exec_time | 25565.855387
rows | 3000
hit_percent | 100.0000000000000000
-[ RECORD 2 ]---+--------------------------------------------------------------------
query | UPDATE pgbench_tellers SET tbalance = tbalance + $1 WHERE tid = $2
calls | 3000
total_exec_time | 20756.669379
rows | 3000
hit_percent | 100.0000000000000000
-[ RECORD 3 ]---+--------------------------------------------------------------------
query | copy pgbench_accounts from stdin
calls | 1
total_exec_time | 291.865911
rows | 100000
hit_percent | 100.0000000000000000
-[ RECORD 4 ]---+--------------------------------------------------------------------
query | UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2
calls | 3000
total_exec_time | 271.232977
rows | 3000
hit_percent | 98.8454011741682975
-[ RECORD 5 ]---+--------------------------------------------------------------------
query | alter table pgbench_accounts add primary key (aid)
calls | 1
total_exec_time | 160.588563
rows | 0
hit_percent | 100.0000000000000000
bench=# SELECT pg_stat_statements_reset(0,0,s.queryid) FROM pg_stat_statements AS s
WHERE s.query = 'UPDATE pgbench_branches SET bbalance = bbalance + $1 WHERE bid = $2';
bench=# SELECT query, calls, total_exec_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_exec_time DESC LIMIT 5;
-[ RECORD 1 ]---+--------------------------------------------------------------------
query | UPDATE pgbench_tellers SET tbalance = tbalance + $1 WHERE tid = $2
calls | 3000
total_exec_time | 20756.669379
rows | 3000
hit_percent | 100.0000000000000000
-[ RECORD 2 ]---+--------------------------------------------------------------------
query | copy pgbench_accounts from stdin
calls | 1
total_exec_time | 291.865911
rows | 100000
hit_percent | 100.0000000000000000
-[ RECORD 3 ]---+--------------------------------------------------------------------
query | UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2
calls | 3000
total_exec_time | 271.232977
rows | 3000
hit_percent | 98.8454011741682975
-[ RECORD 4 ]---+--------------------------------------------------------------------
query | alter table pgbench_accounts add primary key (aid)
calls | 1
total_exec_time | 160.588563
rows | 0
hit_percent | 100.0000000000000000
-[ RECORD 5 ]---+--------------------------------------------------------------------
query | vacuum analyze pgbench_accounts
calls | 1
total_exec_time | 136.448116
rows | 0
hit_percent | 99.9201915403032721
bench=# SELECT pg_stat_statements_reset(0,0,0);
bench=# SELECT query, calls, total_exec_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_exec_time DESC LIMIT 5;
-[ RECORD 1 ]---+-----------------------------------------------------------------------------
query | SELECT pg_stat_statements_reset(0,0,0)
calls | 1
total_exec_time | 0.189497
rows | 1
hit_percent |
-[ RECORD 2 ]---+-----------------------------------------------------------------------------
query | SELECT query, calls, total_exec_time, rows, $1 * shared_blks_hit / +
| nullif(shared_blks_hit + shared_blks_read, $2) AS hit_percent+
| FROM pg_stat_statements ORDER BY total_exec_time DESC LIMIT $3
calls | 0
total_exec_time | 0
rows | 0
hit_percent |
</pre></div><div class="sect2" id="id-1.11.7.41.11"><div class="titlepage"><div><div><h3 class="title">F.32.6. Authors</h3></div></div></div><p>
Takahiro Itagaki <code class="email"><<a class="email" href="mailto:itagaki.takahiro@oss.ntt.co.jp">itagaki.takahiro@oss.ntt.co.jp</a>></code>.
Query normalization added by Peter Geoghegan <code class="email"><<a class="email" href="mailto:peter@2ndquadrant.com">peter@2ndquadrant.com</a>></code>.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="pgrowlocks.html" title="F.31. pgrowlocks">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="pgstattuple.html" title="F.33. pgstattuple">Next</a></td></tr><tr><td width="40%" align="left" valign="top">F.31. pgrowlocks </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.7 Documentation">Home</a></td><td width="40%" align="right" valign="top"> F.33. pgstattuple</td></tr></table></div></body></html>
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