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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>pgbench</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="app-pgbasebackup.html" title="pg_basebackup" /><link rel="next" href="app-pgconfig.html" title="pg_config" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center"><span class="application">pgbench</span></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="app-pgbasebackup.html" title="pg_basebackup">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="reference-client.html" title="PostgreSQL Client Applications">Up</a></td><th width="60%" align="center">PostgreSQL Client Applications</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="app-pgconfig.html" title="pg_config">Next</a></td></tr></table><hr /></div><div class="refentry" id="PGBENCH"><div class="titlepage"></div><a id="id-1.9.4.11.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle"><span class="application">pgbench</span></span></h2><p>pgbench — run a benchmark test on <span class="productname">PostgreSQL</span></p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p id="id-1.9.4.11.4.1"><code class="command">pgbench</code> <code class="option">-i</code> [<em class="replaceable"><code>option</code></em>...] [<em class="replaceable"><code>dbname</code></em>]</p></div><div class="cmdsynopsis"><p id="id-1.9.4.11.4.2"><code class="command">pgbench</code> [<em class="replaceable"><code>option</code></em>...] [<em class="replaceable"><code>dbname</code></em>]</p></div></div><div class="refsect1" id="id-1.9.4.11.5"><h2>Description</h2><p>
<span class="application">pgbench</span> is a simple program for running benchmark
tests on <span class="productname">PostgreSQL</span>. It runs the same sequence of SQL
commands over and over, possibly in multiple concurrent database sessions,
and then calculates the average transaction rate (transactions per second).
By default, <span class="application">pgbench</span> tests a scenario that is
loosely based on TPC-B, involving five <code class="command">SELECT</code>,
<code class="command">UPDATE</code>, and <code class="command">INSERT</code> commands per transaction.
However, it is easy to test other cases by writing your own transaction
script files.
</p><p>
Typical output from <span class="application">pgbench</span> looks like:
</p><pre class="screen">
transaction type: <builtin: TPC-B (sort of)>
scaling factor: 10
query mode: simple
number of clients: 10
number of threads: 1
maximum number of tries: 1
number of transactions per client: 1000
number of transactions actually processed: 10000/10000
number of failed transactions: 0 (0.000%)
latency average = 11.013 ms
latency stddev = 7.351 ms
initial connection time = 45.758 ms
tps = 896.967014 (without initial connection time)
</pre><p>
The first seven lines report some of the most important parameter
settings.
The sixth line reports the maximum number of tries for transactions with
serialization or deadlock errors (see <a class="xref" href="pgbench.html#FAILURES-AND-RETRIES" title="Failures and Serialization/Deadlock Retries">Failures and Serialization/Deadlock Retries</a>
for more information).
The eighth line reports the number of transactions completed
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
failed before completion or some SQL command(s) failed. (In
<code class="option">-T</code> mode, only the actual number of transactions is printed.)
The next line reports the number of failed transactions due to
serialization or deadlock errors (see <a class="xref" href="pgbench.html#FAILURES-AND-RETRIES" title="Failures and Serialization/Deadlock Retries">Failures and Serialization/Deadlock Retries</a>
for more information).
The last line reports the number of transactions per second.
</p><p>
The default TPC-B-like transaction test requires specific tables to be
set up beforehand. <span class="application">pgbench</span> should be invoked with
the <code class="option">-i</code> (initialize) option to create and populate these
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.)
Initialization looks like:
</p><pre class="programlisting">
pgbench -i [<span class="optional"> <em class="replaceable"><code>other-options</code></em> </span>] <em class="replaceable"><code>dbname</code></em>
</pre><p>
where <em class="replaceable"><code>dbname</code></em> is the name of the already-created
database to test in. (You may also need <code class="option">-h</code>,
<code class="option">-p</code>, and/or <code class="option">-U</code> options to specify how to
connect to the database server.)
</p><div class="caution"><h3 class="title">Caution</h3><p>
<code class="literal">pgbench -i</code> creates four tables <code class="structname">pgbench_accounts</code>,
<code class="structname">pgbench_branches</code>, <code class="structname">pgbench_history</code>, and
<code class="structname">pgbench_tellers</code>,
destroying any existing tables of these names.
Be very careful to use another database if you have tables having these
names!
</p></div><p>
At the default <span class="quote">“<span class="quote">scale factor</span>”</span> of 1, the tables initially
contain this many rows:
</p><pre class="screen">
table # of rows
---------------------------------
pgbench_branches 1
pgbench_tellers 10
pgbench_accounts 100000
pgbench_history 0
</pre><p>
You can (and, for most purposes, probably should) increase the number
of rows by using the <code class="option">-s</code> (scale factor) option. The
<code class="option">-F</code> (fillfactor) option might also be used at this point.
</p><p>
Once you have done the necessary setup, you can run your benchmark
with a command that doesn't include <code class="option">-i</code>, that is
</p><pre class="programlisting">
pgbench [<span class="optional"> <em class="replaceable"><code>options</code></em> </span>] <em class="replaceable"><code>dbname</code></em>
</pre><p>
In nearly all cases, you'll need some options to make a useful test.
The most important options are <code class="option">-c</code> (number of clients),
<code class="option">-t</code> (number of transactions), <code class="option">-T</code> (time limit),
and <code class="option">-f</code> (specify a custom script file).
See below for a full list.
</p></div><div class="refsect1" id="id-1.9.4.11.6"><h2>Options</h2><p>
The following is divided into three subsections. Different options are
used during database initialization and while running benchmarks, but some
options are useful in both cases.
</p><div class="refsect2" id="PGBENCH-INIT-OPTIONS"><h3>Initialization Options</h3><p>
<span class="application">pgbench</span> accepts the following command-line
initialization arguments:
</p><div class="variablelist"><dl class="variablelist"><dt id="PGBENCH-OPTION-DBNAME"><span class="term"><em class="replaceable"><code>dbname</code></em></span> <a href="#PGBENCH-OPTION-DBNAME" class="id_link">#</a></dt><dd><p>
Specifies the name of the database to test in. If this is
not specified, the environment variable
<code class="envar">PGDATABASE</code> is used. If that is not set, the
user name specified for the connection is used.
</p></dd><dt id="PGBENCH-OPTION-INITIALIZE"><span class="term"><code class="option">-i</code><br /></span><span class="term"><code class="option">--initialize</code></span> <a href="#PGBENCH-OPTION-INITIALIZE" class="id_link">#</a></dt><dd><p>
Required to invoke initialization mode.
</p></dd><dt id="PGBENCH-OPTION-INIT-STEPS"><span class="term"><code class="option">-I <em class="replaceable"><code>init_steps</code></em></code><br /></span><span class="term"><code class="option">--init-steps=<em class="replaceable"><code>init_steps</code></em></code></span> <a href="#PGBENCH-OPTION-INIT-STEPS" class="id_link">#</a></dt><dd><p>
Perform just a selected set of the normal initialization steps.
<em class="replaceable"><code>init_steps</code></em> specifies the
initialization steps to be performed, using one character per step.
Each step is invoked in the specified order.
The default is <code class="literal">dtgvp</code>.
The available steps are:
</p><div class="variablelist"><dl class="variablelist"><dt id="PGBENCH-OPTION-INIT-STEPS-D"><span class="term"><code class="literal">d</code> (Drop)</span> <a href="#PGBENCH-OPTION-INIT-STEPS-D" class="id_link">#</a></dt><dd><p>
Drop any existing <span class="application">pgbench</span> tables.
</p></dd><dt id="PGBENCH-OPTION-INIT-STEPS-T"><span class="term"><code class="literal">t</code> (create Tables)</span> <a href="#PGBENCH-OPTION-INIT-STEPS-T" class="id_link">#</a></dt><dd><p>
Create the tables used by the
standard <span class="application">pgbench</span> scenario, namely
<code class="structname">pgbench_accounts</code>,
<code class="structname">pgbench_branches</code>,
<code class="structname">pgbench_history</code>, and
<code class="structname">pgbench_tellers</code>.
</p></dd><dt id="PGBENCH-OPTION-INIT-STEPS-G"><span class="term"><code class="literal">g</code> or <code class="literal">G</code> (Generate data, client-side or server-side)</span> <a href="#PGBENCH-OPTION-INIT-STEPS-G" class="id_link">#</a></dt><dd><p>
Generate data and load it into the standard tables,
replacing any data already present.
</p><p>
With <code class="literal">g</code> (client-side data generation),
data is generated in <code class="command">pgbench</code> client and then
sent to the server. This uses the client/server bandwidth
extensively through a <code class="command">COPY</code>.
<code class="command">pgbench</code> uses the FREEZE option with version 14 or later
of <span class="productname">PostgreSQL</span> to speed up
subsequent <code class="command">VACUUM</code>, unless partitions are enabled.
Using <code class="literal">g</code> causes logging to print one message
every 100,000 rows while generating data for the
<code class="structname">pgbench_accounts</code> table.
</p><p>
With <code class="literal">G</code> (server-side data generation),
only small queries are sent from the <code class="command">pgbench</code>
client and then data is actually generated in the server.
No significant bandwidth is required for this variant, but
the server will do more work.
Using <code class="literal">G</code> causes logging not to print any progress
message while generating data.
</p><p>
The default initialization behavior uses client-side data
generation (equivalent to <code class="literal">g</code>).
</p></dd><dt id="PGBENCH-OPTION-INIT-STEPS-V"><span class="term"><code class="literal">v</code> (Vacuum)</span> <a href="#PGBENCH-OPTION-INIT-STEPS-V" class="id_link">#</a></dt><dd><p>
Invoke <code class="command">VACUUM</code> on the standard tables.
</p></dd><dt id="PGBENCH-OPTION-INIT-STEPS-P"><span class="term"><code class="literal">p</code> (create Primary keys)</span> <a href="#PGBENCH-OPTION-INIT-STEPS-P" class="id_link">#</a></dt><dd><p>
Create primary key indexes on the standard tables.
</p></dd><dt id="PGBENCH-OPTION-INIT-STEPS-F"><span class="term"><code class="literal">f</code> (create Foreign keys)</span> <a href="#PGBENCH-OPTION-INIT-STEPS-F" class="id_link">#</a></dt><dd><p>
Create foreign key constraints between the standard tables.
(Note that this step is not performed by default.)
</p></dd></dl></div></dd><dt id="PGBENCH-OPTION-FILLFACTOR"><span class="term"><code class="option">-F</code> <em class="replaceable"><code>fillfactor</code></em><br /></span><span class="term"><code class="option">--fillfactor=</code><em class="replaceable"><code>fillfactor</code></em></span> <a href="#PGBENCH-OPTION-FILLFACTOR" class="id_link">#</a></dt><dd><p>
Create the <code class="structname">pgbench_accounts</code>,
<code class="structname">pgbench_tellers</code> and
<code class="structname">pgbench_branches</code> tables with the given fillfactor.
Default is 100.
</p></dd><dt id="PGBENCH-OPTION-NO-VACUUM-INIT"><span class="term"><code class="option">-n</code><br /></span><span class="term"><code class="option">--no-vacuum</code></span> <a href="#PGBENCH-OPTION-NO-VACUUM-INIT" class="id_link">#</a></dt><dd><p>
Perform no vacuuming during initialization.
(This option suppresses the <code class="literal">v</code> initialization step,
even if it was specified in <code class="option">-I</code>.)
</p></dd><dt id="PGBENCH-OPTION-QUIET"><span class="term"><code class="option">-q</code><br /></span><span class="term"><code class="option">--quiet</code></span> <a href="#PGBENCH-OPTION-QUIET" class="id_link">#</a></dt><dd><p>
Switch logging to quiet mode, producing only one progress message per 5
seconds. The default logging prints one message each 100,000 rows, which
often outputs many lines per second (especially on good hardware).
</p><p>
This setting has no effect if <code class="literal">G</code> is specified
in <code class="option">-I</code>.
</p></dd><dt id="PGBENCH-OPTION-SCALE-INIT"><span class="term"><code class="option">-s</code> <em class="replaceable"><code>scale_factor</code></em><br /></span><span class="term"><code class="option">--scale=</code><em class="replaceable"><code>scale_factor</code></em></span> <a href="#PGBENCH-OPTION-SCALE-INIT" class="id_link">#</a></dt><dd><p>
Multiply the number of rows generated by the scale factor.
For example, <code class="literal">-s 100</code> will create 10,000,000 rows
in the <code class="structname">pgbench_accounts</code> table. Default is 1.
When the scale is 20,000 or larger, the columns used to
hold account identifiers (<code class="structfield">aid</code> columns)
will switch to using larger integers (<code class="type">bigint</code>),
in order to be big enough to hold the range of account
identifiers.
</p></dd><dt id="PGBENCH-OPTION-FOREIGN-KEYS"><span class="term"><code class="option">--foreign-keys</code></span> <a href="#PGBENCH-OPTION-FOREIGN-KEYS" class="id_link">#</a></dt><dd><p>
Create foreign key constraints between the standard tables.
(This option adds the <code class="literal">f</code> step to the initialization
step sequence, if it is not already present.)
</p></dd><dt id="PGBENCH-OPTION-INDEX-TABLESPACE"><span class="term"><code class="option">--index-tablespace=<em class="replaceable"><code>index_tablespace</code></em></code></span> <a href="#PGBENCH-OPTION-INDEX-TABLESPACE" class="id_link">#</a></dt><dd><p>
Create indexes in the specified tablespace, rather than the default
tablespace.
</p></dd><dt id="PGBENCH-OPTION-PARTITION-METHOD"><span class="term"><code class="option">--partition-method=<em class="replaceable"><code>NAME</code></em></code></span> <a href="#PGBENCH-OPTION-PARTITION-METHOD" class="id_link">#</a></dt><dd><p>
Create a partitioned <code class="literal">pgbench_accounts</code> table with
<em class="replaceable"><code>NAME</code></em> method.
Expected values are <code class="literal">range</code> or <code class="literal">hash</code>.
This option requires that <code class="option">--partitions</code> is set to non-zero.
If unspecified, default is <code class="literal">range</code>.
</p></dd><dt id="PGBENCH-OPTION-PARTITIONS"><span class="term"><code class="option">--partitions=<em class="replaceable"><code>NUM</code></em></code></span> <a href="#PGBENCH-OPTION-PARTITIONS" class="id_link">#</a></dt><dd><p>
Create a partitioned <code class="literal">pgbench_accounts</code> table with
<em class="replaceable"><code>NUM</code></em> partitions of nearly equal size for
the scaled number of accounts.
Default is <code class="literal">0</code>, meaning no partitioning.
</p></dd><dt id="PGBENCH-OPTION-TABLESPACE"><span class="term"><code class="option">--tablespace=<em class="replaceable"><code>tablespace</code></em></code></span> <a href="#PGBENCH-OPTION-TABLESPACE" class="id_link">#</a></dt><dd><p>
Create tables in the specified tablespace, rather than the default
tablespace.
</p></dd><dt id="PGBENCH-OPTION-UNLOGGED-TABLES"><span class="term"><code class="option">--unlogged-tables</code></span> <a href="#PGBENCH-OPTION-UNLOGGED-TABLES" class="id_link">#</a></dt><dd><p>
Create all tables as unlogged tables, rather than permanent tables.
</p></dd></dl></div><p>
</p></div><div class="refsect2" id="PGBENCH-RUN-OPTIONS"><h3>Benchmarking Options</h3><p>
<span class="application">pgbench</span> accepts the following command-line
benchmarking arguments:
</p><div class="variablelist"><dl class="variablelist"><dt id="PGBENCH-OPTION-BUILTIN"><span class="term"><code class="option">-b</code> <em class="replaceable"><code>scriptname[@weight]</code></em><br /></span><span class="term"><code class="option">--builtin</code>=<em class="replaceable"><code>scriptname[@weight]</code></em></span> <a href="#PGBENCH-OPTION-BUILTIN" class="id_link">#</a></dt><dd><p>
Add the specified built-in script to the list of scripts to be executed.
Available built-in scripts are: <code class="literal">tpcb-like</code>,
<code class="literal">simple-update</code> and <code class="literal">select-only</code>.
Unambiguous prefixes of built-in names are accepted.
With the special name <code class="literal">list</code>, show the list of built-in scripts
and exit immediately.
</p><p>
Optionally, write an integer weight after <code class="literal">@</code> to
adjust the probability of selecting this script versus other ones.
The default weight is 1.
See below for details.
</p></dd><dt id="PGBENCH-OPTION-CLIENT"><span class="term"><code class="option">-c</code> <em class="replaceable"><code>clients</code></em><br /></span><span class="term"><code class="option">--client=</code><em class="replaceable"><code>clients</code></em></span> <a href="#PGBENCH-OPTION-CLIENT" class="id_link">#</a></dt><dd><p>
Number of clients simulated, that is, number of concurrent database
sessions. Default is 1.
</p></dd><dt id="PGBENCH-OPTION-CONNECT"><span class="term"><code class="option">-C</code><br /></span><span class="term"><code class="option">--connect</code></span> <a href="#PGBENCH-OPTION-CONNECT" class="id_link">#</a></dt><dd><p>
Establish a new connection for each transaction, rather than
doing it just once per client session.
This is useful to measure the connection overhead.
</p></dd><dt id="PGBENCH-OPTION-DEBUG"><span class="term"><code class="option">-d</code><br /></span><span class="term"><code class="option">--debug</code></span> <a href="#PGBENCH-OPTION-DEBUG" class="id_link">#</a></dt><dd><p>
Print debugging output.
</p></dd><dt id="PGBENCH-OPTION-DEFINE"><span class="term"><code class="option">-D</code> <em class="replaceable"><code>varname</code></em><code class="literal">=</code><em class="replaceable"><code>value</code></em><br /></span><span class="term"><code class="option">--define=</code><em class="replaceable"><code>varname</code></em><code class="literal">=</code><em class="replaceable"><code>value</code></em></span> <a href="#PGBENCH-OPTION-DEFINE" class="id_link">#</a></dt><dd><p>
Define a variable for use by a custom script (see below).
Multiple <code class="option">-D</code> options are allowed.
</p></dd><dt id="PGBENCH-OPTION-FILE"><span class="term"><code class="option">-f</code> <em class="replaceable"><code>filename[@weight]</code></em><br /></span><span class="term"><code class="option">--file=</code><em class="replaceable"><code>filename[@weight]</code></em></span> <a href="#PGBENCH-OPTION-FILE" class="id_link">#</a></dt><dd><p>
Add a transaction script read from <em class="replaceable"><code>filename</code></em>
to the list of scripts to be executed.
</p><p>
Optionally, write an integer weight after <code class="literal">@</code> to
adjust the probability of selecting this script versus other ones.
The default weight is 1.
(To use a script file name that includes an <code class="literal">@</code>
character, append a weight so that there is no ambiguity, for
example <code class="literal">filen@me@1</code>.)
See below for details.
</p></dd><dt id="PGBENCH-OPTION-JOBS"><span class="term"><code class="option">-j</code> <em class="replaceable"><code>threads</code></em><br /></span><span class="term"><code class="option">--jobs=</code><em class="replaceable"><code>threads</code></em></span> <a href="#PGBENCH-OPTION-JOBS" class="id_link">#</a></dt><dd><p>
Number of worker threads within <span class="application">pgbench</span>.
Using more than one thread can be helpful on multi-CPU machines.
Clients are distributed as evenly as possible among available threads.
Default is 1.
</p></dd><dt id="PGBENCH-OPTION-LOG"><span class="term"><code class="option">-l</code><br /></span><span class="term"><code class="option">--log</code></span> <a href="#PGBENCH-OPTION-LOG" class="id_link">#</a></dt><dd><p>
Write information about each transaction to a log file.
See below for details.
</p></dd><dt id="PGBENCH-OPTION-LATENCY-LIMIT"><span class="term"><code class="option">-L</code> <em class="replaceable"><code>limit</code></em><br /></span><span class="term"><code class="option">--latency-limit=</code><em class="replaceable"><code>limit</code></em></span> <a href="#PGBENCH-OPTION-LATENCY-LIMIT" class="id_link">#</a></dt><dd><p>
Transactions that last more than <em class="replaceable"><code>limit</code></em> milliseconds
are counted and reported separately, as <em class="firstterm">late</em>.
</p><p>
When throttling is used (<code class="option">--rate=...</code>), transactions that
lag behind schedule by more than <em class="replaceable"><code>limit</code></em> ms, and thus
have no hope of meeting the latency limit, are not sent to the server
at all. They are counted and reported separately as
<em class="firstterm">skipped</em>.
</p><p>
When the <code class="option">--max-tries</code> option is used, a transaction
which fails due to a serialization anomaly or from a deadlock will not
be retried if the total time of all its tries is greater than
<em class="replaceable"><code>limit</code></em> ms. To limit only the time of tries
and not their number, use <code class="literal">--max-tries=0</code>. By
default, the option <code class="option">--max-tries</code> is set to 1 and
transactions with serialization/deadlock errors are not retried. See
<a class="xref" href="pgbench.html#FAILURES-AND-RETRIES" title="Failures and Serialization/Deadlock Retries">Failures and Serialization/Deadlock Retries</a> for more information about
retrying such transactions.
</p></dd><dt id="PGBENCH-OPTION-PROTOCOL"><span class="term"><code class="option">-M</code> <em class="replaceable"><code>querymode</code></em><br /></span><span class="term"><code class="option">--protocol=</code><em class="replaceable"><code>querymode</code></em></span> <a href="#PGBENCH-OPTION-PROTOCOL" class="id_link">#</a></dt><dd><p>
Protocol to use for submitting queries to the server:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="literal">simple</code>: use simple query protocol.</p></li><li class="listitem"><p><code class="literal">extended</code>: use extended query protocol.</p></li><li class="listitem"><p><code class="literal">prepared</code>: use extended query protocol with prepared statements.</p></li></ul></div><p>
In the <code class="literal">prepared</code> mode, <span class="application">pgbench</span>
reuses the parse analysis result starting from the second query
iteration, so <span class="application">pgbench</span> runs faster
than in other modes.
</p><p>
The default is simple query protocol. (See <a class="xref" href="protocol.html" title="Chapter 55. Frontend/Backend Protocol">Chapter 55</a>
for more information.)
</p></dd><dt id="PGBENCH-OPTION-NO-VACUUM-RUN"><span class="term"><code class="option">-n</code><br /></span><span class="term"><code class="option">--no-vacuum</code></span> <a href="#PGBENCH-OPTION-NO-VACUUM-RUN" class="id_link">#</a></dt><dd><p>
Perform no vacuuming before running the test.
This option is <span class="emphasis"><em>necessary</em></span>
if you are running a custom test scenario that does not include
the standard tables <code class="structname">pgbench_accounts</code>,
<code class="structname">pgbench_branches</code>, <code class="structname">pgbench_history</code>, and
<code class="structname">pgbench_tellers</code>.
</p></dd><dt id="PGBENCH-OPTION-SKIP-SOME-UPDATES"><span class="term"><code class="option">-N</code><br /></span><span class="term"><code class="option">--skip-some-updates</code></span> <a href="#PGBENCH-OPTION-SKIP-SOME-UPDATES" class="id_link">#</a></dt><dd><p>
Run built-in simple-update script.
Shorthand for <code class="option">-b simple-update</code>.
</p></dd><dt id="PGBENCH-OPTION-PROGRESS"><span class="term"><code class="option">-P</code> <em class="replaceable"><code>sec</code></em><br /></span><span class="term"><code class="option">--progress=</code><em class="replaceable"><code>sec</code></em></span> <a href="#PGBENCH-OPTION-PROGRESS" class="id_link">#</a></dt><dd><p>
Show progress report every <em class="replaceable"><code>sec</code></em> seconds. The report
includes the time since the beginning of the run, the TPS since the
last report, and the transaction latency average, standard deviation,
and the number of failed transactions since the last report. Under
throttling (<code class="option">-R</code>), the latency is computed with respect
to the transaction scheduled start time, not the actual transaction
beginning time, thus it also includes the average schedule lag time.
When <code class="option">--max-tries</code> is used to enable transaction retries
after serialization/deadlock errors, the report includes the number of
retried transactions and the sum of all retries.
</p></dd><dt id="PGBENCH-OPTION-REPORT-LATENCIES"><span class="term"><code class="option">-r</code><br /></span><span class="term"><code class="option">--report-per-command</code></span> <a href="#PGBENCH-OPTION-REPORT-LATENCIES" class="id_link">#</a></dt><dd><p>
Report the following statistics for each command after the benchmark
finishes: the average per-statement latency (execution time from the
perspective of the client), the number of failures, and the number of
retries after serialization or deadlock errors in this command. The
report displays retry statistics only if the
<code class="option">--max-tries</code> option is not equal to 1.
</p></dd><dt id="PGBENCH-OPTION-RATE"><span class="term"><code class="option">-R</code> <em class="replaceable"><code>rate</code></em><br /></span><span class="term"><code class="option">--rate=</code><em class="replaceable"><code>rate</code></em></span> <a href="#PGBENCH-OPTION-RATE" class="id_link">#</a></dt><dd><p>
Execute transactions targeting the specified rate instead of running
as fast as possible (the default). The rate is given in transactions
per second. If the targeted rate is above the maximum possible rate,
the rate limit won't impact the results.
</p><p>
The rate is targeted by starting transactions along a
Poisson-distributed schedule time line. The expected start time
schedule moves forward based on when the client first started, not
when the previous transaction ended. That approach means that when
transactions go past their original scheduled end time, it is
possible for later ones to catch up again.
</p><p>
When throttling is active, the transaction latency reported at the
end of the run is calculated from the scheduled start times, so it
includes the time each transaction had to wait for the previous
transaction to finish. The wait time is called the schedule lag time,
and its average and maximum are also reported separately. The
transaction latency with respect to the actual transaction start time,
i.e., the time spent executing the transaction in the database, can be
computed by subtracting the schedule lag time from the reported
latency.
</p><p>
If <code class="option">--latency-limit</code> is used together with <code class="option">--rate</code>,
a transaction can lag behind so much that it is already over the
latency limit when the previous transaction ends, because the latency
is calculated from the scheduled start time. Such transactions are
not sent to the server, but are skipped altogether and counted
separately.
</p><p>
A high schedule lag time is an indication that the system cannot
process transactions at the specified rate, with the chosen number of
clients and threads. When the average transaction execution time is
longer than the scheduled interval between each transaction, each
successive transaction will fall further behind, and the schedule lag
time will keep increasing the longer the test run is. When that
happens, you will have to reduce the specified transaction rate.
</p></dd><dt id="PGBENCH-OPTION-SCALE-RUN"><span class="term"><code class="option">-s</code> <em class="replaceable"><code>scale_factor</code></em><br /></span><span class="term"><code class="option">--scale=</code><em class="replaceable"><code>scale_factor</code></em></span> <a href="#PGBENCH-OPTION-SCALE-RUN" class="id_link">#</a></dt><dd><p>
Report the specified scale factor in <span class="application">pgbench</span>'s
output. With the built-in tests, this is not necessary; the
correct scale factor will be detected by counting the number of
rows in the <code class="structname">pgbench_branches</code> table.
However, when testing only custom benchmarks (<code class="option">-f</code> option),
the scale factor will be reported as 1 unless this option is used.
</p></dd><dt id="PGBENCH-OPTION-SELECT-ONLY"><span class="term"><code class="option">-S</code><br /></span><span class="term"><code class="option">--select-only</code></span> <a href="#PGBENCH-OPTION-SELECT-ONLY" class="id_link">#</a></dt><dd><p>
Run built-in select-only script.
Shorthand for <code class="option">-b select-only</code>.
</p></dd><dt id="PGBENCH-OPTION-TRANSACTIONS"><span class="term"><code class="option">-t</code> <em class="replaceable"><code>transactions</code></em><br /></span><span class="term"><code class="option">--transactions=</code><em class="replaceable"><code>transactions</code></em></span> <a href="#PGBENCH-OPTION-TRANSACTIONS" class="id_link">#</a></dt><dd><p>
Number of transactions each client runs. Default is 10.
</p></dd><dt id="PGBENCH-OPTION-TIME"><span class="term"><code class="option">-T</code> <em class="replaceable"><code>seconds</code></em><br /></span><span class="term"><code class="option">--time=</code><em class="replaceable"><code>seconds</code></em></span> <a href="#PGBENCH-OPTION-TIME" class="id_link">#</a></dt><dd><p>
Run the test for this many seconds, rather than a fixed number of
transactions per client. <code class="option">-t</code> and
<code class="option">-T</code> are mutually exclusive.
</p></dd><dt id="PGBENCH-OPTION-VACUUM-ALL"><span class="term"><code class="option">-v</code><br /></span><span class="term"><code class="option">--vacuum-all</code></span> <a href="#PGBENCH-OPTION-VACUUM-ALL" class="id_link">#</a></dt><dd><p>
Vacuum all four standard tables before running the test.
With neither <code class="option">-n</code> nor <code class="option">-v</code>, <span class="application">pgbench</span> will vacuum the
<code class="structname">pgbench_tellers</code> and <code class="structname">pgbench_branches</code>
tables, and will truncate <code class="structname">pgbench_history</code>.
</p></dd><dt id="PGBENCH-OPTION-AGGREGATE-INTERVAL"><span class="term"><code class="option">--aggregate-interval=<em class="replaceable"><code>seconds</code></em></code></span> <a href="#PGBENCH-OPTION-AGGREGATE-INTERVAL" class="id_link">#</a></dt><dd><p>
Length of aggregation interval (in seconds). May be used only
with <code class="option">-l</code> option. With this option, the log contains
per-interval summary data, as described below.
</p></dd><dt id="PGBENCH-OPTION-FAILURES-DETAILED"><span class="term"><code class="option">--failures-detailed</code></span> <a href="#PGBENCH-OPTION-FAILURES-DETAILED" class="id_link">#</a></dt><dd><p>
Report failures in per-transaction and aggregation logs, as well as in
the main and per-script reports, grouped by the following types:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>serialization failures;</p></li><li class="listitem"><p>deadlock failures;</p></li></ul></div><p>
See <a class="xref" href="pgbench.html#FAILURES-AND-RETRIES" title="Failures and Serialization/Deadlock Retries">Failures and Serialization/Deadlock Retries</a> for more information.
</p></dd><dt id="PGBENCH-OPTION-LOG-PREFIX"><span class="term"><code class="option">--log-prefix=<em class="replaceable"><code>prefix</code></em></code></span> <a href="#PGBENCH-OPTION-LOG-PREFIX" class="id_link">#</a></dt><dd><p>
Set the filename prefix for the log files created by
<code class="option">--log</code>. The default is <code class="literal">pgbench_log</code>.
</p></dd><dt id="PGBENCH-OPTION-MAX-TRIES"><span class="term"><code class="option">--max-tries=<em class="replaceable"><code>number_of_tries</code></em></code></span> <a href="#PGBENCH-OPTION-MAX-TRIES" class="id_link">#</a></dt><dd><p>
Enable retries for transactions with serialization/deadlock errors and
set the maximum number of these tries. This option can be combined with
the <code class="option">--latency-limit</code> option which limits the total time
of all transaction tries; moreover, you cannot use an unlimited number
of tries (<code class="literal">--max-tries=0</code>) without
<code class="option">--latency-limit</code> or <code class="option">--time</code>.
The default value is 1 and transactions with serialization/deadlock
errors are not retried. See <a class="xref" href="pgbench.html#FAILURES-AND-RETRIES" title="Failures and Serialization/Deadlock Retries">Failures and Serialization/Deadlock Retries</a>
for more information about retrying such transactions.
</p></dd><dt id="PGBENCH-OPTION-PROGRESS-TIMESTAMP"><span class="term"><code class="option">--progress-timestamp</code></span> <a href="#PGBENCH-OPTION-PROGRESS-TIMESTAMP" class="id_link">#</a></dt><dd><p>
When showing progress (option <code class="option">-P</code>), use a timestamp
(Unix epoch) instead of the number of seconds since the
beginning of the run. The unit is in seconds, with millisecond
precision after the dot.
This helps compare logs generated by various tools.
</p></dd><dt id="PGBENCH-OPTION-RANDOM-SEED"><span class="term"><code class="option">--random-seed=</code><em class="replaceable"><code>seed</code></em></span> <a href="#PGBENCH-OPTION-RANDOM-SEED" class="id_link">#</a></dt><dd><p>
Set random generator seed. Seeds the system random number generator,
which then produces a sequence of initial generator states, one for
each thread.
Values for <em class="replaceable"><code>seed</code></em> may be:
<code class="literal">time</code> (the default, the seed is based on the current time),
<code class="literal">rand</code> (use a strong random source, failing if none
is available), or an unsigned decimal integer value.
The random generator is invoked explicitly from a pgbench script
(<code class="literal">random...</code> functions) or implicitly (for instance option
<code class="option">--rate</code> uses it to schedule transactions).
When explicitly set, the value used for seeding is shown on the terminal.
Any value allowed for <em class="replaceable"><code>seed</code></em> may also be
provided through the environment variable
<code class="literal">PGBENCH_RANDOM_SEED</code>.
To ensure that the provided seed impacts all possible uses, put this option
first or use the environment variable.
</p><p>
Setting the seed explicitly allows to reproduce a <code class="command">pgbench</code>
run exactly, as far as random numbers are concerned.
As the random state is managed per thread, this means the exact same
<code class="command">pgbench</code> run for an identical invocation if there is one
client per thread and there are no external or data dependencies.
From a statistical viewpoint reproducing runs exactly is a bad idea because
it can hide the performance variability or improve performance unduly,
e.g., by hitting the same pages as a previous run.
However, it may also be of great help for debugging, for instance
re-running a tricky case which leads to an error.
Use wisely.
</p></dd><dt id="PGBENCH-OPTION-SAMPLING-RATE"><span class="term"><code class="option">--sampling-rate=<em class="replaceable"><code>rate</code></em></code></span> <a href="#PGBENCH-OPTION-SAMPLING-RATE" class="id_link">#</a></dt><dd><p>
Sampling rate, used when writing data into the log, to reduce the
amount of log generated. If this option is given, only the specified
fraction of transactions are logged. 1.0 means all transactions will
be logged, 0.05 means only 5% of the transactions will be logged.
</p><p>
Remember to take the sampling rate into account when processing the
log file. For example, when computing TPS values, you need to multiply
the numbers accordingly (e.g., with 0.01 sample rate, you'll only get
1/100 of the actual TPS).
</p></dd><dt id="PGBENCH-OPTION-SHOW-SCRIPT"><span class="term"><code class="option">--show-script=</code><em class="replaceable"><code>scriptname</code></em></span> <a href="#PGBENCH-OPTION-SHOW-SCRIPT" class="id_link">#</a></dt><dd><p>
Show the actual code of builtin script <em class="replaceable"><code>scriptname</code></em>
on stderr, and exit immediately.
</p></dd><dt id="PGBENCH-OPTION-VERBOSE-ERRORS"><span class="term"><code class="option">--verbose-errors</code></span> <a href="#PGBENCH-OPTION-VERBOSE-ERRORS" class="id_link">#</a></dt><dd><p>
Print messages about all errors and failures (errors without retrying)
including which limit for retries was exceeded and how far it was
exceeded for the serialization/deadlock failures. (Note that in this
case the output can be significantly increased.).
See <a class="xref" href="pgbench.html#FAILURES-AND-RETRIES" title="Failures and Serialization/Deadlock Retries">Failures and Serialization/Deadlock Retries</a> for more information.
</p></dd></dl></div><p>
</p></div><div class="refsect2" id="PGBENCH-COMMON-OPTIONS"><h3>Common Options</h3><p>
<span class="application">pgbench</span> also accepts the following common command-line
arguments for connection parameters:
</p><div class="variablelist"><dl class="variablelist"><dt id="PGBENCH-OPTION-HOST"><span class="term"><code class="option">-h</code> <em class="replaceable"><code>hostname</code></em><br /></span><span class="term"><code class="option">--host=</code><em class="replaceable"><code>hostname</code></em></span> <a href="#PGBENCH-OPTION-HOST" class="id_link">#</a></dt><dd><p>
The database server's host name
</p></dd><dt id="PGBENCH-OPTION-PORT"><span class="term"><code class="option">-p</code> <em class="replaceable"><code>port</code></em><br /></span><span class="term"><code class="option">--port=</code><em class="replaceable"><code>port</code></em></span> <a href="#PGBENCH-OPTION-PORT" class="id_link">#</a></dt><dd><p>
The database server's port number
</p></dd><dt id="PGBENCH-OPTION-USERNAME"><span class="term"><code class="option">-U</code> <em class="replaceable"><code>login</code></em><br /></span><span class="term"><code class="option">--username=</code><em class="replaceable"><code>login</code></em></span> <a href="#PGBENCH-OPTION-USERNAME" class="id_link">#</a></dt><dd><p>
The user name to connect as
</p></dd><dt id="PGBENCH-OPTION-VERSION"><span class="term"><code class="option">-V</code><br /></span><span class="term"><code class="option">--version</code></span> <a href="#PGBENCH-OPTION-VERSION" class="id_link">#</a></dt><dd><p>
Print the <span class="application">pgbench</span> version and exit.
</p></dd><dt id="PGBENCH-OPTION-HELP"><span class="term"><code class="option">-?</code><br /></span><span class="term"><code class="option">--help</code></span> <a href="#PGBENCH-OPTION-HELP" class="id_link">#</a></dt><dd><p>
Show help about <span class="application">pgbench</span> command line
arguments, and exit.
</p></dd></dl></div><p>
</p></div></div><div class="refsect1" id="id-1.9.4.11.7"><h2>Exit Status</h2><p>
A successful run will exit with status 0. Exit status 1 indicates static
problems such as invalid command-line options or internal errors which
are supposed to never occur. Early errors that occur when starting
benchmark such as initial connection failures also exit with status 1.
Errors during the run such as database errors or problems in the script
will result in exit status 2. In the latter case,
<span class="application">pgbench</span> will print partial results.
</p></div><div class="refsect1" id="id-1.9.4.11.8"><h2>Environment</h2><div class="variablelist"><dl class="variablelist"><dt id="PGBENCH-ENVIRONMENT-PGDATABASE"><span class="term"><code class="envar">PGDATABASE</code><br /></span><span class="term"><code class="envar">PGHOST</code><br /></span><span class="term"><code class="envar">PGPORT</code><br /></span><span class="term"><code class="envar">PGUSER</code></span> <a href="#PGBENCH-ENVIRONMENT-PGDATABASE" class="id_link">#</a></dt><dd><p>
Default connection parameters.
</p></dd></dl></div><p>
This utility, like most other <span class="productname">PostgreSQL</span> utilities,
uses the environment variables supported by <span class="application">libpq</span>
(see <a class="xref" href="libpq-envars.html" title="34.15. Environment Variables">Section 34.15</a>).
</p><p>
The environment variable <code class="envar">PG_COLOR</code> specifies whether to use
color in diagnostic messages. Possible values are
<code class="literal">always</code>, <code class="literal">auto</code> and
<code class="literal">never</code>.
</p></div><div class="refsect1" id="id-1.9.4.11.9"><h2>Notes</h2><div class="refsect2" id="TRANSACTIONS-AND-SCRIPTS"><h3>What Is the <span class="quote">“<span class="quote">Transaction</span>”</span> Actually Performed in <span class="application">pgbench</span>?</h3><p>
<span class="application">pgbench</span> executes test scripts chosen randomly
from a specified list.
The scripts may include built-in scripts specified with <code class="option">-b</code>
and user-provided scripts specified with <code class="option">-f</code>.
Each script may be given a relative weight specified after an
<code class="literal">@</code> so as to change its selection probability.
The default weight is <code class="literal">1</code>.
Scripts with a weight of <code class="literal">0</code> are ignored.
</p><p>
The default built-in transaction script (also invoked with <code class="option">-b tpcb-like</code>)
issues seven commands per transaction over randomly chosen <code class="literal">aid</code>,
<code class="literal">tid</code>, <code class="literal">bid</code> and <code class="literal">delta</code>.
The scenario is inspired by the TPC-B benchmark, but is not actually TPC-B,
hence the name.
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p><code class="literal">BEGIN;</code></p></li><li class="listitem"><p><code class="literal">UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;</code></p></li><li class="listitem"><p><code class="literal">SELECT abalance FROM pgbench_accounts WHERE aid = :aid;</code></p></li><li class="listitem"><p><code class="literal">UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;</code></p></li><li class="listitem"><p><code class="literal">UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid;</code></p></li><li class="listitem"><p><code class="literal">INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta, CURRENT_TIMESTAMP);</code></p></li><li class="listitem"><p><code class="literal">END;</code></p></li></ol></div><p>
If you select the <code class="literal">simple-update</code> built-in (also <code class="option">-N</code>),
steps 4 and 5 aren't included in the transaction.
This will avoid update contention on these tables, but
it makes the test case even less like TPC-B.
</p><p>
If you select the <code class="literal">select-only</code> built-in (also <code class="option">-S</code>),
only the <code class="command">SELECT</code> is issued.
</p></div><div class="refsect2" id="id-1.9.4.11.9.3"><h3>Custom Scripts</h3><p>
<span class="application">pgbench</span> has support for running custom
benchmark scenarios by replacing the default transaction script
(described above) with a transaction script read from a file
(<code class="option">-f</code> option). In this case a <span class="quote">“<span class="quote">transaction</span>”</span>
counts as one execution of a script file.
</p><p>
A script file contains one or more SQL commands terminated by
semicolons. Empty lines and lines beginning with
<code class="literal">--</code> are ignored. Script files can also contain
<span class="quote">“<span class="quote">meta commands</span>”</span>, which are interpreted by <span class="application">pgbench</span>
itself, as described below.
</p><div class="note"><h3 class="title">Note</h3><p>
Before <span class="productname">PostgreSQL</span> 9.6, SQL commands in script files
were terminated by newlines, and so they could not be continued across
lines. Now a semicolon is <span class="emphasis"><em>required</em></span> to separate consecutive
SQL commands (though an SQL command does not need one if it is followed
by a meta command). If you need to create a script file that works with
both old and new versions of <span class="application">pgbench</span>, be sure to write
each SQL command on a single line ending with a semicolon.
</p><p>
It is assumed that pgbench scripts do not contain incomplete blocks of SQL
transactions. If at runtime the client reaches the end of the script without
completing the last transaction block, it will be aborted.
</p></div><p>
There is a simple variable-substitution facility for script files.
Variable names must consist of letters (including non-Latin letters),
digits, and underscores, with the first character not being a digit.
Variables can be set by the command-line <code class="option">-D</code> option,
explained above, or by the meta commands explained below.
In addition to any variables preset by <code class="option">-D</code> command-line options,
there are a few variables that are preset automatically, listed in
<a class="xref" href="pgbench.html#PGBENCH-AUTOMATIC-VARIABLES" title="Table 293. pgbench Automatic Variables">Table 293</a>. A value specified for these
variables using <code class="option">-D</code> takes precedence over the automatic presets.
Once set, a variable's
value can be inserted into an SQL command by writing
<code class="literal">:</code><em class="replaceable"><code>variablename</code></em>. When running more than
one client session, each session has its own set of variables.
<span class="application">pgbench</span> supports up to 255 variable uses in one
statement.
</p><div class="table" id="PGBENCH-AUTOMATIC-VARIABLES"><p class="title"><strong>Table 293. pgbench Automatic Variables</strong></p><div class="table-contents"><table class="table" summary="pgbench Automatic Variables" border="1"><colgroup><col class="col1" /><col class="col2" /></colgroup><thead><tr><th>Variable</th><th>Description</th></tr></thead><tbody><tr><td> <code class="literal">client_id</code> </td><td>unique number identifying the client session (starts from zero)</td></tr><tr><td> <code class="literal">default_seed</code> </td><td>seed used in hash and pseudorandom permutation functions by default</td></tr><tr><td> <code class="literal">random_seed</code> </td><td>random generator seed (unless overwritten with <code class="option">-D</code>)</td></tr><tr><td> <code class="literal">scale</code> </td><td>current scale factor</td></tr></tbody></table></div></div><br class="table-break" /><p>
Script file meta commands begin with a backslash (<code class="literal">\</code>) and
normally extend to the end of the line, although they can be continued
to additional lines by writing backslash-return.
Arguments to a meta command are separated by white space.
These meta commands are supported:
</p><div class="variablelist"><dl class="variablelist"><dt id="PGBENCH-METACOMMAND-GSET"><span class="term">
<code class="literal">\gset [<em class="replaceable"><code>prefix</code></em>]</code>
<code class="literal">\aset [<em class="replaceable"><code>prefix</code></em>]</code>
</span> <a href="#PGBENCH-METACOMMAND-GSET" class="id_link">#</a></dt><dd><p>
These commands may be used to end SQL queries, taking the place of the
terminating semicolon (<code class="literal">;</code>).
</p><p>
When the <code class="literal">\gset</code> command is used, the preceding SQL query is
expected to return one row, the columns of which are stored into variables
named after column names, and prefixed with <em class="replaceable"><code>prefix</code></em>
if provided.
</p><p>
When the <code class="literal">\aset</code> command is used, all combined SQL queries
(separated by <code class="literal">\;</code>) have their columns stored into variables
named after column names, and prefixed with <em class="replaceable"><code>prefix</code></em>
if provided. If a query returns no row, no assignment is made and the variable
can be tested for existence to detect this. If a query returns more than one
row, the last value is kept.
</p><p>
<code class="literal">\gset</code> and <code class="literal">\aset</code> cannot be used in
pipeline mode, since the query results are not yet available by the time
the commands would need them.
</p><p>
The following example puts the final account balance from the first query
into variable <em class="replaceable"><code>abalance</code></em>, and fills variables
<em class="replaceable"><code>p_two</code></em> and <em class="replaceable"><code>p_three</code></em>
with integers from the third query.
The result of the second query is discarded.
The result of the two last combined queries are stored in variables
<em class="replaceable"><code>four</code></em> and <em class="replaceable"><code>five</code></em>.
</p><pre class="programlisting">
UPDATE pgbench_accounts
SET abalance = abalance + :delta
WHERE aid = :aid
RETURNING abalance \gset
-- compound of two queries
SELECT 1 \;
SELECT 2 AS two, 3 AS three \gset p_
SELECT 4 AS four \; SELECT 5 AS five \aset
</pre></dd><dt id="PGBENCH-METACOMMAND-IF-ELSE"><span class="term"><code class="literal">\if</code> <em class="replaceable"><code>expression</code></em><br /></span><span class="term"><code class="literal">\elif</code> <em class="replaceable"><code>expression</code></em><br /></span><span class="term"><code class="literal">\else</code><br /></span><span class="term"><code class="literal">\endif</code></span> <a href="#PGBENCH-METACOMMAND-IF-ELSE" class="id_link">#</a></dt><dd><p>
This group of commands implements nestable conditional blocks,
similarly to <code class="literal">psql</code>'s <a class="xref" href="app-psql.html#PSQL-METACOMMAND-IF"><code class="literal">\if</code> <em class="replaceable"><code>expression</code></em></a>.
Conditional expressions are identical to those with <code class="literal">\set</code>,
with non-zero values interpreted as true.
</p></dd><dt id="PGBENCH-METACOMMAND-SET"><span class="term">
<code class="literal">\set <em class="replaceable"><code>varname</code></em> <em class="replaceable"><code>expression</code></em></code>
</span> <a href="#PGBENCH-METACOMMAND-SET" class="id_link">#</a></dt><dd><p>
Sets variable <em class="replaceable"><code>varname</code></em> to a value calculated
from <em class="replaceable"><code>expression</code></em>.
The expression may contain the <code class="literal">NULL</code> constant,
Boolean constants <code class="literal">TRUE</code> and <code class="literal">FALSE</code>,
integer constants such as <code class="literal">5432</code>,
double constants such as <code class="literal">3.14159</code>,
references to variables <code class="literal">:</code><em class="replaceable"><code>variablename</code></em>,
<a class="link" href="pgbench.html#PGBENCH-BUILTIN-OPERATORS" title="Built-in Operators">operators</a>
with their usual SQL precedence and associativity,
<a class="link" href="pgbench.html#PGBENCH-BUILTIN-FUNCTIONS" title="Built-In Functions">function calls</a>,
SQL <a class="link" href="functions-conditional.html#FUNCTIONS-CASE" title="9.18.1. CASE"><code class="token">CASE</code> generic conditional
expressions</a> and parentheses.
</p><p>
Functions and most operators return <code class="literal">NULL</code> on
<code class="literal">NULL</code> input.
</p><p>
For conditional purposes, non zero numerical values are
<code class="literal">TRUE</code>, zero numerical values and <code class="literal">NULL</code>
are <code class="literal">FALSE</code>.
</p><p>
Too large or small integer and double constants, as well as
integer arithmetic operators (<code class="literal">+</code>,
<code class="literal">-</code>, <code class="literal">*</code> and <code class="literal">/</code>)
raise errors on overflows.
</p><p>
When no final <code class="token">ELSE</code> clause is provided to a
<code class="token">CASE</code>, the default value is <code class="literal">NULL</code>.
</p><p>
Examples:
</p><pre class="programlisting">
\set ntellers 10 * :scale
\set aid (1021 * random(1, 100000 * :scale)) % \
(100000 * :scale) + 1
\set divx CASE WHEN :x <> 0 THEN :y/:x ELSE NULL END
</pre></dd><dt id="PGBENCH-METACOMMAND-SLEEP"><span class="term">
<code class="literal">\sleep <em class="replaceable"><code>number</code></em> [ us | ms | s ]</code>
</span> <a href="#PGBENCH-METACOMMAND-SLEEP" class="id_link">#</a></dt><dd><p>
Causes script execution to sleep for the specified duration in
microseconds (<code class="literal">us</code>), milliseconds (<code class="literal">ms</code>) or seconds
(<code class="literal">s</code>). If the unit is omitted then seconds are the default.
<em class="replaceable"><code>number</code></em> can be either an integer constant or a
<code class="literal">:</code><em class="replaceable"><code>variablename</code></em> reference to a variable
having an integer value.
</p><p>
Example:
</p><pre class="programlisting">
\sleep 10 ms
</pre></dd><dt id="PGBENCH-METACOMMAND-SETSHELL"><span class="term">
<code class="literal">\setshell <em class="replaceable"><code>varname</code></em> <em class="replaceable"><code>command</code></em> [ <em class="replaceable"><code>argument</code></em> ... ]</code>
</span> <a href="#PGBENCH-METACOMMAND-SETSHELL" class="id_link">#</a></dt><dd><p>
Sets variable <em class="replaceable"><code>varname</code></em> to the result of the shell command
<em class="replaceable"><code>command</code></em> with the given <em class="replaceable"><code>argument</code></em>(s).
The command must return an integer value through its standard output.
</p><p>
<em class="replaceable"><code>command</code></em> and each <em class="replaceable"><code>argument</code></em> can be either
a text constant or a <code class="literal">:</code><em class="replaceable"><code>variablename</code></em> reference
to a variable. If you want to use an <em class="replaceable"><code>argument</code></em> starting
with a colon, write an additional colon at the beginning of
<em class="replaceable"><code>argument</code></em>.
</p><p>
Example:
</p><pre class="programlisting">
\setshell variable_to_be_assigned command literal_argument :variable ::literal_starting_with_colon
</pre></dd><dt id="PGBENCH-METACOMMAND-SHELL"><span class="term">
<code class="literal">\shell <em class="replaceable"><code>command</code></em> [ <em class="replaceable"><code>argument</code></em> ... ]</code>
</span> <a href="#PGBENCH-METACOMMAND-SHELL" class="id_link">#</a></dt><dd><p>
Same as <code class="literal">\setshell</code>, but the result of the command
is discarded.
</p><p>
Example:
</p><pre class="programlisting">
\shell command literal_argument :variable ::literal_starting_with_colon
</pre></dd><dt id="PGBENCH-METACOMMAND-PIPELINE"><span class="term"><code class="literal">\startpipeline</code><br /></span><span class="term"><code class="literal">\endpipeline</code></span> <a href="#PGBENCH-METACOMMAND-PIPELINE" class="id_link">#</a></dt><dd><p>
These commands delimit the start and end of a pipeline of SQL
statements. In pipeline mode, statements are sent to the server
without waiting for the results of previous statements. See
<a class="xref" href="libpq-pipeline-mode.html" title="34.5. Pipeline Mode">Section 34.5</a> for more details.
Pipeline mode requires the use of extended query protocol.
</p></dd></dl></div></div><div class="refsect2" id="PGBENCH-BUILTIN-OPERATORS"><h3>Built-in Operators</h3><p>
The arithmetic, bitwise, comparison and logical operators listed in
<a class="xref" href="pgbench.html#PGBENCH-OPERATORS" title="Table 294. pgbench Operators">Table 294</a> are built into <span class="application">pgbench</span>
and may be used in expressions appearing in
<a class="link" href="pgbench.html#PGBENCH-METACOMMAND-SET"><code class="literal">\set</code></a>.
The operators are listed in increasing precedence order.
Except as noted, operators taking two numeric inputs will produce
a double value if either input is double, otherwise they produce
an integer result.
</p><div class="table" id="PGBENCH-OPERATORS"><p class="title"><strong>Table 294. pgbench Operators</strong></p><div class="table-contents"><table class="table" summary="pgbench Operators" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
Operator
</p>
<p>
Description
</p>
<p>
Example(s)
</p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>boolean</code></em> <code class="literal">OR</code> <em class="replaceable"><code>boolean</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>boolean</code></em></code>
</p>
<p>
Logical OR
</p>
<p>
<code class="literal">5 or 0</code>
→ <code class="returnvalue">TRUE</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>boolean</code></em> <code class="literal">AND</code> <em class="replaceable"><code>boolean</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>boolean</code></em></code>
</p>
<p>
Logical AND
</p>
<p>
<code class="literal">3 and 0</code>
→ <code class="returnvalue">FALSE</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="literal">NOT</code> <em class="replaceable"><code>boolean</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>boolean</code></em></code>
</p>
<p>
Logical NOT
</p>
<p>
<code class="literal">not false</code>
→ <code class="returnvalue">TRUE</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>boolean</code></em> <code class="literal">IS [NOT] (NULL|TRUE|FALSE)</code>
→ <code class="returnvalue"><em class="replaceable"><code>boolean</code></em></code>
</p>
<p>
Boolean value tests
</p>
<p>
<code class="literal">1 is null</code>
→ <code class="returnvalue">FALSE</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>value</code></em> <code class="literal">ISNULL|NOTNULL</code>
→ <code class="returnvalue"><em class="replaceable"><code>boolean</code></em></code>
</p>
<p>
Nullness tests
</p>
<p>
<code class="literal">1 notnull</code>
→ <code class="returnvalue">TRUE</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>number</code></em> <code class="literal">=</code> <em class="replaceable"><code>number</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>boolean</code></em></code>
</p>
<p>
Equal
</p>
<p>
<code class="literal">5 = 4</code>
→ <code class="returnvalue">FALSE</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>number</code></em> <code class="literal"><></code> <em class="replaceable"><code>number</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>boolean</code></em></code>
</p>
<p>
Not equal
</p>
<p>
<code class="literal">5 <> 4</code>
→ <code class="returnvalue">TRUE</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>number</code></em> <code class="literal">!=</code> <em class="replaceable"><code>number</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>boolean</code></em></code>
</p>
<p>
Not equal
</p>
<p>
<code class="literal">5 != 5</code>
→ <code class="returnvalue">FALSE</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>number</code></em> <code class="literal"><</code> <em class="replaceable"><code>number</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>boolean</code></em></code>
</p>
<p>
Less than
</p>
<p>
<code class="literal">5 < 4</code>
→ <code class="returnvalue">FALSE</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>number</code></em> <code class="literal"><=</code> <em class="replaceable"><code>number</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>boolean</code></em></code>
</p>
<p>
Less than or equal to
</p>
<p>
<code class="literal">5 <= 4</code>
→ <code class="returnvalue">FALSE</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>number</code></em> <code class="literal">></code> <em class="replaceable"><code>number</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>boolean</code></em></code>
</p>
<p>
Greater than
</p>
<p>
<code class="literal">5 > 4</code>
→ <code class="returnvalue">TRUE</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>number</code></em> <code class="literal">>=</code> <em class="replaceable"><code>number</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>boolean</code></em></code>
</p>
<p>
Greater than or equal to
</p>
<p>
<code class="literal">5 >= 4</code>
→ <code class="returnvalue">TRUE</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>integer</code></em> <code class="literal">|</code> <em class="replaceable"><code>integer</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>integer</code></em></code>
</p>
<p>
Bitwise OR
</p>
<p>
<code class="literal">1 | 2</code>
→ <code class="returnvalue">3</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>integer</code></em> <code class="literal">#</code> <em class="replaceable"><code>integer</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>integer</code></em></code>
</p>
<p>
Bitwise XOR
</p>
<p>
<code class="literal">1 # 3</code>
→ <code class="returnvalue">2</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>integer</code></em> <code class="literal">&</code> <em class="replaceable"><code>integer</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>integer</code></em></code>
</p>
<p>
Bitwise AND
</p>
<p>
<code class="literal">1 & 3</code>
→ <code class="returnvalue">1</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="literal">~</code> <em class="replaceable"><code>integer</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>integer</code></em></code>
</p>
<p>
Bitwise NOT
</p>
<p>
<code class="literal">~ 1</code>
→ <code class="returnvalue">-2</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>integer</code></em> <code class="literal"><<</code> <em class="replaceable"><code>integer</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>integer</code></em></code>
</p>
<p>
Bitwise shift left
</p>
<p>
<code class="literal">1 << 2</code>
→ <code class="returnvalue">4</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>integer</code></em> <code class="literal">>></code> <em class="replaceable"><code>integer</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>integer</code></em></code>
</p>
<p>
Bitwise shift right
</p>
<p>
<code class="literal">8 >> 2</code>
→ <code class="returnvalue">2</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>number</code></em> <code class="literal">+</code> <em class="replaceable"><code>number</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>number</code></em></code>
</p>
<p>
Addition
</p>
<p>
<code class="literal">5 + 4</code>
→ <code class="returnvalue">9</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>number</code></em> <code class="literal">-</code> <em class="replaceable"><code>number</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>number</code></em></code>
</p>
<p>
Subtraction
</p>
<p>
<code class="literal">3 - 2.0</code>
→ <code class="returnvalue">1.0</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>number</code></em> <code class="literal">*</code> <em class="replaceable"><code>number</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>number</code></em></code>
</p>
<p>
Multiplication
</p>
<p>
<code class="literal">5 * 4</code>
→ <code class="returnvalue">20</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>number</code></em> <code class="literal">/</code> <em class="replaceable"><code>number</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>number</code></em></code>
</p>
<p>
Division (truncates the result towards zero if both inputs are integers)
</p>
<p>
<code class="literal">5 / 3</code>
→ <code class="returnvalue">1</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<em class="replaceable"><code>integer</code></em> <code class="literal">%</code> <em class="replaceable"><code>integer</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>integer</code></em></code>
</p>
<p>
Modulo (remainder)
</p>
<p>
<code class="literal">3 % 2</code>
→ <code class="returnvalue">1</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="literal">-</code> <em class="replaceable"><code>number</code></em>
→ <code class="returnvalue"><em class="replaceable"><code>number</code></em></code>
</p>
<p>
Negation
</p>
<p>
<code class="literal">- 2.0</code>
→ <code class="returnvalue">-2.0</code>
</p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="refsect2" id="PGBENCH-BUILTIN-FUNCTIONS"><h3>Built-In Functions</h3><p>
The functions listed in <a class="xref" href="pgbench.html#PGBENCH-FUNCTIONS" title="Table 295. pgbench Functions">Table 295</a> are built
into <span class="application">pgbench</span> and may be used in expressions appearing in
<a class="link" href="pgbench.html#PGBENCH-METACOMMAND-SET"><code class="literal">\set</code></a>.
</p><div class="table" id="PGBENCH-FUNCTIONS"><p class="title"><strong>Table 295. pgbench Functions</strong></p><div class="table-contents"><table class="table" summary="pgbench Functions" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
Function
</p>
<p>
Description
</p>
<p>
Example(s)
</p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">abs</code> ( <em class="replaceable"><code>number</code></em> )
→ <code class="returnvalue"></code> same type as input
</p>
<p>
Absolute value
</p>
<p>
<code class="literal">abs(-17)</code>
→ <code class="returnvalue">17</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">debug</code> ( <em class="replaceable"><code>number</code></em> )
→ <code class="returnvalue"></code> same type as input
</p>
<p>
Prints the argument to <span class="systemitem">stderr</span>,
and returns the argument.
</p>
<p>
<code class="literal">debug(5432.1)</code>
→ <code class="returnvalue">5432.1</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">double</code> ( <em class="replaceable"><code>number</code></em> )
→ <code class="returnvalue">double</code>
</p>
<p>
Casts to double.
</p>
<p>
<code class="literal">double(5432)</code>
→ <code class="returnvalue">5432.0</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">exp</code> ( <em class="replaceable"><code>number</code></em> )
→ <code class="returnvalue">double</code>
</p>
<p>
Exponential (<code class="literal">e</code> raised to the given power)
</p>
<p>
<code class="literal">exp(1.0)</code>
→ <code class="returnvalue">2.718281828459045</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">greatest</code> ( <em class="replaceable"><code>number</code></em> [<span class="optional">, <code class="literal">...</code> </span>] )
→ <code class="returnvalue"></code> <code class="type">double</code> if any argument is double, else <code class="type">integer</code>
</p>
<p>
Selects the largest value among the arguments.
</p>
<p>
<code class="literal">greatest(5, 4, 3, 2)</code>
→ <code class="returnvalue">5</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">hash</code> ( <em class="parameter"><code>value</code></em> [<span class="optional">, <em class="parameter"><code>seed</code></em> </span>] )
→ <code class="returnvalue">integer</code>
</p>
<p>
This is an alias for <code class="function">hash_murmur2</code>.
</p>
<p>
<code class="literal">hash(10, 5432)</code>
→ <code class="returnvalue">-5817877081768721676</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">hash_fnv1a</code> ( <em class="parameter"><code>value</code></em> [<span class="optional">, <em class="parameter"><code>seed</code></em> </span>] )
→ <code class="returnvalue">integer</code>
</p>
<p>
Computes <a class="ulink" href="https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function" target="_top">FNV-1a hash</a>.
</p>
<p>
<code class="literal">hash_fnv1a(10, 5432)</code>
→ <code class="returnvalue">-7793829335365542153</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">hash_murmur2</code> ( <em class="parameter"><code>value</code></em> [<span class="optional">, <em class="parameter"><code>seed</code></em> </span>] )
→ <code class="returnvalue">integer</code>
</p>
<p>
Computes <a class="ulink" href="https://en.wikipedia.org/wiki/MurmurHash" target="_top">MurmurHash2 hash</a>.
</p>
<p>
<code class="literal">hash_murmur2(10, 5432)</code>
→ <code class="returnvalue">-5817877081768721676</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">int</code> ( <em class="replaceable"><code>number</code></em> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Casts to integer.
</p>
<p>
<code class="literal">int(5.4 + 3.8)</code>
→ <code class="returnvalue">9</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">least</code> ( <em class="replaceable"><code>number</code></em> [<span class="optional">, <code class="literal">...</code> </span>] )
→ <code class="returnvalue"></code> <code class="type">double</code> if any argument is double, else <code class="type">integer</code>
</p>
<p>
Selects the smallest value among the arguments.
</p>
<p>
<code class="literal">least(5, 4, 3, 2.1)</code>
→ <code class="returnvalue">2.1</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">ln</code> ( <em class="replaceable"><code>number</code></em> )
→ <code class="returnvalue">double</code>
</p>
<p>
Natural logarithm
</p>
<p>
<code class="literal">ln(2.718281828459045)</code>
→ <code class="returnvalue">1.0</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">mod</code> ( <em class="replaceable"><code>integer</code></em>, <em class="replaceable"><code>integer</code></em> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Modulo (remainder)
</p>
<p>
<code class="literal">mod(54, 32)</code>
→ <code class="returnvalue">22</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">permute</code> ( <em class="parameter"><code>i</code></em>, <em class="parameter"><code>size</code></em> [, <em class="parameter"><code>seed</code></em> ] )
→ <code class="returnvalue">integer</code>
</p>
<p>
Permuted value of <em class="parameter"><code>i</code></em>, in the range
<code class="literal">[0, size)</code>. This is the new position of
<em class="parameter"><code>i</code></em> (modulo <em class="parameter"><code>size</code></em>) in a
pseudorandom permutation of the integers <code class="literal">0...size-1</code>,
parameterized by <em class="parameter"><code>seed</code></em>, see below.
</p>
<p>
<code class="literal">permute(0, 4)</code>
→ <code class="returnvalue">an integer between 0 and 3</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">pi</code> ()
→ <code class="returnvalue">double</code>
</p>
<p>
Approximate value of <span class="symbol_font">π</span>
</p>
<p>
<code class="literal">pi()</code>
→ <code class="returnvalue">3.14159265358979323846</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">pow</code> ( <em class="parameter"><code>x</code></em>, <em class="parameter"><code>y</code></em> )
→ <code class="returnvalue">double</code>
</p>
<p class="func_signature">
<code class="function">power</code> ( <em class="parameter"><code>x</code></em>, <em class="parameter"><code>y</code></em> )
→ <code class="returnvalue">double</code>
</p>
<p>
<em class="parameter"><code>x</code></em> raised to the power of <em class="parameter"><code>y</code></em>
</p>
<p>
<code class="literal">pow(2.0, 10)</code>
→ <code class="returnvalue">1024.0</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">random</code> ( <em class="parameter"><code>lb</code></em>, <em class="parameter"><code>ub</code></em> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Computes a uniformly-distributed random integer in <code class="literal">[lb,
ub]</code>.
</p>
<p>
<code class="literal">random(1, 10)</code>
→ <code class="returnvalue">an integer between 1 and 10</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">random_exponential</code> ( <em class="parameter"><code>lb</code></em>, <em class="parameter"><code>ub</code></em>, <em class="parameter"><code>parameter</code></em> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Computes an exponentially-distributed random integer in <code class="literal">[lb,
ub]</code>, see below.
</p>
<p>
<code class="literal">random_exponential(1, 10, 3.0)</code>
→ <code class="returnvalue">an integer between 1 and 10</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">random_gaussian</code> ( <em class="parameter"><code>lb</code></em>, <em class="parameter"><code>ub</code></em>, <em class="parameter"><code>parameter</code></em> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Computes a Gaussian-distributed random integer in <code class="literal">[lb,
ub]</code>, see below.
</p>
<p>
<code class="literal">random_gaussian(1, 10, 2.5)</code>
→ <code class="returnvalue">an integer between 1 and 10</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">random_zipfian</code> ( <em class="parameter"><code>lb</code></em>, <em class="parameter"><code>ub</code></em>, <em class="parameter"><code>parameter</code></em> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Computes a Zipfian-distributed random integer in <code class="literal">[lb,
ub]</code>, see below.
</p>
<p>
<code class="literal">random_zipfian(1, 10, 1.5)</code>
→ <code class="returnvalue">an integer between 1 and 10</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">sqrt</code> ( <em class="replaceable"><code>number</code></em> )
→ <code class="returnvalue">double</code>
</p>
<p>
Square root
</p>
<p>
<code class="literal">sqrt(2.0)</code>
→ <code class="returnvalue">1.414213562</code>
</p></td></tr></tbody></table></div></div><br class="table-break" /><p>
The <code class="literal">random</code> function generates values using a uniform
distribution, that is all the values are drawn within the specified
range with equal probability. The <code class="literal">random_exponential</code>,
<code class="literal">random_gaussian</code> and <code class="literal">random_zipfian</code>
functions require an additional double parameter which determines the precise
shape of the distribution.
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
For an exponential distribution, <em class="replaceable"><code>parameter</code></em>
controls the distribution by truncating a quickly-decreasing
exponential distribution at <em class="replaceable"><code>parameter</code></em>, and then
projecting onto integers between the bounds.
To be precise, with
</p><div class="literallayout"><p><br />
f(x) = exp(-parameter * (x - min) / (max - min + 1)) / (1 - exp(-parameter))<br />
</p></div><p>
Then value <em class="replaceable"><code>i</code></em> between <em class="replaceable"><code>min</code></em> and
<em class="replaceable"><code>max</code></em> inclusive is drawn with probability:
<code class="literal">f(i) - f(i + 1)</code>.
</p><p>
Intuitively, the larger the <em class="replaceable"><code>parameter</code></em>, the more
frequently values close to <em class="replaceable"><code>min</code></em> are accessed, and the
less frequently values close to <em class="replaceable"><code>max</code></em> are accessed.
The closer to 0 <em class="replaceable"><code>parameter</code></em> is, the flatter (more
uniform) the access distribution.
A crude approximation of the distribution is that the most frequent 1%
values in the range, close to <em class="replaceable"><code>min</code></em>, are drawn
<em class="replaceable"><code>parameter</code></em>% of the time.
The <em class="replaceable"><code>parameter</code></em> value must be strictly positive.
</p></li><li class="listitem"><p>
For a Gaussian distribution, the interval is mapped onto a standard
normal distribution (the classical bell-shaped Gaussian curve) truncated
at <code class="literal">-parameter</code> on the left and <code class="literal">+parameter</code>
on the right.
Values in the middle of the interval are more likely to be drawn.
To be precise, if <code class="literal">PHI(x)</code> is the cumulative distribution
function of the standard normal distribution, with mean <code class="literal">mu</code>
defined as <code class="literal">(max + min) / 2.0</code>, with
</p><div class="literallayout"><p><br />
f(x) = PHI(2.0 * parameter * (x - mu) / (max - min + 1)) /<br />
(2.0 * PHI(parameter) - 1)<br />
</p></div><p>
then value <em class="replaceable"><code>i</code></em> between <em class="replaceable"><code>min</code></em> and
<em class="replaceable"><code>max</code></em> inclusive is drawn with probability:
<code class="literal">f(i + 0.5) - f(i - 0.5)</code>.
Intuitively, the larger the <em class="replaceable"><code>parameter</code></em>, the more
frequently values close to the middle of the interval are drawn, and the
less frequently values close to the <em class="replaceable"><code>min</code></em> and
<em class="replaceable"><code>max</code></em> bounds. About 67% of values are drawn from the
middle <code class="literal">1.0 / parameter</code>, that is a relative
<code class="literal">0.5 / parameter</code> around the mean, and 95% in the middle
<code class="literal">2.0 / parameter</code>, that is a relative
<code class="literal">1.0 / parameter</code> around the mean; for instance, if
<em class="replaceable"><code>parameter</code></em> is 4.0, 67% of values are drawn from the
middle quarter (1.0 / 4.0) of the interval (i.e., from
<code class="literal">3.0 / 8.0</code> to <code class="literal">5.0 / 8.0</code>) and 95% from
the middle half (<code class="literal">2.0 / 4.0</code>) of the interval (second and third
quartiles). The minimum allowed <em class="replaceable"><code>parameter</code></em>
value is 2.0.
</p></li><li class="listitem"><p>
<code class="literal">random_zipfian</code> generates a bounded Zipfian
distribution.
<em class="replaceable"><code>parameter</code></em> defines how skewed the distribution
is. The larger the <em class="replaceable"><code>parameter</code></em>, the more
frequently values closer to the beginning of the interval are drawn.
The distribution is such that, assuming the range starts from 1,
the ratio of the probability of drawing <em class="replaceable"><code>k</code></em>
versus drawing <em class="replaceable"><code>k+1</code></em> is
<code class="literal">((<em class="replaceable"><code>k</code></em>+1)/<em class="replaceable"><code>k</code></em>)**<em class="replaceable"><code>parameter</code></em></code>.
For example, <code class="literal">random_zipfian(1, ..., 2.5)</code> produces
the value <code class="literal">1</code> about <code class="literal">(2/1)**2.5 =
5.66</code> times more frequently than <code class="literal">2</code>, which
itself is produced <code class="literal">(3/2)**2.5 = 2.76</code> times more
frequently than <code class="literal">3</code>, and so on.
</p><p>
<span class="application">pgbench</span>'s implementation is based on
"Non-Uniform Random Variate Generation", Luc Devroye, p. 550-551,
Springer 1986. Due to limitations of that algorithm,
the <em class="replaceable"><code>parameter</code></em> value is restricted to
the range [1.001, 1000].
</p></li></ul></div><div class="note"><h3 class="title">Note</h3><p>
When designing a benchmark which selects rows non-uniformly, be aware
that the rows chosen may be correlated with other data such as IDs from
a sequence or the physical row ordering, which may skew performance
measurements.
</p><p>
To avoid this, you may wish to use the <code class="function">permute</code>
function, or some other additional step with similar effect, to shuffle
the selected rows and remove such correlations.
</p></div><p>
Hash functions <code class="literal">hash</code>, <code class="literal">hash_murmur2</code> and
<code class="literal">hash_fnv1a</code> accept an input value and an optional seed parameter.
In case the seed isn't provided the value of <code class="literal">:default_seed</code>
is used, which is initialized randomly unless set by the command-line
<code class="literal">-D</code> option.
</p><p>
<code class="literal">permute</code> accepts an input value, a size, and an optional
seed parameter. It generates a pseudorandom permutation of integers in
the range <code class="literal">[0, size)</code>, and returns the index of the input
value in the permuted values. The permutation chosen is parameterized by
the seed, which defaults to <code class="literal">:default_seed</code>, if not
specified. Unlike the hash functions, <code class="literal">permute</code> ensures
that there are no collisions or holes in the output values. Input values
outside the interval are interpreted modulo the size. The function raises
an error if the size is not positive. <code class="function">permute</code> can be
used to scatter the distribution of non-uniform random functions such as
<code class="literal">random_zipfian</code> or <code class="literal">random_exponential</code>
so that values drawn more often are not trivially correlated. For
instance, the following <span class="application">pgbench</span> script
simulates a possible real world workload typical for social media and
blogging platforms where a few accounts generate excessive load:
</p><pre class="programlisting">
\set size 1000000
\set r random_zipfian(1, :size, 1.07)
\set k 1 + permute(:r, :size)
</pre><p>
In some cases several distinct distributions are needed which don't correlate
with each other and this is when the optional seed parameter comes in handy:
</p><pre class="programlisting">
\set k1 1 + permute(:r, :size, :default_seed + 123)
\set k2 1 + permute(:r, :size, :default_seed + 321)
</pre><p>
A similar behavior can also be approximated with <code class="function">hash</code>:
</p><pre class="programlisting">
\set size 1000000
\set r random_zipfian(1, 100 * :size, 1.07)
\set k 1 + abs(hash(:r)) % :size
</pre><p>
However, since <code class="function">hash</code> generates collisions, some values
will not be reachable and others will be more frequent than expected from
the original distribution.
</p><p>
As an example, the full definition of the built-in TPC-B-like
transaction is:
</p><pre class="programlisting">
\set aid random(1, 100000 * :scale)
\set bid random(1, 1 * :scale)
\set tid random(1, 10 * :scale)
\set delta random(-5000, 5000)
BEGIN;
UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;
SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;
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);
END;
</pre><p>
This script allows each iteration of the transaction to reference
different, randomly-chosen rows. (This example also shows why it's
important for each client session to have its own variables —
otherwise they'd not be independently touching different rows.)
</p></div><div class="refsect2" id="id-1.9.4.11.9.6"><h3>Per-Transaction Logging</h3><p>
With the <code class="option">-l</code> option (but without
the <code class="option">--aggregate-interval</code> option),
<span class="application">pgbench</span> writes information about each transaction
to a log file. The log file will be named
<code class="filename"><em class="replaceable"><code>prefix</code></em>.<em class="replaceable"><code>nnn</code></em></code>,
where <em class="replaceable"><code>prefix</code></em> defaults to <code class="literal">pgbench_log</code>, and
<em class="replaceable"><code>nnn</code></em> is the PID of the
<span class="application">pgbench</span> process.
The prefix can be changed by using the <code class="option">--log-prefix</code> option.
If the <code class="option">-j</code> option is 2 or higher, so that there are multiple
worker threads, each will have its own log file. The first worker will
use 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
<code class="filename"><em class="replaceable"><code>prefix</code></em>.<em class="replaceable"><code>nnn</code></em>.<em class="replaceable"><code>mmm</code></em></code>,
where <em class="replaceable"><code>mmm</code></em> is a sequential number for each worker starting
with 1.
</p><p>
Each line in a log file describes one transaction.
It contains the following space-separated fields:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="replaceable"><code>client_id</code></em></span></dt><dd><p>
identifies the client session that ran the transaction
</p></dd><dt><span class="term"><em class="replaceable"><code>transaction_no</code></em></span></dt><dd><p>
counts how many transactions have been run by that session
</p></dd><dt><span class="term"><em class="replaceable"><code>time</code></em></span></dt><dd><p>
transaction's elapsed time, in microseconds
</p></dd><dt><span class="term"><em class="replaceable"><code>script_no</code></em></span></dt><dd><p>
identifies the script file that was used for the transaction
(useful when multiple scripts are specified
with <code class="option">-f</code> or <code class="option">-b</code>)
</p></dd><dt><span class="term"><em class="replaceable"><code>time_epoch</code></em></span></dt><dd><p>
transaction's completion time, as a Unix-epoch time stamp
</p></dd><dt><span class="term"><em class="replaceable"><code>time_us</code></em></span></dt><dd><p>
fractional-second part of transaction's completion time, in
microseconds
</p></dd><dt><span class="term"><em class="replaceable"><code>schedule_lag</code></em></span></dt><dd><p>
transaction start delay, that is the difference between the
transaction's scheduled start time and the time it actually
started, in microseconds
(present only if <code class="option">--rate</code> is specified)
</p></dd><dt><span class="term"><em class="replaceable"><code>retries</code></em></span></dt><dd><p>
count of retries after serialization or deadlock errors during the
transaction
(present only if <code class="option">--max-tries</code> is not equal to one)
</p></dd></dl></div><p>
</p><p>
When both <code class="option">--rate</code> and <code class="option">--latency-limit</code> are used,
the <em class="replaceable"><code>time</code></em> for a skipped transaction will be reported as
<code class="literal">skipped</code>.
If the transaction ends with a failure, its <em class="replaceable"><code>time</code></em>
will be reported as <code class="literal">failed</code>. If you use the
<code class="option">--failures-detailed</code> option, the
<em class="replaceable"><code>time</code></em> of the failed transaction will be reported as
<code class="literal">serialization</code> or
<code class="literal">deadlock</code> depending on the type of failure (see
<a class="xref" href="pgbench.html#FAILURES-AND-RETRIES" title="Failures and Serialization/Deadlock Retries">Failures and Serialization/Deadlock Retries</a> for more information).
</p><p>
Here is a snippet of a log file generated in a single-client run:
</p><pre class="screen">
0 199 2241 0 1175850568 995598
0 200 2465 0 1175850568 998079
0 201 2513 0 1175850569 608
0 202 2038 0 1175850569 2663
</pre><p>
Another example with <code class="literal">--rate=100</code>
and <code class="literal">--latency-limit=5</code> (note the additional
<em class="replaceable"><code>schedule_lag</code></em> column):
</p><pre class="screen">
0 81 4621 0 1412881037 912698 3005
0 82 6173 0 1412881037 914578 4304
0 83 skipped 0 1412881037 914578 5217
0 83 skipped 0 1412881037 914578 5099
0 83 4722 0 1412881037 916203 3108
0 84 4142 0 1412881037 918023 2333
0 85 2465 0 1412881037 919759 740
</pre><p>
In this example, transaction 82 was late, because its latency (6.173 ms) was
over the 5 ms limit. The next two transactions were skipped, because they
were already late before they were even started.
</p><p>
The following example shows a snippet of a log file with failures and
retries, with the maximum number of tries set to 10 (note the additional
<em class="replaceable"><code>retries</code></em> column):
</p><pre class="screen">
3 0 47423 0 1499414498 34501 3
3 1 8333 0 1499414498 42848 0
3 2 8358 0 1499414498 51219 0
4 0 72345 0 1499414498 59433 6
1 3 41718 0 1499414498 67879 4
1 4 8416 0 1499414498 76311 0
3 3 33235 0 1499414498 84469 3
0 0 failed 0 1499414498 84905 9
2 0 failed 0 1499414498 86248 9
3 4 8307 0 1499414498 92788 0
</pre><p>
</p><p>
If the <code class="option">--failures-detailed</code> option is used, the type of
failure is reported in the <em class="replaceable"><code>time</code></em> like this:
</p><pre class="screen">
3 0 47423 0 1499414498 34501 3
3 1 8333 0 1499414498 42848 0
3 2 8358 0 1499414498 51219 0
4 0 72345 0 1499414498 59433 6
1 3 41718 0 1499414498 67879 4
1 4 8416 0 1499414498 76311 0
3 3 33235 0 1499414498 84469 3
0 0 serialization 0 1499414498 84905 9
2 0 serialization 0 1499414498 86248 9
3 4 8307 0 1499414498 92788 0
</pre><p>
</p><p>
When running a long test on hardware that can handle a lot of transactions,
the log files can become very large. The <code class="option">--sampling-rate</code> option
can be used to log only a random sample of transactions.
</p></div><div class="refsect2" id="id-1.9.4.11.9.7"><h3>Aggregated Logging</h3><p>
With the <code class="option">--aggregate-interval</code> option, a different
format is used for the log files. Each log line describes one
aggregation interval. It contains the following space-separated
fields:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="replaceable"><code>interval_start</code></em></span></dt><dd><p>
start time of the interval, as a Unix-epoch time stamp
</p></dd><dt><span class="term"><em class="replaceable"><code>num_transactions</code></em></span></dt><dd><p>
number of transactions within the interval
</p></dd><dt><span class="term"><em class="replaceable"><code>sum_latency</code></em></span></dt><dd><p>
sum of transaction latencies
</p></dd><dt><span class="term"><em class="replaceable"><code>sum_latency_2</code></em></span></dt><dd><p>
sum of squares of transaction latencies
</p></dd><dt><span class="term"><em class="replaceable"><code>min_latency</code></em></span></dt><dd><p>
minimum transaction latency
</p></dd><dt><span class="term"><em class="replaceable"><code>max_latency</code></em></span></dt><dd><p>
maximum transaction latency
</p></dd><dt><span class="term"><em class="replaceable"><code>sum_lag</code></em></span></dt><dd><p>
sum of transaction start delays
(zero unless <code class="option">--rate</code> is specified)
</p></dd><dt><span class="term"><em class="replaceable"><code>sum_lag_2</code></em></span></dt><dd><p>
sum of squares of transaction start delays
(zero unless <code class="option">--rate</code> is specified)
</p></dd><dt><span class="term"><em class="replaceable"><code>min_lag</code></em></span></dt><dd><p>
minimum transaction start delay
(zero unless <code class="option">--rate</code> is specified)
</p></dd><dt><span class="term"><em class="replaceable"><code>max_lag</code></em></span></dt><dd><p>
maximum transaction start delay
(zero unless <code class="option">--rate</code> is specified)
</p></dd><dt><span class="term"><em class="replaceable"><code>skipped</code></em></span></dt><dd><p>
number of transactions skipped because they would have started too late
(zero unless <code class="option">--rate</code>
and <code class="option">--latency-limit</code> are specified)
</p></dd><dt><span class="term"><em class="replaceable"><code>retried</code></em></span></dt><dd><p>
number of retried transactions
(zero unless <code class="option">--max-tries</code> is not equal to one)
</p></dd><dt><span class="term"><em class="replaceable"><code>retries</code></em></span></dt><dd><p>
number of retries after serialization or deadlock errors
(zero unless <code class="option">--max-tries</code> is not equal to one)
</p></dd><dt><span class="term"><em class="replaceable"><code>serialization_failures</code></em></span></dt><dd><p>
number of transactions that got a serialization error and were not
retried afterwards
(zero unless <code class="option">--failures-detailed</code> is specified)
</p></dd><dt><span class="term"><em class="replaceable"><code>deadlock_failures</code></em></span></dt><dd><p>
number of transactions that got a deadlock error and were not
retried afterwards
(zero unless <code class="option">--failures-detailed</code> is specified)
</p></dd></dl></div><p>
</p><p>
Here is some example output generated with these options:
</p><pre class="screen">
<strong class="userinput"><code>pgbench --aggregate-interval=10 --time=20 --client=10 --log --rate=1000 --latency-limit=10 --failures-detailed --max-tries=10 test</code></strong>
1650260552 5178 26171317 177284491527 1136 44462 2647617 7321113867 0 9866 64 7564 28340 4148 0
1650260562 4808 25573984 220121792172 1171 62083 3037380 9666800914 0 9998 598 7392 26621 4527 0
</pre><p>
</p><p>
Notice that while the plain (unaggregated) log format shows which script
was used for each transaction, the aggregated format does not. Therefore if
you need per-script data, you need to aggregate the data on your own.
</p></div><div class="refsect2" id="id-1.9.4.11.9.8"><h3>Per-Statement Report</h3><p>
With the <code class="option">-r</code> option, <span class="application">pgbench</span>
collects the following statistics for each statement:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
<code class="literal">latency</code> — elapsed transaction time for each
statement. <span class="application">pgbench</span> reports an average value
of all successful runs of the statement.
</p></li><li class="listitem"><p>
The number of failures in this statement. See
<a class="xref" href="pgbench.html#FAILURES-AND-RETRIES" title="Failures and Serialization/Deadlock Retries">Failures and Serialization/Deadlock Retries</a> for more information.
</p></li><li class="listitem"><p>
The number of retries after a serialization or a deadlock error in this
statement. See <a class="xref" href="pgbench.html#FAILURES-AND-RETRIES" title="Failures and Serialization/Deadlock Retries">Failures and Serialization/Deadlock Retries</a> for more information.
</p></li></ul></div><p>
</p><p>
The report displays retry statistics only if the <code class="option">--max-tries</code>
option is not equal to 1.
</p><p>
All values are computed for each statement executed by every client and are
reported after the benchmark has finished.
</p><p>
For the default script, the output will look similar to this:
</p><pre class="screen">
starting vacuum...end.
transaction type: <builtin: TPC-B (sort of)>
scaling factor: 1
query mode: simple
number of clients: 10
number of threads: 1
maximum number of tries: 1
number of transactions per client: 1000
number of transactions actually processed: 10000/10000
number of failed transactions: 0 (0.000%)
number of transactions above the 50.0 ms latency limit: 1311/10000 (13.110 %)
latency average = 28.488 ms
latency stddev = 21.009 ms
initial connection time = 69.068 ms
tps = 346.224794 (without initial connection time)
statement latencies in milliseconds and failures:
0.012 0 \set aid random(1, 100000 * :scale)
0.002 0 \set bid random(1, 1 * :scale)
0.002 0 \set tid random(1, 10 * :scale)
0.002 0 \set delta random(-5000, 5000)
0.319 0 BEGIN;
0.834 0 UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;
0.641 0 SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
11.126 0 UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;
12.961 0 UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid;
0.634 0 INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta, CURRENT_TIMESTAMP);
1.957 0 END;
</pre><p>
Another example of output for the default script using serializable default
transaction isolation level (<code class="command">PGOPTIONS='-c
default_transaction_isolation=serializable' pgbench ...</code>):
</p><pre class="screen">
starting vacuum...end.
transaction type: <builtin: TPC-B (sort of)>
scaling factor: 1
query mode: simple
number of clients: 10
number of threads: 1
maximum number of tries: 10
number of transactions per client: 1000
number of transactions actually processed: 6317/10000
number of failed transactions: 3683 (36.830%)
number of transactions retried: 7667 (76.670%)
total number of retries: 45339
number of transactions above the 50.0 ms latency limit: 106/6317 (1.678 %)
latency average = 17.016 ms
latency stddev = 13.283 ms
initial connection time = 45.017 ms
tps = 186.792667 (without initial connection time)
statement latencies in milliseconds, failures and retries:
0.006 0 0 \set aid random(1, 100000 * :scale)
0.001 0 0 \set bid random(1, 1 * :scale)
0.001 0 0 \set tid random(1, 10 * :scale)
0.001 0 0 \set delta random(-5000, 5000)
0.385 0 0 BEGIN;
0.773 0 1 UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;
0.624 0 0 SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
1.098 320 3762 UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;
0.582 3363 41576 UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid;
0.465 0 0 INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta, CURRENT_TIMESTAMP);
1.933 0 0 END;
</pre><p>
If multiple script files are specified, all statistics are reported
separately for each script file.
</p><p>
Note that collecting the additional timing information needed for
per-statement latency computation adds some overhead. This will slow
average execution speed and lower the computed TPS. The amount
of slowdown varies significantly depending on platform and hardware.
Comparing average TPS values with and without latency reporting enabled
is a good way to measure if the timing overhead is significant.
</p></div><div class="refsect2" id="FAILURES-AND-RETRIES"><h3>Failures and Serialization/Deadlock Retries</h3><p>
When executing <span class="application">pgbench</span>, there are three main types
of errors:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
Errors of the main program. They are the most serious and always result
in an immediate exit from <span class="application">pgbench</span> with the
corresponding error message. They include:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>
errors at the beginning of <span class="application">pgbench</span>
(e.g. an invalid option value);
</p></li><li class="listitem"><p>
errors in the initialization mode (e.g. the query to create
tables for built-in scripts fails);
</p></li><li class="listitem"><p>
errors before starting threads (e.g. could not connect to the
database server, syntax error in the meta command, thread
creation failure);
</p></li><li class="listitem"><p>
internal <span class="application">pgbench</span> errors (which are
supposed to never occur...).
</p></li></ul></div></li><li class="listitem"><p>
Errors when the thread manages its clients (e.g. the client could not
start a connection to the database server / the socket for connecting
the client to the database server has become invalid). In such cases
all clients of this thread stop while other threads continue to work.
</p></li><li class="listitem"><p>
Direct client errors. They lead to immediate exit from
<span class="application">pgbench</span> with the corresponding error message
only in the case of an internal <span class="application">pgbench</span>
error (which are supposed to never occur...). Otherwise in the worst
case they only lead to the abortion of the failed client while other
clients continue their run (but some client errors are handled without
an abortion of the client and reported separately, see below). Later in
this section it is assumed that the discussed errors are only the
direct client errors and they are not internal
<span class="application">pgbench</span> errors.
</p></li></ul></div><p>
</p><p>
A client's run is aborted in case of a serious error; for example, the
connection with the database server was lost or the end of script was reached
without completing the last transaction. In addition, if execution of an SQL
or meta command fails for reasons other than serialization or deadlock errors,
the client is aborted. Otherwise, if an SQL command fails with serialization or
deadlock errors, the client is not aborted. In such cases, the current
transaction is rolled back, which also includes setting the client variables
as they were before the run of this transaction (it is assumed that one
transaction script contains only one transaction; see
<a class="xref" href="pgbench.html#TRANSACTIONS-AND-SCRIPTS" title="What Is the “Transaction” Actually Performed in pgbench?">What Is the "Transaction" Actually Performed in pgbench?</a> for more information).
Transactions with serialization or deadlock errors are repeated after
rollbacks until they complete successfully or reach the maximum
number of tries (specified by the <code class="option">--max-tries</code> option) / the maximum
time of retries (specified by the <code class="option">--latency-limit</code> option) / the end
of benchmark (specified by the <code class="option">--time</code> option). If
the last trial run fails, this transaction will be reported as failed but
the client is not aborted and continues to work.
</p><div class="note"><h3 class="title">Note</h3><p>
Without specifying the <code class="option">--max-tries</code> option, a transaction will
never be retried after a serialization or deadlock error because its default
value is 1. Use an unlimited number of tries (<code class="literal">--max-tries=0</code>)
and the <code class="option">--latency-limit</code> option to limit only the maximum time
of tries. You can also use the <code class="option">--time</code> option to limit the
benchmark duration under an unlimited number of tries.
</p><p>
Be careful when repeating scripts that contain multiple transactions: the
script is always retried completely, so successful transactions can be
performed several times.
</p><p>
Be careful when repeating transactions with shell commands. Unlike the
results of SQL commands, the results of shell commands are not rolled back,
except for the variable value of the <code class="command">\setshell</code> command.
</p></div><p>
The latency of a successful transaction includes the entire time of
transaction execution with rollbacks and retries. The latency is measured
only for successful transactions and commands but not for failed transactions
or commands.
</p><p>
The main report contains the number of failed transactions. If the
<code class="option">--max-tries</code> option is not equal to 1, the main report also
contains statistics related to retries: the total number of retried
transactions and total number of retries. The per-script report inherits all
these fields from the main report. The per-statement report displays retry
statistics only if the <code class="option">--max-tries</code> option is not equal to 1.
</p><p>
If you want to group failures by basic types in per-transaction and
aggregation logs, as well as in the main and per-script reports, use the
<code class="option">--failures-detailed</code> option. If you also want to distinguish
all errors and failures (errors without retrying) by type including which
limit for retries was exceeded and how much it was exceeded by for the
serialization/deadlock failures, use the <code class="option">--verbose-errors</code>
option.
</p></div><div class="refsect2" id="id-1.9.4.11.9.10"><h3>Table Access Methods</h3><p>
You may specify the <a class="link" href="tableam.html" title="Chapter 63. Table Access Method Interface Definition">Table Access Method</a>
for the pgbench tables. The environment variable <code class="envar">PGOPTIONS</code>
specifies database configuration options that are passed to PostgreSQL via
the command line (See <a class="xref" href="config-setting.html#CONFIG-SETTING-SHELL" title="20.1.4. Parameter Interaction via the Shell">Section 20.1.4</a>).
For example, a hypothetical default Table Access Method for the tables that
pgbench creates called <code class="literal">wuzza</code> can be specified with:
</p><pre class="programlisting">
PGOPTIONS='-c default_table_access_method=wuzza'
</pre><p>
</p></div><div class="refsect2" id="id-1.9.4.11.9.11"><h3>Good Practices</h3><p>
It is very easy to use <span class="application">pgbench</span> to produce completely
meaningless numbers. Here are some guidelines to help you get useful
results.
</p><p>
In the first place, <span class="emphasis"><em>never</em></span> believe any test that runs
for only a few seconds. Use the <code class="option">-t</code> or <code class="option">-T</code> option
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.
It's a good idea to try the test run a few times, to find out if your
numbers are reproducible or not.
</p><p>
For the default TPC-B-like test scenario, the initialization scale factor
(<code class="option">-s</code>) should be at least as large as the largest number of
clients you intend to test (<code class="option">-c</code>); else you'll mostly be
measuring update contention. There are only <code class="option">-s</code> rows in
the <code class="structname">pgbench_branches</code> table, and every transaction wants to
update one of them, so <code class="option">-c</code> values in excess of <code class="option">-s</code>
will undoubtedly result in lots of transactions blocked waiting for
other transactions.
</p><p>
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
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
autovacuum is enabled it can result in unpredictable changes in measured
performance.
</p><p>
A limitation of <span class="application">pgbench</span> is that it can itself become
the bottleneck when trying to test a large number of client sessions.
This can be alleviated by running <span class="application">pgbench</span> on a different
machine from the database server, although low network latency will be
essential. It might even be useful to run several <span class="application">pgbench</span>
instances concurrently, on several client machines, against the same
database server.
</p></div><div class="refsect2" id="id-1.9.4.11.9.12"><h3>Security</h3><p>
If untrusted users have access to a database that has not adopted a
<a class="link" href="ddl-schemas.html#DDL-SCHEMAS-PATTERNS" title="5.9.6. Usage Patterns">secure schema usage pattern</a>,
do not run <span class="application">pgbench</span> in that
database. <span class="application">pgbench</span> uses unqualified names and
does not manipulate the search path.
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