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diff --git a/doc/src/sgml/ref/pgbench.sgml b/doc/src/sgml/ref/pgbench.sgml new file mode 100644 index 0000000..7d66679 --- /dev/null +++ b/doc/src/sgml/ref/pgbench.sgml @@ -0,0 +1,2950 @@ +<!-- +doc/src/sgml/ref/pgbench.sgml +PostgreSQL documentation +--> + +<refentry id="pgbench"> + <indexterm zone="pgbench"> + <primary>pgbench</primary> + </indexterm> + + <refmeta> + <refentrytitle><application>pgbench</application></refentrytitle> + <manvolnum>1</manvolnum> + <refmiscinfo>Application</refmiscinfo> + </refmeta> + + <refnamediv> + <refname>pgbench</refname> + <refpurpose>run a benchmark test on <productname>PostgreSQL</productname></refpurpose> + </refnamediv> + + <refsynopsisdiv> + <cmdsynopsis> + <command>pgbench</command> + <arg choice="plain"><option>-i</option></arg> + <arg rep="repeat"><replaceable>option</replaceable></arg> + <arg choice="opt"><replaceable>dbname</replaceable></arg> + </cmdsynopsis> + <cmdsynopsis> + <command>pgbench</command> + <arg rep="repeat"><replaceable>option</replaceable></arg> + <arg choice="opt"><replaceable>dbname</replaceable></arg> + </cmdsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + <para> + <application>pgbench</application> is a simple program for running benchmark + tests on <productname>PostgreSQL</productname>. 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, <application>pgbench</application> tests a scenario that is + loosely based on TPC-B, involving five <command>SELECT</command>, + <command>UPDATE</command>, and <command>INSERT</command> commands per transaction. + However, it is easy to test other cases by writing your own transaction + script files. + </para> + + <para> + Typical output from <application>pgbench</application> looks like: + +<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) +</screen> + + 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 <xref linkend="failures-and-retries"/> + 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 + <option>-T</option> 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 <xref linkend="failures-and-retries"/> + for more information). + The last line reports the number of transactions per second. + </para> + + <para> + The default TPC-B-like transaction test requires specific tables to be + set up beforehand. <application>pgbench</application> should be invoked with + the <option>-i</option> (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: + +<programlisting> +pgbench -i <optional> <replaceable>other-options</replaceable> </optional> <replaceable>dbname</replaceable> +</programlisting> + + where <replaceable>dbname</replaceable> is the name of the already-created + database to test in. (You may also need <option>-h</option>, + <option>-p</option>, and/or <option>-U</option> options to specify how to + connect to the database server.) + </para> + + <caution> + <para> + <literal>pgbench -i</literal> creates four tables <structname>pgbench_accounts</structname>, + <structname>pgbench_branches</structname>, <structname>pgbench_history</structname>, and + <structname>pgbench_tellers</structname>, + destroying any existing tables of these names. + Be very careful to use another database if you have tables having these + names! + </para> + </caution> + + <para> + At the default <quote>scale factor</quote> of 1, the tables initially + contain this many rows: +<screen> +table # of rows +--------------------------------- +pgbench_branches 1 +pgbench_tellers 10 +pgbench_accounts 100000 +pgbench_history 0 +</screen> + You can (and, for most purposes, probably should) increase the number + of rows by using the <option>-s</option> (scale factor) option. The + <option>-F</option> (fillfactor) option might also be used at this point. + </para> + + <para> + Once you have done the necessary setup, you can run your benchmark + with a command that doesn't include <option>-i</option>, that is + +<programlisting> +pgbench <optional> <replaceable>options</replaceable> </optional> <replaceable>dbname</replaceable> +</programlisting> + + In nearly all cases, you'll need some options to make a useful test. + The most important options are <option>-c</option> (number of clients), + <option>-t</option> (number of transactions), <option>-T</option> (time limit), + and <option>-f</option> (specify a custom script file). + See below for a full list. + </para> + </refsect1> + + <refsect1> + <title>Options</title> + + <para> + 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. + </para> + + <refsect2 id="pgbench-init-options"> + <title>Initialization Options</title> + + <para> + <application>pgbench</application> accepts the following command-line + initialization arguments: + + <variablelist> + + <varlistentry> + <term><replaceable class="parameter">dbname</replaceable></term> + <listitem> + <para> + Specifies the name of the database to test in. If this is + not specified, the environment variable + <envar>PGDATABASE</envar> is used. If that is not set, the + user name specified for the connection is used. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-i</option></term> + <term><option>--initialize</option></term> + <listitem> + <para> + Required to invoke initialization mode. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-I <replaceable>init_steps</replaceable></option></term> + <term><option>--init-steps=<replaceable>init_steps</replaceable></option></term> + <listitem> + <para> + Perform just a selected set of the normal initialization steps. + <replaceable>init_steps</replaceable> specifies the + initialization steps to be performed, using one character per step. + Each step is invoked in the specified order. + The default is <literal>dtgvp</literal>. + The available steps are: + + <variablelist> + <varlistentry> + <term><literal>d</literal> (Drop)</term> + <listitem> + <para> + Drop any existing <application>pgbench</application> tables. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>t</literal> (create Tables)</term> + <listitem> + <para> + Create the tables used by the + standard <application>pgbench</application> scenario, namely + <structname>pgbench_accounts</structname>, + <structname>pgbench_branches</structname>, + <structname>pgbench_history</structname>, and + <structname>pgbench_tellers</structname>. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>g</literal> or <literal>G</literal> (Generate data, client-side or server-side)</term> + <listitem> + <para> + Generate data and load it into the standard tables, + replacing any data already present. + </para> + <para> + With <literal>g</literal> (client-side data generation), + data is generated in <command>pgbench</command> client and then + sent to the server. This uses the client/server bandwidth + extensively through a <command>COPY</command>. + <command>pgbench</command> uses the FREEZE option with version 14 or later + of <productname>PostgreSQL</productname> to speed up + subsequent <command>VACUUM</command>, unless partitions are enabled. + Using <literal>g</literal> causes logging to print one message + every 100,000 rows while generating data for the + <structname>pgbench_accounts</structname> table. + </para> + <para> + With <literal>G</literal> (server-side data generation), + only small queries are sent from the <command>pgbench</command> + 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 <literal>G</literal> causes logging not to print any progress + message while generating data. + </para> + <para> + The default initialization behavior uses client-side data + generation (equivalent to <literal>g</literal>). + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>v</literal> (Vacuum)</term> + <listitem> + <para> + Invoke <command>VACUUM</command> on the standard tables. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>p</literal> (create Primary keys)</term> + <listitem> + <para> + Create primary key indexes on the standard tables. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term><literal>f</literal> (create Foreign keys)</term> + <listitem> + <para> + Create foreign key constraints between the standard tables. + (Note that this step is not performed by default.) + </para> + </listitem> + </varlistentry> + </variablelist></para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-F</option> <replaceable>fillfactor</replaceable></term> + <term><option>--fillfactor=</option><replaceable>fillfactor</replaceable></term> + <listitem> + <para> + Create the <structname>pgbench_accounts</structname>, + <structname>pgbench_tellers</structname> and + <structname>pgbench_branches</structname> tables with the given fillfactor. + Default is 100. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-n</option></term> + <term><option>--no-vacuum</option></term> + <listitem> + <para> + Perform no vacuuming during initialization. + (This option suppresses the <literal>v</literal> initialization step, + even if it was specified in <option>-I</option>.) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-q</option></term> + <term><option>--quiet</option></term> + <listitem> + <para> + 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). + </para> + <para> + This setting has no effect if <literal>G</literal> is specified + in <option>-I</option>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-s</option> <replaceable>scale_factor</replaceable></term> + <term><option>--scale=</option><replaceable>scale_factor</replaceable></term> + <listitem> + <para> + Multiply the number of rows generated by the scale factor. + For example, <literal>-s 100</literal> will create 10,000,000 rows + in the <structname>pgbench_accounts</structname> table. Default is 1. + When the scale is 20,000 or larger, the columns used to + hold account identifiers (<structfield>aid</structfield> columns) + will switch to using larger integers (<type>bigint</type>), + in order to be big enough to hold the range of account + identifiers. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--foreign-keys</option></term> + <listitem> + <para> + Create foreign key constraints between the standard tables. + (This option adds the <literal>f</literal> step to the initialization + step sequence, if it is not already present.) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--index-tablespace=<replaceable>index_tablespace</replaceable></option></term> + <listitem> + <para> + Create indexes in the specified tablespace, rather than the default + tablespace. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--partition-method=<replaceable>NAME</replaceable></option></term> + <listitem> + <para> + Create a partitioned <literal>pgbench_accounts</literal> table with + <replaceable>NAME</replaceable> method. + Expected values are <literal>range</literal> or <literal>hash</literal>. + This option requires that <option>--partitions</option> is set to non-zero. + If unspecified, default is <literal>range</literal>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--partitions=<replaceable>NUM</replaceable></option></term> + <listitem> + <para> + Create a partitioned <literal>pgbench_accounts</literal> table with + <replaceable>NUM</replaceable> partitions of nearly equal size for + the scaled number of accounts. + Default is <literal>0</literal>, meaning no partitioning. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--tablespace=<replaceable>tablespace</replaceable></option></term> + <listitem> + <para> + Create tables in the specified tablespace, rather than the default + tablespace. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--unlogged-tables</option></term> + <listitem> + <para> + Create all tables as unlogged tables, rather than permanent tables. + </para> + </listitem> + </varlistentry> + + </variablelist> + </para> + + </refsect2> + + <refsect2 id="pgbench-run-options"> + <title>Benchmarking Options</title> + + <para> + <application>pgbench</application> accepts the following command-line + benchmarking arguments: + + <variablelist> + <varlistentry> + <term><option>-b</option> <replaceable>scriptname[@weight]</replaceable></term> + <term><option>--builtin</option>=<replaceable>scriptname[@weight]</replaceable></term> + <listitem> + <para> + Add the specified built-in script to the list of scripts to be executed. + Available built-in scripts are: <literal>tpcb-like</literal>, + <literal>simple-update</literal> and <literal>select-only</literal>. + Unambiguous prefixes of built-in names are accepted. + With the special name <literal>list</literal>, show the list of built-in scripts + and exit immediately. + </para> + <para> + Optionally, write an integer weight after <literal>@</literal> to + adjust the probability of selecting this script versus other ones. + The default weight is 1. + See below for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-c</option> <replaceable>clients</replaceable></term> + <term><option>--client=</option><replaceable>clients</replaceable></term> + <listitem> + <para> + Number of clients simulated, that is, number of concurrent database + sessions. Default is 1. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-C</option></term> + <term><option>--connect</option></term> + <listitem> + <para> + Establish a new connection for each transaction, rather than + doing it just once per client session. + This is useful to measure the connection overhead. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-d</option></term> + <term><option>--debug</option></term> + <listitem> + <para> + Print debugging output. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-D</option> <replaceable>varname</replaceable><literal>=</literal><replaceable>value</replaceable></term> + <term><option>--define=</option><replaceable>varname</replaceable><literal>=</literal><replaceable>value</replaceable></term> + <listitem> + <para> + Define a variable for use by a custom script (see below). + Multiple <option>-D</option> options are allowed. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-f</option> <replaceable>filename[@weight]</replaceable></term> + <term><option>--file=</option><replaceable>filename[@weight]</replaceable></term> + <listitem> + <para> + Add a transaction script read from <replaceable>filename</replaceable> + to the list of scripts to be executed. + </para> + <para> + Optionally, write an integer weight after <literal>@</literal> 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 <literal>@</literal> + character, append a weight so that there is no ambiguity, for + example <literal>filen@me@1</literal>.) + See below for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-j</option> <replaceable>threads</replaceable></term> + <term><option>--jobs=</option><replaceable>threads</replaceable></term> + <listitem> + <para> + Number of worker threads within <application>pgbench</application>. + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-l</option></term> + <term><option>--log</option></term> + <listitem> + <para> + Write information about each transaction to a log file. + See below for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-L</option> <replaceable>limit</replaceable></term> + <term><option>--latency-limit=</option><replaceable>limit</replaceable></term> + <listitem> + <para> + Transactions that last more than <replaceable>limit</replaceable> milliseconds + are counted and reported separately, as <firstterm>late</firstterm>. + </para> + <para> + When throttling is used (<option>--rate=...</option>), transactions that + lag behind schedule by more than <replaceable>limit</replaceable> 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 + <firstterm>skipped</firstterm>. + </para> + <para> + When the <option>--max-tries</option> 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 + <replaceable>limit</replaceable> ms. To limit only the time of tries + and not their number, use <literal>--max-tries=0</literal>. By + default, the option <option>--max-tries</option> is set to 1 and + transactions with serialization/deadlock errors are not retried. See + <xref linkend="failures-and-retries"/> for more information about + retrying such transactions. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-M</option> <replaceable>querymode</replaceable></term> + <term><option>--protocol=</option><replaceable>querymode</replaceable></term> + <listitem> + <para> + Protocol to use for submitting queries to the server: + <itemizedlist> + <listitem> + <para><literal>simple</literal>: use simple query protocol.</para> + </listitem> + <listitem> + <para><literal>extended</literal>: use extended query protocol.</para> + </listitem> + <listitem> + <para><literal>prepared</literal>: use extended query protocol with prepared statements.</para> + </listitem> + </itemizedlist> + + In the <literal>prepared</literal> mode, <application>pgbench</application> + reuses the parse analysis result starting from the second query + iteration, so <application>pgbench</application> runs faster + than in other modes. + </para> + <para> + The default is simple query protocol. (See <xref linkend="protocol"/> + for more information.) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-n</option></term> + <term><option>--no-vacuum</option></term> + <listitem> + <para> + Perform no vacuuming before running the test. + This option is <emphasis>necessary</emphasis> + if you are running a custom test scenario that does not include + the standard tables <structname>pgbench_accounts</structname>, + <structname>pgbench_branches</structname>, <structname>pgbench_history</structname>, and + <structname>pgbench_tellers</structname>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-N</option></term> + <term><option>--skip-some-updates</option></term> + <listitem> + <para> + Run built-in simple-update script. + Shorthand for <option>-b simple-update</option>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-P</option> <replaceable>sec</replaceable></term> + <term><option>--progress=</option><replaceable>sec</replaceable></term> + <listitem> + <para> + Show progress report every <replaceable>sec</replaceable> 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 (<option>-R</option>), 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 <option>--max-tries</option> is used to enable transaction retries + after serialization/deadlock errors, the report includes the number of + retried transactions and the sum of all retries. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-r</option></term> + <term><option>--report-per-command</option></term> + <listitem> + <para> + 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 + <option>--max-tries</option> option is not equal to 1. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-R</option> <replaceable>rate</replaceable></term> + <term><option>--rate=</option><replaceable>rate</replaceable></term> + <listitem> + <para> + 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. + </para> + <para> + 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. + </para> + <para> + 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. + </para> + + <para> + If <option>--latency-limit</option> is used together with <option>--rate</option>, + 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. + </para> + + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-s</option> <replaceable>scale_factor</replaceable></term> + <term><option>--scale=</option><replaceable>scale_factor</replaceable></term> + <listitem> + <para> + Report the specified scale factor in <application>pgbench</application>'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 <structname>pgbench_branches</structname> table. + However, when testing only custom benchmarks (<option>-f</option> option), + the scale factor will be reported as 1 unless this option is used. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-S</option></term> + <term><option>--select-only</option></term> + <listitem> + <para> + Run built-in select-only script. + Shorthand for <option>-b select-only</option>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-t</option> <replaceable>transactions</replaceable></term> + <term><option>--transactions=</option><replaceable>transactions</replaceable></term> + <listitem> + <para> + Number of transactions each client runs. Default is 10. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-T</option> <replaceable>seconds</replaceable></term> + <term><option>--time=</option><replaceable>seconds</replaceable></term> + <listitem> + <para> + Run the test for this many seconds, rather than a fixed number of + transactions per client. <option>-t</option> and + <option>-T</option> are mutually exclusive. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-v</option></term> + <term><option>--vacuum-all</option></term> + <listitem> + <para> + Vacuum all four standard tables before running the test. + With neither <option>-n</option> nor <option>-v</option>, <application>pgbench</application> will vacuum the + <structname>pgbench_tellers</structname> and <structname>pgbench_branches</structname> + tables, and will truncate <structname>pgbench_history</structname>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--aggregate-interval=<replaceable>seconds</replaceable></option></term> + <listitem> + <para> + Length of aggregation interval (in seconds). May be used only + with <option>-l</option> option. With this option, the log contains + per-interval summary data, as described below. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--failures-detailed</option></term> + <listitem> + <para> + Report failures in per-transaction and aggregation logs, as well as in + the main and per-script reports, grouped by the following types: + <itemizedlist> + <listitem> + <para>serialization failures;</para> + </listitem> + <listitem> + <para>deadlock failures;</para> + </listitem> + </itemizedlist> + See <xref linkend="failures-and-retries"/> for more information. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--log-prefix=<replaceable>prefix</replaceable></option></term> + <listitem> + <para> + Set the filename prefix for the log files created by + <option>--log</option>. The default is <literal>pgbench_log</literal>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--max-tries=<replaceable>number_of_tries</replaceable></option></term> + <listitem> + <para> + Enable retries for transactions with serialization/deadlock errors and + set the maximum number of these tries. This option can be combined with + the <option>--latency-limit</option> option which limits the total time + of all transaction tries; moreover, you cannot use an unlimited number + of tries (<literal>--max-tries=0</literal>) without + <option>--latency-limit</option> or <option>--time</option>. + The default value is 1 and transactions with serialization/deadlock + errors are not retried. See <xref linkend="failures-and-retries"/> + for more information about retrying such transactions. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--progress-timestamp</option></term> + <listitem> + <para> + When showing progress (option <option>-P</option>), 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--random-seed=</option><replaceable>seed</replaceable></term> + <listitem> + <para> + 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 <replaceable>seed</replaceable> may be: + <literal>time</literal> (the default, the seed is based on the current time), + <literal>rand</literal> (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 + (<literal>random...</literal> functions) or implicitly (for instance option + <option>--rate</option> uses it to schedule transactions). + When explicitly set, the value used for seeding is shown on the terminal. + Any value allowed for <replaceable>seed</replaceable> may also be + provided through the environment variable + <literal>PGBENCH_RANDOM_SEED</literal>. + To ensure that the provided seed impacts all possible uses, put this option + first or use the environment variable. + </para> + <para> + Setting the seed explicitly allows to reproduce a <command>pgbench</command> + run exactly, as far as random numbers are concerned. + As the random state is managed per thread, this means the exact same + <command>pgbench</command> 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--sampling-rate=<replaceable>rate</replaceable></option></term> + <listitem> + <para> + 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. + </para> + <para> + 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). + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--show-script=</option><replaceable>scriptname</replaceable></term> + <listitem> + <para> + Show the actual code of builtin script <replaceable>scriptname</replaceable> + on stderr, and exit immediately. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--verbose-errors</option></term> + <listitem> + <para> + 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 <xref linkend="failures-and-retries"/> for more information. + </para> + </listitem> + </varlistentry> + + </variablelist> + </para> + + </refsect2> + + <refsect2 id="pgbench-common-options"> + <title>Common Options</title> + + <para> + <application>pgbench</application> also accepts the following common command-line + arguments for connection parameters: + + <variablelist> + + <varlistentry> + <term><option>-h</option> <replaceable>hostname</replaceable></term> + <term><option>--host=</option><replaceable>hostname</replaceable></term> + <listitem> + <para> + The database server's host name + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-p</option> <replaceable>port</replaceable></term> + <term><option>--port=</option><replaceable>port</replaceable></term> + <listitem> + <para> + The database server's port number + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-U</option> <replaceable>login</replaceable></term> + <term><option>--username=</option><replaceable>login</replaceable></term> + <listitem> + <para> + The user name to connect as + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-V</option></term> + <term><option>--version</option></term> + <listitem> + <para> + Print the <application>pgbench</application> version and exit. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-?</option></term> + <term><option>--help</option></term> + <listitem> + <para> + Show help about <application>pgbench</application> command line + arguments, and exit. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + </refsect2> + </refsect1> + + <refsect1> + <title>Exit Status</title> + + <para> + 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, + <application>pgbench</application> will print partial results. + </para> + </refsect1> + + <refsect1> + <title>Environment</title> + + <variablelist> + <varlistentry> + <term><envar>PGDATABASE</envar></term> + <term><envar>PGHOST</envar></term> + <term><envar>PGPORT</envar></term> + <term><envar>PGUSER</envar></term> + + <listitem> + <para> + Default connection parameters. + </para> + </listitem> + </varlistentry> + </variablelist> + + <para> + This utility, like most other <productname>PostgreSQL</productname> utilities, + uses the environment variables supported by <application>libpq</application> + (see <xref linkend="libpq-envars"/>). + </para> + + <para> + The environment variable <envar>PG_COLOR</envar> specifies whether to use + color in diagnostic messages. Possible values are + <literal>always</literal>, <literal>auto</literal> and + <literal>never</literal>. + </para> + </refsect1> + + <refsect1> + <title>Notes</title> + + <refsect2 id="transactions-and-scripts" xreflabel="What Is the "Transaction" Actually Performed in pgbench?"> + <title>What Is the <quote>Transaction</quote> Actually Performed in <application>pgbench</application>?</title> + + <para> + <application>pgbench</application> executes test scripts chosen randomly + from a specified list. + The scripts may include built-in scripts specified with <option>-b</option> + and user-provided scripts specified with <option>-f</option>. + Each script may be given a relative weight specified after an + <literal>@</literal> so as to change its selection probability. + The default weight is <literal>1</literal>. + Scripts with a weight of <literal>0</literal> are ignored. + </para> + + <para> + The default built-in transaction script (also invoked with <option>-b tpcb-like</option>) + issues seven commands per transaction over randomly chosen <literal>aid</literal>, + <literal>tid</literal>, <literal>bid</literal> and <literal>delta</literal>. + The scenario is inspired by the TPC-B benchmark, but is not actually TPC-B, + hence the name. + </para> + + <orderedlist> + <listitem><para><literal>BEGIN;</literal></para></listitem> + <listitem><para><literal>UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;</literal></para></listitem> + <listitem><para><literal>SELECT abalance FROM pgbench_accounts WHERE aid = :aid;</literal></para></listitem> + <listitem><para><literal>UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;</literal></para></listitem> + <listitem><para><literal>UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid;</literal></para></listitem> + <listitem><para><literal>INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta, CURRENT_TIMESTAMP);</literal></para></listitem> + <listitem><para><literal>END;</literal></para></listitem> + </orderedlist> + + <para> + If you select the <literal>simple-update</literal> built-in (also <option>-N</option>), + 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. + </para> + + <para> + If you select the <literal>select-only</literal> built-in (also <option>-S</option>), + only the <command>SELECT</command> is issued. + </para> + </refsect2> + + <refsect2> + <title>Custom Scripts</title> + + <para> + <application>pgbench</application> has support for running custom + benchmark scenarios by replacing the default transaction script + (described above) with a transaction script read from a file + (<option>-f</option> option). In this case a <quote>transaction</quote> + counts as one execution of a script file. + </para> + + <para> + A script file contains one or more SQL commands terminated by + semicolons. Empty lines and lines beginning with + <literal>--</literal> are ignored. Script files can also contain + <quote>meta commands</quote>, which are interpreted by <application>pgbench</application> + itself, as described below. + </para> + + <note> + <para> + Before <productname>PostgreSQL</productname> 9.6, SQL commands in script files + were terminated by newlines, and so they could not be continued across + lines. Now a semicolon is <emphasis>required</emphasis> 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 <application>pgbench</application>, be sure to write + each SQL command on a single line ending with a semicolon. + </para> + <para> + 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. + </para> + </note> + + <para> + 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 <option>-D</option> option, + explained above, or by the meta commands explained below. + In addition to any variables preset by <option>-D</option> command-line options, + there are a few variables that are preset automatically, listed in + <xref linkend="pgbench-automatic-variables"/>. A value specified for these + variables using <option>-D</option> takes precedence over the automatic presets. + Once set, a variable's + value can be inserted into an SQL command by writing + <literal>:</literal><replaceable>variablename</replaceable>. When running more than + one client session, each session has its own set of variables. + <application>pgbench</application> supports up to 255 variable uses in one + statement. + </para> + + <table id="pgbench-automatic-variables"> + <title>pgbench Automatic Variables</title> + <tgroup cols="2"> + <colspec colname="col1" colwidth="1*"/> + <colspec colname="col2" colwidth="2*"/> + <thead> + <row> + <entry>Variable</entry> + <entry>Description</entry> + </row> + </thead> + + <tbody> + <row> + <entry> <literal>client_id</literal> </entry> + <entry>unique number identifying the client session (starts from zero)</entry> + </row> + + <row> + <entry> <literal>default_seed</literal> </entry> + <entry>seed used in hash and pseudorandom permutation functions by default</entry> + </row> + + <row> + <entry> <literal>random_seed</literal> </entry> + <entry>random generator seed (unless overwritten with <option>-D</option>)</entry> + </row> + + <row> + <entry> <literal>scale</literal> </entry> + <entry>current scale factor</entry> + </row> + </tbody> + </tgroup> + </table> + + <para> + Script file meta commands begin with a backslash (<literal>\</literal>) 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: + </para> + + <variablelist> + <varlistentry id='pgbench-metacommand-gset'> + <term> + <literal>\gset [<replaceable>prefix</replaceable>]</literal> + <literal>\aset [<replaceable>prefix</replaceable>]</literal> + </term> + + <listitem> + <para> + These commands may be used to end SQL queries, taking the place of the + terminating semicolon (<literal>;</literal>). + </para> + + <para> + When the <literal>\gset</literal> 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 <replaceable>prefix</replaceable> + if provided. + </para> + + <para> + When the <literal>\aset</literal> command is used, all combined SQL queries + (separated by <literal>\;</literal>) have their columns stored into variables + named after column names, and prefixed with <replaceable>prefix</replaceable> + 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. + </para> + + <para> + <literal>\gset</literal> and <literal>\aset</literal> cannot be used in + pipeline mode, since the query results are not yet available by the time + the commands would need them. + </para> + + <para> + The following example puts the final account balance from the first query + into variable <replaceable>abalance</replaceable>, and fills variables + <replaceable>p_two</replaceable> and <replaceable>p_three</replaceable> + 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 + <replaceable>four</replaceable> and <replaceable>five</replaceable>. +<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 +</programlisting></para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>\if</literal> <replaceable class="parameter">expression</replaceable></term> + <term><literal>\elif</literal> <replaceable class="parameter">expression</replaceable></term> + <term><literal>\else</literal></term> + <term><literal>\endif</literal></term> + <listitem> + <para> + This group of commands implements nestable conditional blocks, + similarly to <literal>psql</literal>'s <xref linkend="psql-metacommand-if"/>. + Conditional expressions are identical to those with <literal>\set</literal>, + with non-zero values interpreted as true. + </para> + </listitem> + </varlistentry> + + <varlistentry id='pgbench-metacommand-set'> + <term> + <literal>\set <replaceable>varname</replaceable> <replaceable>expression</replaceable></literal> + </term> + + <listitem> + <para> + Sets variable <replaceable>varname</replaceable> to a value calculated + from <replaceable>expression</replaceable>. + The expression may contain the <literal>NULL</literal> constant, + Boolean constants <literal>TRUE</literal> and <literal>FALSE</literal>, + integer constants such as <literal>5432</literal>, + double constants such as <literal>3.14159</literal>, + references to variables <literal>:</literal><replaceable>variablename</replaceable>, + <link linkend="pgbench-builtin-operators">operators</link> + with their usual SQL precedence and associativity, + <link linkend="pgbench-builtin-functions">function calls</link>, + SQL <link linkend="functions-case"><token>CASE</token> generic conditional + expressions</link> and parentheses. + </para> + + <para> + Functions and most operators return <literal>NULL</literal> on + <literal>NULL</literal> input. + </para> + + <para> + For conditional purposes, non zero numerical values are + <literal>TRUE</literal>, zero numerical values and <literal>NULL</literal> + are <literal>FALSE</literal>. + </para> + + <para> + Too large or small integer and double constants, as well as + integer arithmetic operators (<literal>+</literal>, + <literal>-</literal>, <literal>*</literal> and <literal>/</literal>) + raise errors on overflows. + </para> + + <para> + When no final <token>ELSE</token> clause is provided to a + <token>CASE</token>, the default value is <literal>NULL</literal>. + </para> + + <para> + Examples: +<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 +</programlisting></para> + </listitem> + </varlistentry> + + <varlistentry> + <term> + <literal>\sleep <replaceable>number</replaceable> [ us | ms | s ]</literal> + </term> + + <listitem> + <para> + Causes script execution to sleep for the specified duration in + microseconds (<literal>us</literal>), milliseconds (<literal>ms</literal>) or seconds + (<literal>s</literal>). If the unit is omitted then seconds are the default. + <replaceable>number</replaceable> can be either an integer constant or a + <literal>:</literal><replaceable>variablename</replaceable> reference to a variable + having an integer value. + </para> + + <para> + Example: +<programlisting> +\sleep 10 ms +</programlisting></para> + </listitem> + </varlistentry> + + <varlistentry> + <term> + <literal>\setshell <replaceable>varname</replaceable> <replaceable>command</replaceable> [ <replaceable>argument</replaceable> ... ]</literal> + </term> + + <listitem> + <para> + Sets variable <replaceable>varname</replaceable> to the result of the shell command + <replaceable>command</replaceable> with the given <replaceable>argument</replaceable>(s). + The command must return an integer value through its standard output. + </para> + + <para> + <replaceable>command</replaceable> and each <replaceable>argument</replaceable> can be either + a text constant or a <literal>:</literal><replaceable>variablename</replaceable> reference + to a variable. If you want to use an <replaceable>argument</replaceable> starting + with a colon, write an additional colon at the beginning of + <replaceable>argument</replaceable>. + </para> + + <para> + Example: +<programlisting> +\setshell variable_to_be_assigned command literal_argument :variable ::literal_starting_with_colon +</programlisting></para> + </listitem> + </varlistentry> + + <varlistentry> + <term> + <literal>\shell <replaceable>command</replaceable> [ <replaceable>argument</replaceable> ... ]</literal> + </term> + + <listitem> + <para> + Same as <literal>\setshell</literal>, but the result of the command + is discarded. + </para> + + <para> + Example: +<programlisting> +\shell command literal_argument :variable ::literal_starting_with_colon +</programlisting></para> + </listitem> + </varlistentry> + + <varlistentry id='pgbench-metacommand-pipeline'> + <term><literal>\startpipeline</literal></term> + <term><literal>\endpipeline</literal></term> + + <listitem> + <para> + 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 + <xref linkend="libpq-pipeline-mode"/> for more details. + Pipeline mode requires the use of extended query protocol. + </para> + </listitem> + </varlistentry> + + </variablelist> + </refsect2> + + <refsect2 id="pgbench-builtin-operators"> + <title>Built-in Operators</title> + + <para> + The arithmetic, bitwise, comparison and logical operators listed in + <xref linkend="pgbench-operators"/> are built into <application>pgbench</application> + and may be used in expressions appearing in + <link linkend="pgbench-metacommand-set"><literal>\set</literal></link>. + 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. + </para> + + <table id="pgbench-operators"> + <title>pgbench Operators</title> + <tgroup cols="1"> + <thead> + <row> + <entry role="func_table_entry"><para role="func_signature"> + Operator + </para> + <para> + Description + </para> + <para> + Example(s) + </para></entry> + </row> + </thead> + + <tbody> + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>boolean</replaceable> <literal>OR</literal> <replaceable>boolean</replaceable> + <returnvalue><replaceable>boolean</replaceable></returnvalue> + </para> + <para> + Logical OR + </para> + <para> + <literal>5 or 0</literal> + <returnvalue>TRUE</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>boolean</replaceable> <literal>AND</literal> <replaceable>boolean</replaceable> + <returnvalue><replaceable>boolean</replaceable></returnvalue> + </para> + <para> + Logical AND + </para> + <para> + <literal>3 and 0</literal> + <returnvalue>FALSE</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <literal>NOT</literal> <replaceable>boolean</replaceable> + <returnvalue><replaceable>boolean</replaceable></returnvalue> + </para> + <para> + Logical NOT + </para> + <para> + <literal>not false</literal> + <returnvalue>TRUE</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>boolean</replaceable> <literal>IS [NOT] (NULL|TRUE|FALSE)</literal> + <returnvalue><replaceable>boolean</replaceable></returnvalue> + </para> + <para> + Boolean value tests + </para> + <para> + <literal>1 is null</literal> + <returnvalue>FALSE</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>value</replaceable> <literal>ISNULL|NOTNULL</literal> + <returnvalue><replaceable>boolean</replaceable></returnvalue> + </para> + <para> + Nullness tests + </para> + <para> + <literal>1 notnull</literal> + <returnvalue>TRUE</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>number</replaceable> <literal>=</literal> <replaceable>number</replaceable> + <returnvalue><replaceable>boolean</replaceable></returnvalue> + </para> + <para> + Equal + </para> + <para> + <literal>5 = 4</literal> + <returnvalue>FALSE</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>number</replaceable> <literal><></literal> <replaceable>number</replaceable> + <returnvalue><replaceable>boolean</replaceable></returnvalue> + </para> + <para> + Not equal + </para> + <para> + <literal>5 <> 4</literal> + <returnvalue>TRUE</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>number</replaceable> <literal>!=</literal> <replaceable>number</replaceable> + <returnvalue><replaceable>boolean</replaceable></returnvalue> + </para> + <para> + Not equal + </para> + <para> + <literal>5 != 5</literal> + <returnvalue>FALSE</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>number</replaceable> <literal><</literal> <replaceable>number</replaceable> + <returnvalue><replaceable>boolean</replaceable></returnvalue> + </para> + <para> + Less than + </para> + <para> + <literal>5 < 4</literal> + <returnvalue>FALSE</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>number</replaceable> <literal><=</literal> <replaceable>number</replaceable> + <returnvalue><replaceable>boolean</replaceable></returnvalue> + </para> + <para> + Less than or equal to + </para> + <para> + <literal>5 <= 4</literal> + <returnvalue>FALSE</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>number</replaceable> <literal>></literal> <replaceable>number</replaceable> + <returnvalue><replaceable>boolean</replaceable></returnvalue> + </para> + <para> + Greater than + </para> + <para> + <literal>5 > 4</literal> + <returnvalue>TRUE</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>number</replaceable> <literal>>=</literal> <replaceable>number</replaceable> + <returnvalue><replaceable>boolean</replaceable></returnvalue> + </para> + <para> + Greater than or equal to + </para> + <para> + <literal>5 >= 4</literal> + <returnvalue>TRUE</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>integer</replaceable> <literal>|</literal> <replaceable>integer</replaceable> + <returnvalue><replaceable>integer</replaceable></returnvalue> + </para> + <para> + Bitwise OR + </para> + <para> + <literal>1 | 2</literal> + <returnvalue>3</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>integer</replaceable> <literal>#</literal> <replaceable>integer</replaceable> + <returnvalue><replaceable>integer</replaceable></returnvalue> + </para> + <para> + Bitwise XOR + </para> + <para> + <literal>1 # 3</literal> + <returnvalue>2</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>integer</replaceable> <literal>&</literal> <replaceable>integer</replaceable> + <returnvalue><replaceable>integer</replaceable></returnvalue> + </para> + <para> + Bitwise AND + </para> + <para> + <literal>1 & 3</literal> + <returnvalue>1</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <literal>~</literal> <replaceable>integer</replaceable> + <returnvalue><replaceable>integer</replaceable></returnvalue> + </para> + <para> + Bitwise NOT + </para> + <para> + <literal>~ 1</literal> + <returnvalue>-2</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>integer</replaceable> <literal><<</literal> <replaceable>integer</replaceable> + <returnvalue><replaceable>integer</replaceable></returnvalue> + </para> + <para> + Bitwise shift left + </para> + <para> + <literal>1 << 2</literal> + <returnvalue>4</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>integer</replaceable> <literal>>></literal> <replaceable>integer</replaceable> + <returnvalue><replaceable>integer</replaceable></returnvalue> + </para> + <para> + Bitwise shift right + </para> + <para> + <literal>8 >> 2</literal> + <returnvalue>2</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>number</replaceable> <literal>+</literal> <replaceable>number</replaceable> + <returnvalue><replaceable>number</replaceable></returnvalue> + </para> + <para> + Addition + </para> + <para> + <literal>5 + 4</literal> + <returnvalue>9</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>number</replaceable> <literal>-</literal> <replaceable>number</replaceable> + <returnvalue><replaceable>number</replaceable></returnvalue> + </para> + <para> + Subtraction + </para> + <para> + <literal>3 - 2.0</literal> + <returnvalue>1.0</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>number</replaceable> <literal>*</literal> <replaceable>number</replaceable> + <returnvalue><replaceable>number</replaceable></returnvalue> + </para> + <para> + Multiplication + </para> + <para> + <literal>5 * 4</literal> + <returnvalue>20</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>number</replaceable> <literal>/</literal> <replaceable>number</replaceable> + <returnvalue><replaceable>number</replaceable></returnvalue> + </para> + <para> + Division (truncates the result towards zero if both inputs are integers) + </para> + <para> + <literal>5 / 3</literal> + <returnvalue>1</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <replaceable>integer</replaceable> <literal>%</literal> <replaceable>integer</replaceable> + <returnvalue><replaceable>integer</replaceable></returnvalue> + </para> + <para> + Modulo (remainder) + </para> + <para> + <literal>3 % 2</literal> + <returnvalue>1</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <literal>-</literal> <replaceable>number</replaceable> + <returnvalue><replaceable>number</replaceable></returnvalue> + </para> + <para> + Negation + </para> + <para> + <literal>- 2.0</literal> + <returnvalue>-2.0</returnvalue> + </para></entry> + </row> + </tbody> + </tgroup> + </table> + </refsect2> + + <refsect2 id="pgbench-builtin-functions"> + <title>Built-In Functions</title> + + <para> + The functions listed in <xref linkend="pgbench-functions"/> are built + into <application>pgbench</application> and may be used in expressions appearing in + <link linkend="pgbench-metacommand-set"><literal>\set</literal></link>. + </para> + + <!-- list pgbench functions in alphabetical order --> + <table id="pgbench-functions"> + <title>pgbench Functions</title> + <tgroup cols="1"> + <thead> + <row> + <entry role="func_table_entry"><para role="func_signature"> + Function + </para> + <para> + Description + </para> + <para> + Example(s) + </para></entry> + </row> + </thead> + + <tbody> + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>abs</function> ( <replaceable>number</replaceable> ) + <returnvalue></returnvalue> same type as input + </para> + <para> + Absolute value + </para> + <para> + <literal>abs(-17)</literal> + <returnvalue>17</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>debug</function> ( <replaceable>number</replaceable> ) + <returnvalue></returnvalue> same type as input + </para> + <para> + Prints the argument to <systemitem>stderr</systemitem>, + and returns the argument. + </para> + <para> + <literal>debug(5432.1)</literal> + <returnvalue>5432.1</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>double</function> ( <replaceable>number</replaceable> ) + <returnvalue>double</returnvalue> + </para> + <para> + Casts to double. + </para> + <para> + <literal>double(5432)</literal> + <returnvalue>5432.0</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>exp</function> ( <replaceable>number</replaceable> ) + <returnvalue>double</returnvalue> + </para> + <para> + Exponential (<literal>e</literal> raised to the given power) + </para> + <para> + <literal>exp(1.0)</literal> + <returnvalue>2.718281828459045</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>greatest</function> ( <replaceable>number</replaceable> <optional>, <literal>...</literal> </optional> ) + <returnvalue></returnvalue> <type>double</type> if any argument is double, else <type>integer</type> + </para> + <para> + Selects the largest value among the arguments. + </para> + <para> + <literal>greatest(5, 4, 3, 2)</literal> + <returnvalue>5</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>hash</function> ( <parameter>value</parameter> <optional>, <parameter>seed</parameter> </optional> ) + <returnvalue>integer</returnvalue> + </para> + <para> + This is an alias for <function>hash_murmur2</function>. + </para> + <para> + <literal>hash(10, 5432)</literal> + <returnvalue>-5817877081768721676</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>hash_fnv1a</function> ( <parameter>value</parameter> <optional>, <parameter>seed</parameter> </optional> ) + <returnvalue>integer</returnvalue> + </para> + <para> + Computes <ulink url="https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function">FNV-1a hash</ulink>. + </para> + <para> + <literal>hash_fnv1a(10, 5432)</literal> + <returnvalue>-7793829335365542153</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>hash_murmur2</function> ( <parameter>value</parameter> <optional>, <parameter>seed</parameter> </optional> ) + <returnvalue>integer</returnvalue> + </para> + <para> + Computes <ulink url="https://en.wikipedia.org/wiki/MurmurHash">MurmurHash2 hash</ulink>. + </para> + <para> + <literal>hash_murmur2(10, 5432)</literal> + <returnvalue>-5817877081768721676</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>int</function> ( <replaceable>number</replaceable> ) + <returnvalue>integer</returnvalue> + </para> + <para> + Casts to integer. + </para> + <para> + <literal>int(5.4 + 3.8)</literal> + <returnvalue>9</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>least</function> ( <replaceable>number</replaceable> <optional>, <literal>...</literal> </optional> ) + <returnvalue></returnvalue> <type>double</type> if any argument is double, else <type>integer</type> + </para> + <para> + Selects the smallest value among the arguments. + </para> + <para> + <literal>least(5, 4, 3, 2.1)</literal> + <returnvalue>2.1</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>ln</function> ( <replaceable>number</replaceable> ) + <returnvalue>double</returnvalue> + </para> + <para> + Natural logarithm + </para> + <para> + <literal>ln(2.718281828459045)</literal> + <returnvalue>1.0</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> +<function>mod</function> ( <replaceable>integer</replaceable>, <replaceable>integer</replaceable> ) + <returnvalue>integer</returnvalue> + </para> + <para> + Modulo (remainder) + </para> + <para> + <literal>mod(54, 32)</literal> + <returnvalue>22</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>permute</function> ( <parameter>i</parameter>, <parameter>size</parameter> [, <parameter>seed</parameter> ] ) + <returnvalue>integer</returnvalue> + </para> + <para> + Permuted value of <parameter>i</parameter>, in the range + <literal>[0, size)</literal>. This is the new position of + <parameter>i</parameter> (modulo <parameter>size</parameter>) in a + pseudorandom permutation of the integers <literal>0...size-1</literal>, + parameterized by <parameter>seed</parameter>, see below. + </para> + <para> + <literal>permute(0, 4)</literal> + <returnvalue>an integer between 0 and 3</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>pi</function> () + <returnvalue>double</returnvalue> + </para> + <para> + Approximate value of <phrase role="symbol_font">π</phrase> + </para> + <para> + <literal>pi()</literal> + <returnvalue>3.14159265358979323846</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>pow</function> ( <parameter>x</parameter>, <parameter>y</parameter> ) + <returnvalue>double</returnvalue> + </para> + <para role="func_signature"> + <function>power</function> ( <parameter>x</parameter>, <parameter>y</parameter> ) + <returnvalue>double</returnvalue> + </para> + <para> + <parameter>x</parameter> raised to the power of <parameter>y</parameter> + </para> + <para> + <literal>pow(2.0, 10)</literal> + <returnvalue>1024.0</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>random</function> ( <parameter>lb</parameter>, <parameter>ub</parameter> ) + <returnvalue>integer</returnvalue> + </para> + <para> + Computes a uniformly-distributed random integer in <literal>[lb, + ub]</literal>. + </para> + <para> + <literal>random(1, 10)</literal> + <returnvalue>an integer between 1 and 10</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>random_exponential</function> ( <parameter>lb</parameter>, <parameter>ub</parameter>, <parameter>parameter</parameter> ) + <returnvalue>integer</returnvalue> + </para> + <para> + Computes an exponentially-distributed random integer in <literal>[lb, + ub]</literal>, see below. + </para> + <para> + <literal>random_exponential(1, 10, 3.0)</literal> + <returnvalue>an integer between 1 and 10</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>random_gaussian</function> ( <parameter>lb</parameter>, <parameter>ub</parameter>, <parameter>parameter</parameter> ) + <returnvalue>integer</returnvalue> + </para> + <para> + Computes a Gaussian-distributed random integer in <literal>[lb, + ub]</literal>, see below. + </para> + <para> + <literal>random_gaussian(1, 10, 2.5)</literal> + <returnvalue>an integer between 1 and 10</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>random_zipfian</function> ( <parameter>lb</parameter>, <parameter>ub</parameter>, <parameter>parameter</parameter> ) + <returnvalue>integer</returnvalue> + </para> + <para> + Computes a Zipfian-distributed random integer in <literal>[lb, + ub]</literal>, see below. + </para> + <para> + <literal>random_zipfian(1, 10, 1.5)</literal> + <returnvalue>an integer between 1 and 10</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <function>sqrt</function> ( <replaceable>number</replaceable> ) + <returnvalue>double</returnvalue> + </para> + <para> + Square root + </para> + <para> + <literal>sqrt(2.0)</literal> + <returnvalue>1.414213562</returnvalue> + </para></entry> + </row> + </tbody> + </tgroup> + </table> + + <para> + The <literal>random</literal> function generates values using a uniform + distribution, that is all the values are drawn within the specified + range with equal probability. The <literal>random_exponential</literal>, + <literal>random_gaussian</literal> and <literal>random_zipfian</literal> + functions require an additional double parameter which determines the precise + shape of the distribution. + </para> + + <itemizedlist> + <listitem> + <para> + For an exponential distribution, <replaceable>parameter</replaceable> + controls the distribution by truncating a quickly-decreasing + exponential distribution at <replaceable>parameter</replaceable>, and then + projecting onto integers between the bounds. + To be precise, with +<literallayout> +f(x) = exp(-parameter * (x - min) / (max - min + 1)) / (1 - exp(-parameter)) +</literallayout> + Then value <replaceable>i</replaceable> between <replaceable>min</replaceable> and + <replaceable>max</replaceable> inclusive is drawn with probability: + <literal>f(i) - f(i + 1)</literal>. + </para> + + <para> + Intuitively, the larger the <replaceable>parameter</replaceable>, the more + frequently values close to <replaceable>min</replaceable> are accessed, and the + less frequently values close to <replaceable>max</replaceable> are accessed. + The closer to 0 <replaceable>parameter</replaceable> 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 <replaceable>min</replaceable>, are drawn + <replaceable>parameter</replaceable>% of the time. + The <replaceable>parameter</replaceable> value must be strictly positive. + </para> + </listitem> + + <listitem> + <para> + For a Gaussian distribution, the interval is mapped onto a standard + normal distribution (the classical bell-shaped Gaussian curve) truncated + at <literal>-parameter</literal> on the left and <literal>+parameter</literal> + on the right. + Values in the middle of the interval are more likely to be drawn. + To be precise, if <literal>PHI(x)</literal> is the cumulative distribution + function of the standard normal distribution, with mean <literal>mu</literal> + defined as <literal>(max + min) / 2.0</literal>, with +<literallayout> +f(x) = PHI(2.0 * parameter * (x - mu) / (max - min + 1)) / + (2.0 * PHI(parameter) - 1) +</literallayout> + then value <replaceable>i</replaceable> between <replaceable>min</replaceable> and + <replaceable>max</replaceable> inclusive is drawn with probability: + <literal>f(i + 0.5) - f(i - 0.5)</literal>. + Intuitively, the larger the <replaceable>parameter</replaceable>, the more + frequently values close to the middle of the interval are drawn, and the + less frequently values close to the <replaceable>min</replaceable> and + <replaceable>max</replaceable> bounds. About 67% of values are drawn from the + middle <literal>1.0 / parameter</literal>, that is a relative + <literal>0.5 / parameter</literal> around the mean, and 95% in the middle + <literal>2.0 / parameter</literal>, that is a relative + <literal>1.0 / parameter</literal> around the mean; for instance, if + <replaceable>parameter</replaceable> is 4.0, 67% of values are drawn from the + middle quarter (1.0 / 4.0) of the interval (i.e., from + <literal>3.0 / 8.0</literal> to <literal>5.0 / 8.0</literal>) and 95% from + the middle half (<literal>2.0 / 4.0</literal>) of the interval (second and third + quartiles). The minimum allowed <replaceable>parameter</replaceable> + value is 2.0. + </para> + </listitem> + <listitem> + <para> + <literal>random_zipfian</literal> generates a bounded Zipfian + distribution. + <replaceable>parameter</replaceable> defines how skewed the distribution + is. The larger the <replaceable>parameter</replaceable>, 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 <replaceable>k</replaceable> + versus drawing <replaceable>k+1</replaceable> is + <literal>((<replaceable>k</replaceable>+1)/<replaceable>k</replaceable>)**<replaceable>parameter</replaceable></literal>. + For example, <literal>random_zipfian(1, ..., 2.5)</literal> produces + the value <literal>1</literal> about <literal>(2/1)**2.5 = + 5.66</literal> times more frequently than <literal>2</literal>, which + itself is produced <literal>(3/2)**2.5 = 2.76</literal> times more + frequently than <literal>3</literal>, and so on. + </para> + <para> + <application>pgbench</application>'s implementation is based on + "Non-Uniform Random Variate Generation", Luc Devroye, p. 550-551, + Springer 1986. Due to limitations of that algorithm, + the <replaceable>parameter</replaceable> value is restricted to + the range [1.001, 1000]. + </para> + </listitem> + </itemizedlist> + + <note> + <para> + 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. + </para> + <para> + To avoid this, you may wish to use the <function>permute</function> + function, or some other additional step with similar effect, to shuffle + the selected rows and remove such correlations. + </para> + </note> + + <para> + Hash functions <literal>hash</literal>, <literal>hash_murmur2</literal> and + <literal>hash_fnv1a</literal> accept an input value and an optional seed parameter. + In case the seed isn't provided the value of <literal>:default_seed</literal> + is used, which is initialized randomly unless set by the command-line + <literal>-D</literal> option. + </para> + + <para> + <literal>permute</literal> accepts an input value, a size, and an optional + seed parameter. It generates a pseudorandom permutation of integers in + the range <literal>[0, size)</literal>, and returns the index of the input + value in the permuted values. The permutation chosen is parameterized by + the seed, which defaults to <literal>:default_seed</literal>, if not + specified. Unlike the hash functions, <literal>permute</literal> 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. <function>permute</function> can be + used to scatter the distribution of non-uniform random functions such as + <literal>random_zipfian</literal> or <literal>random_exponential</literal> + so that values drawn more often are not trivially correlated. For + instance, the following <application>pgbench</application> script + simulates a possible real world workload typical for social media and + blogging platforms where a few accounts generate excessive load: + +<programlisting> +\set size 1000000 +\set r random_zipfian(1, :size, 1.07) +\set k 1 + permute(:r, :size) +</programlisting> + + 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: + +<programlisting> +\set k1 1 + permute(:r, :size, :default_seed + 123) +\set k2 1 + permute(:r, :size, :default_seed + 321) +</programlisting> + + A similar behavior can also be approximated with <function>hash</function>: + +<programlisting> +\set size 1000000 +\set r random_zipfian(1, 100 * :size, 1.07) +\set k 1 + abs(hash(:r)) % :size +</programlisting> + + However, since <function>hash</function> generates collisions, some values + will not be reachable and others will be more frequent than expected from + the original distribution. + </para> + + <para> + As an example, the full definition of the built-in TPC-B-like + transaction is: + +<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; +</programlisting> + + 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.) + </para> + + </refsect2> + + <refsect2> + <title>Per-Transaction Logging</title> + + <para> + With the <option>-l</option> option (but without + the <option>--aggregate-interval</option> option), + <application>pgbench</application> writes information about each transaction + to a log file. The log file will be named + <filename><replaceable>prefix</replaceable>.<replaceable>nnn</replaceable></filename>, + where <replaceable>prefix</replaceable> defaults to <literal>pgbench_log</literal>, and + <replaceable>nnn</replaceable> is the PID of the + <application>pgbench</application> process. + The prefix can be changed by using the <option>--log-prefix</option> option. + If the <option>-j</option> 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 + <filename><replaceable>prefix</replaceable>.<replaceable>nnn</replaceable>.<replaceable>mmm</replaceable></filename>, + where <replaceable>mmm</replaceable> is a sequential number for each worker starting + with 1. + </para> + + <para> + Each line in a log file describes one transaction. + It contains the following space-separated fields: + + <variablelist> + <varlistentry> + <term><replaceable>client_id</replaceable></term> + <listitem> + <para> + identifies the client session that ran the transaction + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>transaction_no</replaceable></term> + <listitem> + <para> + counts how many transactions have been run by that session + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>time</replaceable></term> + <listitem> + <para> + transaction's elapsed time, in microseconds + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>script_no</replaceable></term> + <listitem> + <para> + identifies the script file that was used for the transaction + (useful when multiple scripts are specified + with <option>-f</option> or <option>-b</option>) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>time_epoch</replaceable></term> + <listitem> + <para> + transaction's completion time, as a Unix-epoch time stamp + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>time_us</replaceable></term> + <listitem> + <para> + fractional-second part of transaction's completion time, in + microseconds + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>schedule_lag</replaceable></term> + <listitem> + <para> + 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 <option>--rate</option> is specified) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>retries</replaceable></term> + <listitem> + <para> + count of retries after serialization or deadlock errors during the + transaction + (present only if <option>--max-tries</option> is not equal to one) + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + When both <option>--rate</option> and <option>--latency-limit</option> are used, + the <replaceable>time</replaceable> for a skipped transaction will be reported as + <literal>skipped</literal>. + If the transaction ends with a failure, its <replaceable>time</replaceable> + will be reported as <literal>failed</literal>. If you use the + <option>--failures-detailed</option> option, the + <replaceable>time</replaceable> of the failed transaction will be reported as + <literal>serialization</literal> or + <literal>deadlock</literal> depending on the type of failure (see + <xref linkend="failures-and-retries"/> for more information). + </para> + + <para> + Here is a snippet of a log file generated in a single-client run: +<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 +</screen> + + Another example with <literal>--rate=100</literal> + and <literal>--latency-limit=5</literal> (note the additional + <replaceable>schedule_lag</replaceable> column): +<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 +</screen> + 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. + </para> + + <para> + 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 + <replaceable>retries</replaceable> column): +<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 +</screen> + </para> + + <para> + If the <option>--failures-detailed</option> option is used, the type of + failure is reported in the <replaceable>time</replaceable> like this: +<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 +</screen> + </para> + + <para> + When running a long test on hardware that can handle a lot of transactions, + the log files can become very large. The <option>--sampling-rate</option> option + can be used to log only a random sample of transactions. + </para> + </refsect2> + + <refsect2> + <title>Aggregated Logging</title> + + <para> + With the <option>--aggregate-interval</option> option, a different + format is used for the log files. Each log line describes one + aggregation interval. It contains the following space-separated + fields: + + <variablelist> + <varlistentry> + <term><replaceable>interval_start</replaceable></term> + <listitem> + <para> + start time of the interval, as a Unix-epoch time stamp + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>num_transactions</replaceable></term> + <listitem> + <para> + number of transactions within the interval + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>sum_latency</replaceable></term> + <listitem> + <para> + sum of transaction latencies + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>sum_latency_2</replaceable></term> + <listitem> + <para> + sum of squares of transaction latencies + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>min_latency</replaceable></term> + <listitem> + <para> + minimum transaction latency + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>max_latency</replaceable></term> + <listitem> + <para> + maximum transaction latency + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>sum_lag</replaceable></term> + <listitem> + <para> + sum of transaction start delays + (zero unless <option>--rate</option> is specified) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>sum_lag_2</replaceable></term> + <listitem> + <para> + sum of squares of transaction start delays + (zero unless <option>--rate</option> is specified) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>min_lag</replaceable></term> + <listitem> + <para> + minimum transaction start delay + (zero unless <option>--rate</option> is specified) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>max_lag</replaceable></term> + <listitem> + <para> + maximum transaction start delay + (zero unless <option>--rate</option> is specified) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>skipped</replaceable></term> + <listitem> + <para> + number of transactions skipped because they would have started too late + (zero unless <option>--rate</option> + and <option>--latency-limit</option> are specified) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>retried</replaceable></term> + <listitem> + <para> + number of retried transactions + (zero unless <option>--max-tries</option> is not equal to one) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>retries</replaceable></term> + <listitem> + <para> + number of retries after serialization or deadlock errors + (zero unless <option>--max-tries</option> is not equal to one) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>serialization_failures</replaceable></term> + <listitem> + <para> + number of transactions that got a serialization error and were not + retried afterwards + (zero unless <option>--failures-detailed</option> is specified) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable>deadlock_failures</replaceable></term> + <listitem> + <para> + number of transactions that got a deadlock error and were not + retried afterwards + (zero unless <option>--failures-detailed</option> is specified) + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + Here is some example output generated with these options: +<screen> +<userinput>pgbench --aggregate-interval=10 --time=20 --client=10 --log --rate=1000 --latency-limit=10 --failures-detailed --max-tries=10 test</userinput> + +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 +</screen> + </para> + + <para> + 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. + </para> + + </refsect2> + + <refsect2> + <title>Per-Statement Report</title> + + <para> + With the <option>-r</option> option, <application>pgbench</application> + collects the following statistics for each statement: + <itemizedlist> + <listitem> + <para> + <literal>latency</literal> — elapsed transaction time for each + statement. <application>pgbench</application> reports an average value + of all successful runs of the statement. + </para> + </listitem> + <listitem> + <para> + The number of failures in this statement. See + <xref linkend="failures-and-retries"/> for more information. + </para> + </listitem> + <listitem> + <para> + The number of retries after a serialization or a deadlock error in this + statement. See <xref linkend="failures-and-retries"/> for more information. + </para> + </listitem> + </itemizedlist> + </para> + + <para> + The report displays retry statistics only if the <option>--max-tries</option> + option is not equal to 1. + </para> + + <para> + All values are computed for each statement executed by every client and are + reported after the benchmark has finished. + </para> + + <para> + For the default script, the output will look similar to this: +<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; +</screen> + + Another example of output for the default script using serializable default + transaction isolation level (<command>PGOPTIONS='-c + default_transaction_isolation=serializable' pgbench ...</command>): +<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; +</screen></para> + + <para> + If multiple script files are specified, all statistics are reported + separately for each script file. + </para> + + <para> + 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. + </para> + </refsect2> + + <refsect2 id="failures-and-retries" xreflabel="Failures and Serialization/Deadlock Retries"> + <title>Failures and Serialization/Deadlock Retries</title> + + <para> + When executing <application>pgbench</application>, there are three main types + of errors: + <itemizedlist> + <listitem> + <para> + Errors of the main program. They are the most serious and always result + in an immediate exit from <application>pgbench</application> with the + corresponding error message. They include: + <itemizedlist> + <listitem> + <para> + errors at the beginning of <application>pgbench</application> + (e.g. an invalid option value); + </para> + </listitem> + <listitem> + <para> + errors in the initialization mode (e.g. the query to create + tables for built-in scripts fails); + </para> + </listitem> + <listitem> + <para> + errors before starting threads (e.g. could not connect to the + database server, syntax error in the meta command, thread + creation failure); + </para> + </listitem> + <listitem> + <para> + internal <application>pgbench</application> errors (which are + supposed to never occur...). + </para> + </listitem> + </itemizedlist></para> + </listitem> + <listitem> + <para> + 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. + </para> + </listitem> + <listitem> + <para> + Direct client errors. They lead to immediate exit from + <application>pgbench</application> with the corresponding error message + only in the case of an internal <application>pgbench</application> + 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 + <application>pgbench</application> errors. + </para> + </listitem> + </itemizedlist> + </para> + + <para> + 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 + <xref linkend="transactions-and-scripts"/> 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 <option>--max-tries</option> option) / the maximum + time of retries (specified by the <option>--latency-limit</option> option) / the end + of benchmark (specified by the <option>--time</option> option). If + the last trial run fails, this transaction will be reported as failed but + the client is not aborted and continues to work. + </para> + + <note> + <para> + Without specifying the <option>--max-tries</option> 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 (<literal>--max-tries=0</literal>) + and the <option>--latency-limit</option> option to limit only the maximum time + of tries. You can also use the <option>--time</option> option to limit the + benchmark duration under an unlimited number of tries. + </para> + <para> + Be careful when repeating scripts that contain multiple transactions: the + script is always retried completely, so successful transactions can be + performed several times. + </para> + <para> + 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 <command>\setshell</command> command. + </para> + </note> + + <para> + 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. + </para> + + <para> + The main report contains the number of failed transactions. If the + <option>--max-tries</option> 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 <option>--max-tries</option> option is not equal to 1. + </para> + + <para> + 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 + <option>--failures-detailed</option> 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 <option>--verbose-errors</option> + option. + </para> + </refsect2> + + <refsect2> + <title>Good Practices</title> + + <para> + It is very easy to use <application>pgbench</application> to produce completely + meaningless numbers. Here are some guidelines to help you get useful + results. + </para> + + <para> + In the first place, <emphasis>never</emphasis> believe any test that runs + for only a few seconds. Use the <option>-t</option> or <option>-T</option> 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. + </para> + + <para> + For the default TPC-B-like test scenario, the initialization scale factor + (<option>-s</option>) should be at least as large as the largest number of + clients you intend to test (<option>-c</option>); else you'll mostly be + measuring update contention. There are only <option>-s</option> rows in + the <structname>pgbench_branches</structname> table, and every transaction wants to + update one of them, so <option>-c</option> values in excess of <option>-s</option> + will undoubtedly result in lots of transactions blocked waiting for + other transactions. + </para> + + <para> + 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. + </para> + + <para> + A limitation of <application>pgbench</application> is that it can itself become + the bottleneck when trying to test a large number of client sessions. + This can be alleviated by running <application>pgbench</application> on a different + machine from the database server, although low network latency will be + essential. It might even be useful to run several <application>pgbench</application> + instances concurrently, on several client machines, against the same + database server. + </para> + </refsect2> + <refsect2> + <title>Security</title> + + <para> + If untrusted users have access to a database that has not adopted a + <link linkend="ddl-schemas-patterns">secure schema usage pattern</link>, + do not run <application>pgbench</application> in that + database. <application>pgbench</application> uses unqualified names and + does not manipulate the search path. + </para> + </refsect2> + </refsect1> +</refentry> |