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<!-- $PostgreSQL: pgsql/doc/src/sgml/pgbench.sgml,v 1.13 2010/03/23 01:29:22 itagaki Exp $ --> <!-- $PostgreSQL: pgsql/doc/src/sgml/pgbench.sgml,v 1.14 2010/03/23 04:09:17 itagaki Exp $ -->
<sect1 id="pgbench"> <sect1 id="pgbench">
<title>pgbench</title> <title>pgbench</title>
<indexterm zone="pgbench"> <indexterm zone="pgbench">
<primary>pgbench</primary> <primary>pgbench</primary>
</indexterm> </indexterm>
<para> <para>
<application>pgbench</application> is a simple program for running benchmark <application>pgbench</application> is a simple program for running benchmark
tests on <productname>PostgreSQL</>. It runs the same sequence of SQL tests on <productname>PostgreSQL</>. It runs the same sequence of SQL
commands over and over, possibly in multiple concurrent database sessions, commands over and over, possibly in multiple concurrent database sessions,
and then calculates the average transaction rate (transactions per second). and then calculates the average transaction rate (transactions per second).
By default, <application>pgbench</application> tests a scenario that is By default, <application>pgbench</application> tests a scenario that is
loosely based on TPC-B, involving five <command>SELECT</>, loosely based on TPC-B, involving five <command>SELECT</>,
<command>UPDATE</>, and <command>INSERT</> commands per transaction. <command>UPDATE</>, and <command>INSERT</> commands per transaction.
However, it is easy to test other cases by writing your own transaction However, it is easy to test other cases by writing your own transaction
script files. script files.
</para> </para>
<para> <para>
Typical output from pgbench looks like: Typical output from pgbench looks like:
<programlisting> <programlisting>
transaction type: TPC-B (sort of) transaction type: TPC-B (sort of)
scaling factor: 10 scaling factor: 10
query mode: simple query mode: simple
number of clients: 10 number of clients: 10
number of threads: 1 number of threads: 1
number of transactions per client: 1000 number of transactions per client: 1000
number of transactions actually processed: 10000/10000 number of transactions actually processed: 10000/10000
tps = 85.184871 (including connections establishing) tps = 85.184871 (including connections establishing)
tps = 85.296346 (excluding connections establishing) tps = 85.296346 (excluding connections establishing)
</programlisting> </programlisting>
The first six lines report some of the most important parameter The first six lines report some of the most important parameter
settings. The next line reports the number of transactions completed settings. The next line reports the number of transactions completed
and intended (the latter being just the product of number of clients and intended (the latter being just the product of number of clients
and number of transactions per client); these will be equal unless the run and number of transactions per client); these will be equal unless the run
failed before completion. The last two lines report the TPS rate, failed before completion. The last two lines report the TPS rate,
figured with and without counting the time to start database sessions. figured with and without counting the time to start database sessions.
</para> </para>
<sect2> <sect2>
<title>Overview</title> <title>Overview</title>
<para> <para>
The default TPC-B-like transaction test requires specific tables to be The default TPC-B-like transaction test requires specific tables to be
set up beforehand. <application>pgbench</> should be invoked with set up beforehand. <application>pgbench</> should be invoked with
the <literal>-i</> (initialize) option to create and populate these the <literal>-i</> (initialize) option to create and populate these
tables. (When you are testing a custom script, you don't need this tables. (When you are testing a custom script, you don't need this
step, but will instead need to do whatever setup your test needs.) step, but will instead need to do whatever setup your test needs.)
Initialization looks like: Initialization looks like:
<programlisting> <programlisting>
pgbench -i <optional> <replaceable>other-options</> </optional> <replaceable>dbname</> pgbench -i <optional> <replaceable>other-options</> </optional> <replaceable>dbname</>
</programlisting> </programlisting>
where <replaceable>dbname</> is the name of the already-created where <replaceable>dbname</> is the name of the already-created
database to test in. (You may also need <literal>-h</>, database to test in. (You may also need <literal>-h</>,
<literal>-p</>, and/or <literal>-U</> options to specify how to <literal>-p</>, and/or <literal>-U</> options to specify how to
connect to the database server.) connect to the database server.)
</para> </para>
<caution> <caution>
<para> <para>
<literal>pgbench -i</> creates four tables <structname>pgbench_accounts</>, <literal>pgbench -i</> creates four tables <structname>pgbench_accounts</>,
<structname>pgbench_branches</>, <structname>pgbench_history</>, and <structname>pgbench_branches</>, <structname>pgbench_history</>, and
<structname>pgbench_tellers</>, <structname>pgbench_tellers</>,
destroying any existing tables of these names. destroying any existing tables of these names.
Be very careful to use another database if you have tables having these Be very careful to use another database if you have tables having these
names! names!
</para> </para>
</caution> </caution>
<para> <para>
At the default <quote>scale factor</> of 1, the tables initially At the default <quote>scale factor</> of 1, the tables initially
contain this many rows: contain this many rows:
</para> </para>
<programlisting> <programlisting>
table # of rows table # of rows
--------------------------------- ---------------------------------
pgbench_branches 1 pgbench_branches 1
pgbench_tellers 10 pgbench_tellers 10
pgbench_accounts 100000 pgbench_accounts 100000
pgbench_history 0 pgbench_history 0
</programlisting> </programlisting>
<para> <para>
You can (and, for most purposes, probably should) increase the number You can (and, for most purposes, probably should) increase the number
of rows by using the <literal>-s</> (scale factor) option. The of rows by using the <literal>-s</> (scale factor) option. The
<literal>-F</> (fillfactor) option might also be used at this point. <literal>-F</> (fillfactor) option might also be used at this point.
</para> </para>
<para> <para>
Once you have done the necessary setup, you can run your benchmark Once you have done the necessary setup, you can run your benchmark
with a command that doesn't include <literal>-i</>, that is with a command that doesn't include <literal>-i</>, that is
<programlisting> <programlisting>
pgbench <optional> <replaceable>options</> </optional> <replaceable>dbname</> pgbench <optional> <replaceable>options</> </optional> <replaceable>dbname</>
</programlisting> </programlisting>
In nearly all cases, you'll need some options to make a useful test. In nearly all cases, you'll need some options to make a useful test.
The most important options are <literal>-c</> (number of clients), The most important options are <literal>-c</> (number of clients),
<literal>-t</> (number of transactions), <literal>-T</> (time limit), <literal>-t</> (number of transactions), <literal>-T</> (time limit),
and <literal>-f</> (specify a custom script file). and <literal>-f</> (specify a custom script file).
See below for a full list. See below for a full list.
</para> </para>
<para> <para>
<xref linkend="pgbench-init-options"> shows options that are used <xref linkend="pgbench-init-options"> shows options that are used
during database initialization, while during database initialization, while
<xref linkend="pgbench-run-options"> shows options that are used <xref linkend="pgbench-run-options"> shows options that are used
while running benchmarks, and while running benchmarks, and
<xref linkend="pgbench-common-options"> shows options that are useful <xref linkend="pgbench-common-options"> shows options that are useful
in both cases. in both cases.
</para> </para>
<table id="pgbench-init-options"> <table id="pgbench-init-options">
<title><application>pgbench</application> initialization options</title> <title><application>pgbench</application> initialization options</title>
<tgroup cols="2"> <tgroup cols="2">
<thead> <thead>
<row> <row>
<entry>Option</entry> <entry>Option</entry>
<entry>Description</entry> <entry>Description</entry>
</row> </row>
</thead> </thead>
<tbody> <tbody>
<row> <row>
<entry><literal>-i</literal></entry> <entry><literal>-i</literal></entry>
<entry> <entry>
Required to invoke initialization mode. Required to invoke initialization mode.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-s</literal> <replaceable>scale_factor</></entry> <entry><literal>-s</literal> <replaceable>scale_factor</></entry>
<entry> <entry>
Multiply the number of rows generated by the scale factor. Multiply the number of rows generated by the scale factor.
For example, <literal>-s 100</> will create 10,000,000 rows For example, <literal>-s 100</> will create 10,000,000 rows
in the <structname>pgbench_accounts</> table. Default is 1. in the <structname>pgbench_accounts</> table. Default is 1.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-F</literal> <replaceable>fillfactor</></entry> <entry><literal>-F</literal> <replaceable>fillfactor</></entry>
<entry> <entry>
Create the <structname>pgbench_accounts</>, Create the <structname>pgbench_accounts</>,
<structname>pgbench_tellers</> and <structname>pgbench_tellers</> and
<structname>pgbench_branches</> tables with the given fillfactor. <structname>pgbench_branches</> tables with the given fillfactor.
Default is 100. Default is 100.
</entry> </entry>
</row> </row>
</tbody> </tbody>
</tgroup> </tgroup>
</table> </table>
<table id="pgbench-run-options"> <table id="pgbench-run-options">
<title><application>pgbench</application> benchmarking options</title> <title><application>pgbench</application> benchmarking options</title>
<tgroup cols="2"> <tgroup cols="2">
<thead> <thead>
<row> <row>
<entry>Option</entry> <entry>Option</entry>
<entry>Description</entry> <entry>Description</entry>
</row> </row>
</thead> </thead>
<tbody> <tbody>
<row> <row>
<entry><literal>-c</literal> <replaceable>clients</></entry> <entry><literal>-c</literal> <replaceable>clients</></entry>
<entry> <entry>
Number of clients simulated, that is, number of concurrent database Number of clients simulated, that is, number of concurrent database
sessions. Default is 1. sessions. Default is 1.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-j</literal> <replaceable>threads</></entry> <entry><literal>-j</literal> <replaceable>threads</></entry>
<entry> <entry>
Number of worker threads within <application>pgbench</application>. Number of worker threads within <application>pgbench</application>.
Using more than one thread can be helpful on multi-CPU machines. Using more than one thread can be helpful on multi-CPU machines.
The number of clients must be a multiple of the number of threads, The number of clients must be a multiple of the number of threads,
since each thread is given the same number of client sessions to manage. since each thread is given the same number of client sessions to manage.
Default is 1. Default is 1.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-t</literal> <replaceable>transactions</></entry> <entry><literal>-t</literal> <replaceable>transactions</></entry>
<entry> <entry>
Number of transactions each client runs. Default is 10. Number of transactions each client runs. Default is 10.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-T</literal> <replaceable>seconds</></entry> <entry><literal>-T</literal> <replaceable>seconds</></entry>
<entry> <entry>
Run the test for this many seconds, rather than a fixed number of Run the test for this many seconds, rather than a fixed number of
transactions per client. <literal>-t</literal> and transactions per client. <literal>-t</literal> and
<literal>-T</literal> are mutually exclusive. <literal>-T</literal> are mutually exclusive.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-M</literal> <replaceable>querymode</></entry> <entry><literal>-M</literal> <replaceable>querymode</></entry>
<entry> <entry>
Protocol to use for submitting queries to the server: Protocol to use for submitting queries to the server:
<itemizedlist> <itemizedlist>
<listitem> <listitem>
<para><literal>simple</>: use simple query protocol.</para> <para><literal>simple</>: use simple query protocol.</para>
</listitem> </listitem>
<listitem> <listitem>
<para><literal>extended</>: use extended query protocol.</para> <para><literal>extended</>: use extended query protocol.</para>
</listitem> </listitem>
<listitem> <listitem>
<para><literal>prepared</>: use extended query protocol with prepared statements.</para> <para><literal>prepared</>: use extended query protocol with prepared statements.</para>
</listitem> </listitem>
</itemizedlist> </itemizedlist>
The default is simple query protocol. (See <xref linkend="protocol"> The default is simple query protocol. (See <xref linkend="protocol">
for more information.) for more information.)
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-N</literal></entry> <entry><literal>-N</literal></entry>
<entry> <entry>
Do not update <structname>pgbench_tellers</> and Do not update <structname>pgbench_tellers</> and
<structname>pgbench_branches</>. <structname>pgbench_branches</>.
This will avoid update contention on these tables, but This will avoid update contention on these tables, but
it makes the test case even less like TPC-B. it makes the test case even less like TPC-B.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-S</literal></entry> <entry><literal>-S</literal></entry>
<entry> <entry>
Perform select-only transactions instead of TPC-B-like test. Perform select-only transactions instead of TPC-B-like test.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-f</literal> <replaceable>filename</></entry> <entry><literal>-f</literal> <replaceable>filename</></entry>
<entry> <entry>
Read transaction script from <replaceable>filename</>. Read transaction script from <replaceable>filename</>.
See below for details. See below for details.
<literal>-N</literal>, <literal>-S</literal>, and <literal>-f</literal> <literal>-N</literal>, <literal>-S</literal>, and <literal>-f</literal>
are mutually exclusive. are mutually exclusive.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-n</literal></entry> <entry><literal>-n</literal></entry>
<entry> <entry>
Perform no vacuuming before running the test. Perform no vacuuming before running the test.
This option is <emphasis>necessary</> This option is <emphasis>necessary</>
if you are running a custom test scenario that does not include if you are running a custom test scenario that does not include
the standard tables <structname>pgbench_accounts</>, the standard tables <structname>pgbench_accounts</>,
<structname>pgbench_branches</>, <structname>pgbench_history</>, and <structname>pgbench_branches</>, <structname>pgbench_history</>, and
<structname>pgbench_tellers</>. <structname>pgbench_tellers</>.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-v</literal></entry> <entry><literal>-v</literal></entry>
<entry> <entry>
Vacuum all four standard tables before running the test. Vacuum all four standard tables before running the test.
With neither <literal>-n</> nor <literal>-v</>, pgbench will vacuum the With neither <literal>-n</> nor <literal>-v</>, pgbench will vacuum the
<structname>pgbench_tellers</> and <structname>pgbench_branches</> <structname>pgbench_tellers</> and <structname>pgbench_branches</>
tables, and will truncate <structname>pgbench_history</>. tables, and will truncate <structname>pgbench_history</>.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-D</literal> <replaceable>varname</><literal>=</><replaceable>value</></entry> <entry><literal>-D</literal> <replaceable>varname</><literal>=</><replaceable>value</></entry>
<entry> <entry>
Define a variable for use by a custom script (see below). Define a variable for use by a custom script (see below).
Multiple <literal>-D</> options are allowed. Multiple <literal>-D</> options are allowed.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-C</literal></entry> <entry><literal>-C</literal></entry>
<entry> <entry>
Establish a new connection for each transaction, rather than Establish a new connection for each transaction, rather than
doing it just once per client session. doing it just once per client session.
This is useful to measure the connection overhead. This is useful to measure the connection overhead.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-l</literal></entry> <entry><literal>-l</literal></entry>
<entry> <entry>
Write the time taken by each transaction to a logfile. Write the time taken by each transaction to a logfile.
See below for details. See below for details.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-s</literal> <replaceable>scale_factor</></entry> <entry><literal>-s</literal> <replaceable>scale_factor</></entry>
<entry> <entry>
Report the specified scale factor in <application>pgbench</>'s Report the specified scale factor in <application>pgbench</>'s
output. With the built-in tests, this is not necessary; the output. With the built-in tests, this is not necessary; the
correct scale factor will be detected by counting the number of correct scale factor will be detected by counting the number of
rows in the <structname>pgbench_branches</> table. However, when testing rows in the <structname>pgbench_branches</> table. However, when testing
custom benchmarks (<literal>-f</> option), the scale factor custom benchmarks (<literal>-f</> option), the scale factor
will be reported as 1 unless this option is used. will be reported as 1 unless this option is used.
</entry> </entry>
</row> </row>
<row> <row>
<entry><literal>-d</literal></entry> <entry><literal>-d</literal></entry>
<entry> <entry>
Print debugging output. Print debugging output.
</entry> </entry>
</row> </row>
</tbody> </tbody>
</tgroup> </tgroup>
</table> </table>
<table id="pgbench-common-options"> <table id="pgbench-common-options">
<title><application>pgbench</application> common options</title> <title><application>pgbench</application> common options</title>
<tgroup cols="2"> <tgroup cols="2">
<thead> <thead>
<row> <row>
<entry>Option</entry> <entry>Option</entry>
<entry>Description</entry> <entry>Description</entry>
</row> </row>
</thead> </thead>
<tbody> <tbody>
<row> <row>
<entry><literal>-h</literal> <replaceable>hostname</></entry> <entry><literal>-h</literal> <replaceable>hostname</></entry>
<entry>database server's host</entry> <entry>database server's host</entry>
</row> </row>
<row> <row>
<entry><literal>-p</literal> <replaceable>port</></entry> <entry><literal>-p</literal> <replaceable>port</></entry>
<entry>database server's port</entry> <entry>database server's port</entry>
</row> </row>
<row> <row>
<entry><literal>-U</literal> <replaceable>login</></entry> <entry><literal>-U</literal> <replaceable>login</></entry>
<entry>username to connect as</entry> <entry>username to connect as</entry>
</row> </row>
</tbody> </tbody>
</tgroup> </tgroup>
</table> </table>
</sect2> </sect2>
<sect2> <sect2>
<title>What is the <quote>transaction</> actually performed in pgbench?</title> <title>What is the <quote>transaction</> actually performed in pgbench?</title>
<para> <para>
The default transaction script issues seven commands per transaction: The default transaction script issues seven commands per transaction:
</para> </para>
<orderedlist> <orderedlist>
<listitem><para><literal>BEGIN;</literal></para></listitem> <listitem><para><literal>BEGIN;</literal></para></listitem>
<listitem><para><literal>UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;</literal></para></listitem> <listitem><para><literal>UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;</literal></para></listitem>
<listitem><para><literal>SELECT abalance FROM pgbench_accounts WHERE aid = :aid;</literal></para></listitem> <listitem><para><literal>SELECT abalance FROM pgbench_accounts WHERE aid = :aid;</literal></para></listitem>
<listitem><para><literal>UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;</literal></para></listitem> <listitem><para><literal>UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;</literal></para></listitem>
<listitem><para><literal>UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid;</literal></para></listitem> <listitem><para><literal>UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid;</literal></para></listitem>
<listitem><para><literal>INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta, CURRENT_TIMESTAMP);</literal></para></listitem> <listitem><para><literal>INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta, CURRENT_TIMESTAMP);</literal></para></listitem>
<listitem><para><literal>END;</literal></para></listitem> <listitem><para><literal>END;</literal></para></listitem>
</orderedlist> </orderedlist>
<para> <para>
If you specify <literal>-N</>, steps 4 and 5 aren't included in the If you specify <literal>-N</>, steps 4 and 5 aren't included in the
transaction. If you specify <literal>-S</>, only the <command>SELECT</> is transaction. If you specify <literal>-S</>, only the <command>SELECT</> is
issued. issued.
</para> </para>
</sect2> </sect2>
<sect2> <sect2>
<title>Custom Scripts</title> <title>Custom Scripts</title>
<para> <para>
<application>pgbench</application> has support for running custom <application>pgbench</application> has support for running custom
benchmark scenarios by replacing the default transaction script benchmark scenarios by replacing the default transaction script
(described above) with a transaction script read from a file (described above) with a transaction script read from a file
(<literal>-f</literal> option). In this case a <quote>transaction</> (<literal>-f</literal> option). In this case a <quote>transaction</>
counts as one execution of a script file. You can even specify counts as one execution of a script file. You can even specify
multiple scripts (multiple <literal>-f</literal> options), in which multiple scripts (multiple <literal>-f</literal> options), in which
case a random one of the scripts is chosen each time a client session case a random one of the scripts is chosen each time a client session
starts a new transaction. starts a new transaction.
</para> </para>
<para> <para>
The format of a script file is one SQL command per line; multi-line The format of a script file is one SQL command per line; multi-line
SQL commands are not supported. Empty lines and lines beginning with SQL commands are not supported. Empty lines and lines beginning with
<literal>--</> are ignored. Script file lines can also be <literal>--</> are ignored. Script file lines can also be
<quote>meta commands</>, which are interpreted by <application>pgbench</> <quote>meta commands</>, which are interpreted by <application>pgbench</>
itself, as described below. itself, as described below.
</para> </para>
<para> <para>
There is a simple variable-substitution facility for script files. There is a simple variable-substitution facility for script files.
Variables can be set by the command-line <literal>-D</> option, Variables can be set by the command-line <literal>-D</> option,
explained above, or by the meta commands explained below. explained above, or by the meta commands explained below.
In addition to any variables preset by <literal>-D</> command-line options, In addition to any variables preset by <literal>-D</> command-line options,
the variable <literal>scale</> is preset to the current scale factor. the variable <literal>scale</> is preset to the current scale factor.
Once set, a variable's Once set, a variable's
value can be inserted into a SQL command by writing value can be inserted into a SQL command by writing
<literal>:</><replaceable>variablename</>. When running more than <literal>:</><replaceable>variablename</>. When running more than
one client session, each session has its own set of variables. one client session, each session has its own set of variables.
</para> </para>
<para> <para>
Script file meta commands begin with a backslash (<literal>\</>). Script file meta commands begin with a backslash (<literal>\</>).
Arguments to a meta command are separated by white space. Arguments to a meta command are separated by white space.
These meta commands are supported: These meta commands are supported:
</para> </para>
<variablelist> <variablelist>
<varlistentry> <varlistentry>
<term> <term>
<literal>\set <replaceable>varname</> <replaceable>operand1</> [ <replaceable>operator</> <replaceable>operand2</> ]</literal> <literal>\set <replaceable>varname</> <replaceable>operand1</> [ <replaceable>operator</> <replaceable>operand2</> ]</literal>
</term> </term>
<listitem> <listitem>
<para> <para>
Sets variable <replaceable>varname</> to a calculated integer value. Sets variable <replaceable>varname</> to a calculated integer value.
Each <replaceable>operand</> is either an integer constant or a Each <replaceable>operand</> is either an integer constant or a
<literal>:</><replaceable>variablename</> reference to a variable <literal>:</><replaceable>variablename</> reference to a variable
having an integer value. The <replaceable>operator</> can be having an integer value. The <replaceable>operator</> can be
<literal>+</>, <literal>-</>, <literal>*</>, or <literal>/</>. <literal>+</>, <literal>-</>, <literal>*</>, or <literal>/</>.
</para> </para>
<para> <para>
Example: Example:
<programlisting> <programlisting>
\set ntellers 10 * :scale \set ntellers 10 * :scale
</programlisting> </programlisting>
</para> </para>
</listitem> </listitem>
</varlistentry> </varlistentry>
<varlistentry> <varlistentry>
<term> <term>
<literal>\setrandom <replaceable>varname</> <replaceable>min</> <replaceable>max</></literal> <literal>\setrandom <replaceable>varname</> <replaceable>min</> <replaceable>max</></literal>
</term> </term>
<listitem> <listitem>
<para> <para>
Sets variable <replaceable>varname</> to a random integer value Sets variable <replaceable>varname</> to a random integer value
between the limits <replaceable>min</> and <replaceable>max</> inclusive. between the limits <replaceable>min</> and <replaceable>max</> inclusive.
Each limit can be either an integer constant or a Each limit can be either an integer constant or a
<literal>:</><replaceable>variablename</> reference to a variable <literal>:</><replaceable>variablename</> reference to a variable
having an integer value. having an integer value.
</para> </para>
<para> <para>
Example: Example:
<programlisting> <programlisting>
\setrandom aid 1 :naccounts \setrandom aid 1 :naccounts
</programlisting> </programlisting>
</para> </para>
</listitem> </listitem>
</varlistentry> </varlistentry>
<varlistentry> <varlistentry>
<term> <term>
<literal>\sleep <replaceable>number</> [ us | ms | s ]</literal> <literal>\sleep <replaceable>number</> [ us | ms | s ]</literal>
</term> </term>
<listitem> <listitem>
<para> <para>
Causes script execution to sleep for the specified duration in Causes script execution to sleep for the specified duration in
microseconds (<literal>us</>), milliseconds (<literal>ms</>) or seconds microseconds (<literal>us</>), milliseconds (<literal>ms</>) or seconds
(<literal>s</>). If the unit is omitted then seconds are the default. (<literal>s</>). If the unit is omitted then seconds are the default.
<replaceable>number</> can be either an integer constant or a <replaceable>number</> can be either an integer constant or a
<literal>:</><replaceable>variablename</> reference to a variable <literal>:</><replaceable>variablename</> reference to a variable
having an integer value. having an integer value.
</para> </para>
<para> <para>
Example: Example:
<programlisting> <programlisting>
\sleep 10 ms \sleep 10 ms
</programlisting> </programlisting>
</para> </para>
</listitem> </listitem>
</varlistentry> </varlistentry>
<varlistentry> <varlistentry>
<term> <term>
<literal>\setshell <replaceable>varname</> <replaceable>command</> [ <replaceable>argument</> ... ]</literal> <literal>\setshell <replaceable>varname</> <replaceable>command</> [ <replaceable>argument</> ... ]</literal>
</term> </term>
<listitem> <listitem>
<para> <para>
Sets variable <replaceable>varname</> to the result of the shell command Sets variable <replaceable>varname</> to the result of the shell command
<replaceable>command</>. The command must return an integer value <replaceable>command</>. The command must return an integer value
through its standard output. through its standard output.
</para> </para>
<para> <para>
<replaceable>argument</> can be either a text constant or a <replaceable>argument</> can be either a text constant or a
<literal>:</><replaceable>variablename</> reference to a variable of <literal>:</><replaceable>variablename</> reference to a variable of
any types. If you want to use <replaceable>argument</> starting with any types. If you want to use <replaceable>argument</> starting with
colons, you need to add an additional colon at the beginning of colons, you need to add an additional colon at the beginning of
<replaceable>argument</>. <replaceable>argument</>.
</para> </para>
<para> <para>
Example: Example:
<programlisting> <programlisting>
\setshell variable_to_be_assigned command literal_argument :variable ::literal_starting_with_colon \setshell variable_to_be_assigned command literal_argument :variable ::literal_starting_with_colon
</programlisting> </programlisting>
</para> </para>
</listitem> </listitem>
</varlistentry> </varlistentry>
<varlistentry> <varlistentry>
<term> <term>
<literal>\shell <replaceable>command</> [ <replaceable>argument</> ... ]</literal> <literal>\shell <replaceable>command</> [ <replaceable>argument</> ... ]</literal>
</term> </term>
<listitem> <listitem>
<para> <para>
Same as <literal>\setshell</literal>, but the result is ignored. Same as <literal>\setshell</literal>, but the result is ignored.
</para> </para>
<para> <para>
Example: Example:
<programlisting> <programlisting>
\shell command literal_argument :variable ::literal_starting_with_colon \shell command literal_argument :variable ::literal_starting_with_colon
</programlisting> </programlisting>
</para> </para>
</listitem> </listitem>
</varlistentry> </varlistentry>
</variablelist> </variablelist>
<para> <para>
As an example, the full definition of the built-in TPC-B-like As an example, the full definition of the built-in TPC-B-like
transaction is: transaction is:
<programlisting> <programlisting>
\set nbranches :scale \set nbranches :scale
\set ntellers 10 * :scale \set ntellers 10 * :scale
\set naccounts 100000 * :scale \set naccounts 100000 * :scale
\setrandom aid 1 :naccounts \setrandom aid 1 :naccounts
\setrandom bid 1 :nbranches \setrandom bid 1 :nbranches
\setrandom tid 1 :ntellers \setrandom tid 1 :ntellers
\setrandom delta -5000 5000 \setrandom delta -5000 5000
BEGIN; BEGIN;
UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid; UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;
SELECT abalance FROM pgbench_accounts WHERE aid = :aid; SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid; UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;
UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid; UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid;
INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta, CURRENT_TIMESTAMP); INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta, CURRENT_TIMESTAMP);
END; END;
</programlisting> </programlisting>
This script allows each iteration of the transaction to reference This script allows each iteration of the transaction to reference
different, randomly-chosen rows. (This example also shows why it's different, randomly-chosen rows. (This example also shows why it's
important for each client session to have its own variables &mdash; important for each client session to have its own variables &mdash;
otherwise they'd not be independently touching different rows.) otherwise they'd not be independently touching different rows.)
</para> </para>
</sect2> </sect2>
<sect2> <sect2>
<title>Per-transaction logging</title> <title>Per-transaction logging</title>
<para> <para>
With the <literal>-l</> option, <application>pgbench</> writes the time With the <literal>-l</> option, <application>pgbench</> writes the time
taken by each transaction to a logfile. The logfile will be named taken by each transaction to a logfile. The logfile will be named
<filename>pgbench_log.<replaceable>nnn</></filename>, where <filename>pgbench_log.<replaceable>nnn</></filename>, where
<replaceable>nnn</> is the PID of the pgbench process. <replaceable>nnn</> is the PID of the pgbench process.
If the <literal>-j</> option is 2 or higher, creating multiple worker If the <literal>-j</> option is 2 or higher, creating multiple worker
threads, each will have its own log file. The first worker will use the threads, each will have its own log file. The first worker will use the
the same name for its log file as in the standard single worker case. the same name for its log file as in the standard single worker case.
The additional log files for the other workers will be named The additional log files for the other workers will be named
<filename>pgbench_log.<replaceable>nnn</>.<replaceable>mmm</></filename>, <filename>pgbench_log.<replaceable>nnn</>.<replaceable>mmm</></filename>,
where <replaceable>mmm</> is a sequential number for each worker starting where <replaceable>mmm</> is a sequential number for each worker starting
with 1. with 1.
</para> </para>
<para> <para>
The format of the log is: The format of the log is:
<programlisting> <programlisting>
<replaceable>client_id</> <replaceable>transaction_no</> <replaceable>time</> <replaceable>file_no</> <replaceable>time_epoch</> <replaceable>time_us</> <replaceable>client_id</> <replaceable>transaction_no</> <replaceable>time</> <replaceable>file_no</> <replaceable>time_epoch</> <replaceable>time_us</>
</programlisting> </programlisting>
where <replaceable>time</> is the elapsed transaction time in microseconds, where <replaceable>time</> is the elapsed transaction time in microseconds,
<replaceable>file_no</> identifies which script file was used <replaceable>file_no</> identifies which script file was used
(useful when multiple scripts were specified with <literal>-f</>), (useful when multiple scripts were specified with <literal>-f</>),
and <replaceable>time_epoch</>/<replaceable>time_us</> are a and <replaceable>time_epoch</>/<replaceable>time_us</> are a
UNIX epoch format timestamp and an offset UNIX epoch format timestamp and an offset
in microseconds (suitable for creating a ISO 8601 in microseconds (suitable for creating a ISO 8601
timestamp with fractional seconds) showing when timestamp with fractional seconds) showing when
the transaction completed. the transaction completed.
</para> </para>
<para> <para>
Here are example outputs: Here are example outputs:
<programlisting> <programlisting>
0 199 2241 0 1175850568 995598 0 199 2241 0 1175850568 995598
0 200 2465 0 1175850568 998079 0 200 2465 0 1175850568 998079
0 201 2513 0 1175850569 608 0 201 2513 0 1175850569 608
0 202 2038 0 1175850569 2663 0 202 2038 0 1175850569 2663
</programlisting> </programlisting>
</para> </para>
</sect2> </sect2>
<sect2> <sect2>
<title>Good Practices</title> <title>Good Practices</title>
<para> <para>
It is very easy to use <application>pgbench</> to produce completely It is very easy to use <application>pgbench</> to produce completely
meaningless numbers. Here are some guidelines to help you get useful meaningless numbers. Here are some guidelines to help you get useful
results. results.
</para> </para>
<para> <para>
In the first place, <emphasis>never</> believe any test that runs In the first place, <emphasis>never</> believe any test that runs
for only a few seconds. Use the <literal>-t</> or <literal>-T</> option for only a few seconds. Use the <literal>-t</> or <literal>-T</> option
to make the run last at least a few minutes, so as to average out noise. to make the run last at least a few minutes, so as to average out noise.
In some cases you could need hours to get numbers that are reproducible. In some cases you could need hours to get numbers that are reproducible.
It's a good idea to try the test run a few times, to find out if your It's a good idea to try the test run a few times, to find out if your
numbers are reproducible or not. numbers are reproducible or not.
</para> </para>
<para> <para>
For the default TPC-B-like test scenario, the initialization scale factor For the default TPC-B-like test scenario, the initialization scale factor
(<literal>-s</>) should be at least as large as the largest number of (<literal>-s</>) should be at least as large as the largest number of
clients you intend to test (<literal>-c</>); else you'll mostly be clients you intend to test (<literal>-c</>); else you'll mostly be
measuring update contention. There are only <literal>-s</> rows in measuring update contention. There are only <literal>-s</> rows in
the <structname>pgbench_branches</> table, and every transaction wants to the <structname>pgbench_branches</> table, and every transaction wants to
update one of them, so <literal>-c</> values in excess of <literal>-s</> update one of them, so <literal>-c</> values in excess of <literal>-s</>
will undoubtedly result in lots of transactions blocked waiting for will undoubtedly result in lots of transactions blocked waiting for
other transactions. other transactions.
</para> </para>
<para> <para>
The default test scenario is also quite sensitive to how long it's been The default test scenario is also quite sensitive to how long it's been
since the tables were initialized: accumulation of dead rows and dead space since the tables were initialized: accumulation of dead rows and dead space
in the tables changes the results. To understand the results you must keep in the tables changes the results. To understand the results you must keep
track of the total number of updates and when vacuuming happens. If track of the total number of updates and when vacuuming happens. If
autovacuum is enabled it can result in unpredictable changes in measured autovacuum is enabled it can result in unpredictable changes in measured
performance. performance.
</para> </para>
<para> <para>
A limitation of <application>pgbench</> is that it can itself become A limitation of <application>pgbench</> is that it can itself become
the bottleneck when trying to test a large number of client sessions. the bottleneck when trying to test a large number of client sessions.
This can be alleviated by running <application>pgbench</> on a different This can be alleviated by running <application>pgbench</> on a different
machine from the database server, although low network latency will be machine from the database server, although low network latency will be
essential. It might even be useful to run several <application>pgbench</> essential. It might even be useful to run several <application>pgbench</>
instances concurrently, on several client machines, against the same instances concurrently, on several client machines, against the same
database server. database server.
</para> </para>
</sect2> </sect2>
</sect1> </sect1>
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