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<sect1 id="pgstatstatements" xreflabel="pg_stat_statements">
<title>pg_stat_statements</title>
<indexterm zone="pgstatstatements">
<primary>pg_stat_statements</primary>
</indexterm>
<para>
The <filename>pg_stat_statements</filename> module provides a means for
tracking planning and execution statistics of all SQL statements executed by
a server.
</para>
<para>
The module must be loaded by adding <literal>pg_stat_statements</literal> to
<xref linkend="guc-shared-preload-libraries"/> in
<filename>postgresql.conf</filename>, 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 <xref linkend="guc-compute-query-id"/>
is set to <literal>auto</literal> or <literal>on</literal>, or any third-party
module that calculates query identifiers is loaded.
</para>
<para>
When <filename>pg_stat_statements</filename> is active, it tracks
statistics across all databases of the server. To access and manipulate
these statistics, the module provides views
<structname>pg_stat_statements</structname> and
<structname>pg_stat_statements_info</structname>,
and the utility functions <function>pg_stat_statements_reset</function> and
<function>pg_stat_statements</function>. These are not available globally but
can be enabled for a specific database with
<command>CREATE EXTENSION pg_stat_statements</command>.
</para>
<sect2>
<title>The <structname>pg_stat_statements</structname> View</title>
<para>
The statistics gathered by the module are made available via a
view named <structname>pg_stat_statements</structname>. 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
<xref linkend="pgstatstatements-columns"/>.
</para>
<table id="pgstatstatements-columns">
<title><structname>pg_stat_statements</structname> Columns</title>
<tgroup cols="1">
<thead>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
Column Type
</para>
<para>
Description
</para></entry>
</row>
</thead>
<tbody>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>userid</structfield> <type>oid</type>
(references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
</para>
<para>
OID of user who executed the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>dbid</structfield> <type>oid</type>
(references <link linkend="catalog-pg-database"><structname>pg_database</structname></link>.<structfield>oid</structfield>)
</para>
<para>
OID of database in which the statement was executed
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>toplevel</structfield> <type>bool</type>
</para>
<para>
True if the query was executed as a top-level statement
(always true if <varname>pg_stat_statements.track</varname> is set to
<literal>top</literal>)
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>queryid</structfield> <type>bigint</type>
</para>
<para>
Hash code to identify identical normalized queries.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>query</structfield> <type>text</type>
</para>
<para>
Text of a representative statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>plans</structfield> <type>bigint</type>
</para>
<para>
Number of times the statement was planned
(if <varname>pg_stat_statements.track_planning</varname> is enabled,
otherwise zero)
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>total_plan_time</structfield> <type>double precision</type>
</para>
<para>
Total time spent planning the statement, in milliseconds
(if <varname>pg_stat_statements.track_planning</varname> is enabled,
otherwise zero)
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>min_plan_time</structfield> <type>double precision</type>
</para>
<para>
Minimum time spent planning the statement, in milliseconds
(if <varname>pg_stat_statements.track_planning</varname> is enabled,
otherwise zero)
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>max_plan_time</structfield> <type>double precision</type>
</para>
<para>
Maximum time spent planning the statement, in milliseconds
(if <varname>pg_stat_statements.track_planning</varname> is enabled,
otherwise zero)
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>mean_plan_time</structfield> <type>double precision</type>
</para>
<para>
Mean time spent planning the statement, in milliseconds
(if <varname>pg_stat_statements.track_planning</varname> is enabled,
otherwise zero)
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>stddev_plan_time</structfield> <type>double precision</type>
</para>
<para>
Population standard deviation of time spent planning the statement,
in milliseconds
(if <varname>pg_stat_statements.track_planning</varname> is enabled,
otherwise zero)
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>calls</structfield> <type>bigint</type>
</para>
<para>
Number of times the statement was executed
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>total_exec_time</structfield> <type>double precision</type>
</para>
<para>
Total time spent executing the statement, in milliseconds
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>min_exec_time</structfield> <type>double precision</type>
</para>
<para>
Minimum time spent executing the statement, in milliseconds
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>max_exec_time</structfield> <type>double precision</type>
</para>
<para>
Maximum time spent executing the statement, in milliseconds
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>mean_exec_time</structfield> <type>double precision</type>
</para>
<para>
Mean time spent executing the statement, in milliseconds
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>stddev_exec_time</structfield> <type>double precision</type>
</para>
<para>
Population standard deviation of time spent executing the statement, in milliseconds
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>rows</structfield> <type>bigint</type>
</para>
<para>
Total number of rows retrieved or affected by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>shared_blks_hit</structfield> <type>bigint</type>
</para>
<para>
Total number of shared block cache hits by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>shared_blks_read</structfield> <type>bigint</type>
</para>
<para>
Total number of shared blocks read by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>shared_blks_dirtied</structfield> <type>bigint</type>
</para>
<para>
Total number of shared blocks dirtied by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>shared_blks_written</structfield> <type>bigint</type>
</para>
<para>
Total number of shared blocks written by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>local_blks_hit</structfield> <type>bigint</type>
</para>
<para>
Total number of local block cache hits by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>local_blks_read</structfield> <type>bigint</type>
</para>
<para>
Total number of local blocks read by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>local_blks_dirtied</structfield> <type>bigint</type>
</para>
<para>
Total number of local blocks dirtied by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>local_blks_written</structfield> <type>bigint</type>
</para>
<para>
Total number of local blocks written by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>temp_blks_read</structfield> <type>bigint</type>
</para>
<para>
Total number of temp blocks read by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>temp_blks_written</structfield> <type>bigint</type>
</para>
<para>
Total number of temp blocks written by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>blk_read_time</structfield> <type>double precision</type>
</para>
<para>
Total time the statement spent reading blocks, in milliseconds
(if <xref linkend="guc-track-io-timing"/> is enabled, otherwise zero)
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>blk_write_time</structfield> <type>double precision</type>
</para>
<para>
Total time the statement spent writing blocks, in milliseconds
(if <xref linkend="guc-track-io-timing"/> is enabled, otherwise zero)
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>wal_records</structfield> <type>bigint</type>
</para>
<para>
Total number of WAL records generated by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>wal_fpi</structfield> <type>bigint</type>
</para>
<para>
Total number of WAL full page images generated by the statement
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>wal_bytes</structfield> <type>numeric</type>
</para>
<para>
Total amount of WAL generated by the statement in bytes
</para></entry>
</row>
</tbody>
</tgroup>
</table>
<para>
For security reasons, only superusers and members of the
<literal>pg_read_all_stats</literal> role are allowed to see the SQL text and
<structfield>queryid</structfield> of queries executed by other users.
Other users can see the statistics, however, if the view has been installed
in their database.
</para>
<para>
Plannable queries (that is, <command>SELECT</command>, <command>INSERT</command>,
<command>UPDATE</command>, and <command>DELETE</command>) are combined into a single
<structname>pg_stat_statements</structname> 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.
</para>
<note>
<para>
The following details about constant replacement and
<structfield>queryid</structfield> only apply when <xref
linkend="guc-compute-query-id"/> is enabled. If you use an external
module instead to compute <structfield>queryid</structfield>, you
should refer to its documentation for details.
</para>
</note>
<para>
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 <literal>$1</literal>, in the <structname>pg_stat_statements</structname>
display.
The rest of the query text is that of the first query that had the
particular <structfield>queryid</structfield> hash value associated with the
<structname>pg_stat_statements</structname> entry.
</para>
<para>
In some cases, queries with visibly different texts might get merged into a
single <structname>pg_stat_statements</structname> 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.)
</para>
<para>
Since the <structfield>queryid</structfield> 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 <varname>search_path</varname> settings.
</para>
<para>
Consumers of <structname>pg_stat_statements</structname> may wish to use
<structfield>queryid</structfield> (perhaps in combination with
<structfield>dbid</structfield> and <structfield>userid</structfield>) 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 <structfield>queryid</structfield> 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,
<filename>pg_stat_statements</filename> 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 <structfield>queryid</structfield>
will be stable across major versions of <productname>PostgreSQL</productname>.
</para>
<para>
As a rule of thumb, <structfield>queryid</structfield> values can be assumed to be
stable and comparable only so long as the underlying server version and
catalog metadata details stay exactly the same. Two servers
participating in replication based on physical WAL replay can be expected
to have identical <structfield>queryid</structfield> values for the same query.
However, logical replication schemes do not promise to keep replicas
identical in all relevant details, so <structfield>queryid</structfield> will
not be a useful identifier for accumulating costs across a set of logical
replicas. If in doubt, direct testing is recommended.
</para>
<para>
The parameter symbols used to replace constants in
representative query texts start from the next number after the
highest <literal>$</literal><replaceable>n</replaceable> parameter in the original query
text, or <literal>$1</literal> if there was none. It's worth noting that in
some cases there may be hidden parameter symbols that affect this
numbering. For example, <application>PL/pgSQL</application> uses hidden parameter
symbols to insert values of function local variables into queries, so that
a <application>PL/pgSQL</application> statement like <literal>SELECT i + 1 INTO j</literal>
would have representative text like <literal>SELECT i + $2</literal>.
</para>
<para>
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, <filename>pg_stat_statements</filename> may
choose to discard the query texts, whereupon all existing entries in
the <structname>pg_stat_statements</structname> view will show
null <structfield>query</structfield> fields, though the statistics associated with
each <structfield>queryid</structfield> are preserved. If this happens, consider
reducing <varname>pg_stat_statements.max</varname> to prevent
recurrences.
</para>
<para>
<structfield>plans</structfield> and <structfield>calls</structfield> 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.
</para>
</sect2>
<sect2>
<title>The <structname>pg_stat_statements_info</structname> View</title>
<indexterm>
<primary>pg_stat_statements_info</primary>
</indexterm>
<para>
The statistics of the <filename>pg_stat_statements</filename> module
itself are tracked and made available via a view named
<structname>pg_stat_statements_info</structname>. This view contains
only a single row. The columns of the view are shown in
<xref linkend="pgstatstatementsinfo-columns"/>.
</para>
<table id="pgstatstatementsinfo-columns">
<title><structname>pg_stat_statements_info</structname> Columns</title>
<tgroup cols="1">
<thead>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
Column Type
</para>
<para>
Description
</para></entry>
</row>
</thead>
<tbody>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>dealloc</structfield> <type>bigint</type>
</para>
<para>
Total number of times <structname>pg_stat_statements</structname>
entries about the least-executed statements were deallocated
because more distinct statements than
<varname>pg_stat_statements.max</varname> were observed
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>stats_reset</structfield> <type>timestamp with time zone</type>
</para>
<para>
Time at which all statistics in the
<structname>pg_stat_statements</structname> view were last reset.
</para></entry>
</row>
</tbody>
</tgroup>
</table>
</sect2>
<sect2>
<title>Functions</title>
<variablelist>
<varlistentry>
<term>
<function>pg_stat_statements_reset(userid Oid, dbid Oid, queryid bigint) returns void</function>
<indexterm>
<primary>pg_stat_statements_reset</primary>
</indexterm>
</term>
<listitem>
<para>
<function>pg_stat_statements_reset</function> discards statistics
gathered so far by <filename>pg_stat_statements</filename> corresponding
to the specified <structfield>userid</structfield>, <structfield>dbid</structfield>
and <structfield>queryid</structfield>. If any of the parameters are not
specified, the default value <literal>0</literal>(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
<literal>0</literal>(invalid), it will discard all statistics.
If all statistics in the <filename>pg_stat_statements</filename>
view are discarded, it will also reset the statistics in the
<structname>pg_stat_statements_info</structname> view.
By default, this function can only be executed by superusers.
Access may be granted to others using <command>GRANT</command>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<function>pg_stat_statements(showtext boolean) returns setof record</function>
<indexterm>
<primary>pg_stat_statements</primary>
<secondary>function</secondary>
</indexterm>
</term>
<listitem>
<para>
The <structname>pg_stat_statements</structname> view is defined in
terms of a function also named <function>pg_stat_statements</function>.
It is possible for clients to call
the <function>pg_stat_statements</function> function directly, and by
specifying <literal>showtext := false</literal> have query text be
omitted (that is, the <literal>OUT</literal> argument that corresponds
to the view's <structfield>query</structfield> 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 <filename>pg_stat_statements</filename> 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 <structname>pg_stat_statements</structname> data.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>
<sect2>
<title>Configuration Parameters</title>
<variablelist>
<varlistentry>
<term>
<varname>pg_stat_statements.max</varname> (<type>integer</type>)
</term>
<listitem>
<para>
<varname>pg_stat_statements.max</varname> is the maximum number of
statements tracked by the module (i.e., the maximum number of rows
in the <structname>pg_stat_statements</structname> 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
<structname>pg_stat_statements_info</structname> view.
The default value is 5000.
This parameter can only be set at server start.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>pg_stat_statements.track</varname> (<type>enum</type>)
</term>
<listitem>
<para>
<varname>pg_stat_statements.track</varname> controls which statements
are counted by the module.
Specify <literal>top</literal> to track top-level statements (those issued
directly by clients), <literal>all</literal> to also track nested statements
(such as statements invoked within functions), or <literal>none</literal> to
disable statement statistics collection.
The default value is <literal>top</literal>.
Only superusers can change this setting.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>pg_stat_statements.track_utility</varname> (<type>boolean</type>)
</term>
<listitem>
<para>
<varname>pg_stat_statements.track_utility</varname> controls whether
utility commands are tracked by the module. Utility commands are
all those other than <command>SELECT</command>, <command>INSERT</command>,
<command>UPDATE</command> and <command>DELETE</command>.
The default value is <literal>on</literal>.
Only superusers can change this setting.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>pg_stat_statements.track_planning</varname> (<type>boolean</type>)
</term>
<listitem>
<para>
<varname>pg_stat_statements.track_planning</varname> 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
<structname>pg_stat_statements</structname> entries.
The default value is <literal>off</literal>.
Only superusers can change this setting.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>pg_stat_statements.save</varname> (<type>boolean</type>)
</term>
<listitem>
<para>
<varname>pg_stat_statements.save</varname> specifies whether to
save statement statistics across server shutdowns.
If it is <literal>off</literal> then statistics are not saved at
shutdown nor reloaded at server start.
The default value is <literal>on</literal>.
This parameter can only be set in the <filename>postgresql.conf</filename>
file or on the server command line.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
The module requires additional shared memory proportional to
<varname>pg_stat_statements.max</varname>. Note that this
memory is consumed whenever the module is loaded, even if
<varname>pg_stat_statements.track</varname> is set to <literal>none</literal>.
</para>
<para>
These parameters must be set in <filename>postgresql.conf</filename>.
Typical usage might be:
<programlisting>
# postgresql.conf
shared_preload_libraries = 'pg_stat_statements'
compute_query_id = on
pg_stat_statements.max = 10000
pg_stat_statements.track = all
</programlisting>
</para>
</sect2>
<sect2>
<title>Sample Output</title>
<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 ]---+--------------------------------------------------&zwsp;------------------
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 ]---+--------------------------------------------------&zwsp;------------------
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 ]---+--------------------------------------------------&zwsp;------------------
query | copy pgbench_accounts from stdin
calls | 1
total_exec_time | 291.865911
rows | 100000
hit_percent | 100.0000000000000000
-[ RECORD 4 ]---+--------------------------------------------------&zwsp;------------------
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 ]---+--------------------------------------------------&zwsp;------------------
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 ]---+--------------------------------------------------&zwsp;------------------
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 ]---+--------------------------------------------------&zwsp;------------------
query | copy pgbench_accounts from stdin
calls | 1
total_exec_time | 291.865911
rows | 100000
hit_percent | 100.0000000000000000
-[ RECORD 3 ]---+--------------------------------------------------&zwsp;------------------
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 ]---+--------------------------------------------------&zwsp;------------------
query | alter table pgbench_accounts add primary key (aid)
calls | 1
total_exec_time | 160.588563
rows | 0
hit_percent | 100.0000000000000000
-[ RECORD 5 ]---+--------------------------------------------------&zwsp;------------------
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 ]---+--------------------------------------------------&zwsp;---------------------------
query | SELECT pg_stat_statements_reset(0,0,0)
calls | 1
total_exec_time | 0.189497
rows | 1
hit_percent |
-[ RECORD 2 ]---+--------------------------------------------------&zwsp;---------------------------
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 |
</screen>
</sect2>
<sect2>
<title>Authors</title>
<para>
Takahiro Itagaki <email>itagaki.takahiro@oss.ntt.co.jp</email>.
Query normalization added by Peter Geoghegan <email>peter@2ndquadrant.com</email>.
</para>
</sect2>
</sect1>