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><H1
><A
NAME="PGBENCH"
></A
><SPAN
CLASS="APPLICATION"
>pgbench</SPAN
></H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN170509"
></A
><H2
>Name</H2
>pgbench -- run a benchmark test on <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
></DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN170513"
></A
><H2
>Synopsis</H2
><P
><TT
CLASS="COMMAND"
>pgbench</TT
> <TT
CLASS="OPTION"
>-i</TT
> [<TT
CLASS="REPLACEABLE"
><I
>option</I
></TT
>...] [<TT
CLASS="REPLACEABLE"
><I
>dbname</I
></TT
>]</P
><P
><TT
CLASS="COMMAND"
>pgbench</TT
> [<TT
CLASS="REPLACEABLE"
><I
>option</I
></TT
>...] [<TT
CLASS="REPLACEABLE"
><I
>dbname</I
></TT
>]</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN170528"
></A
><H2
>Description</H2
><P
> <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> is a simple program for running benchmark
tests on <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>. It runs the same sequence of SQL
commands over and over, possibly in multiple concurrent database sessions,
and then calculates the average transaction rate (transactions per second).
By default, <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> tests a scenario that is
loosely based on TPC-B, involving five <TT
CLASS="COMMAND"
>SELECT</TT
>,
<TT
CLASS="COMMAND"
>UPDATE</TT
>, and <TT
CLASS="COMMAND"
>INSERT</TT
> commands per transaction.
However, it is easy to test other cases by writing your own transaction
script files.
</P
><P
> Typical output from pgbench looks like:
</P><PRE
CLASS="SCREEN"
>transaction type: TPC-B (sort of)
scaling factor: 10
query mode: simple
number of clients: 10
number of threads: 1
number of transactions per client: 1000
number of transactions actually processed: 10000/10000
tps = 85.184871 (including connections establishing)
tps = 85.296346 (excluding connections establishing)</PRE
><P>
The first six lines report some of the most important parameter
settings. The next 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. (In <TT
CLASS="OPTION"
>-T</TT
> mode, only the actual
number of transactions is printed.)
The last two lines report the number of transactions per second,
figured with and without counting the time to start database sessions.
</P
><P
> The default TPC-B-like transaction test requires specific tables to be
set up beforehand. <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> should be invoked with
the <TT
CLASS="OPTION"
>-i</TT
> (initialize) option to create and populate these
tables. (When you are testing a custom script, you don't need this
step, but will instead need to do whatever setup your test needs.)
Initialization looks like:
</P><PRE
CLASS="PROGRAMLISTING"
>pgbench -i [<SPAN
CLASS="OPTIONAL"
> <TT
CLASS="REPLACEABLE"
><I
>other-options</I
></TT
> </SPAN
>] <TT
CLASS="REPLACEABLE"
><I
>dbname</I
></TT
></PRE
><P>
where <TT
CLASS="REPLACEABLE"
><I
>dbname</I
></TT
> is the name of the already-created
database to test in. (You may also need <TT
CLASS="OPTION"
>-h</TT
>,
<TT
CLASS="OPTION"
>-p</TT
>, and/or <TT
CLASS="OPTION"
>-U</TT
> options to specify how to
connect to the database server.)
</P
><DIV
CLASS="CAUTION"
><P
></P
><TABLE
CLASS="CAUTION"
BORDER="1"
WIDTH="100%"
><TR
><TD
ALIGN="CENTER"
><B
>Caution</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
><P
> <TT
CLASS="LITERAL"
>pgbench -i</TT
> creates four tables <TT
CLASS="STRUCTNAME"
>pgbench_accounts</TT
>,
<TT
CLASS="STRUCTNAME"
>pgbench_branches</TT
>, <TT
CLASS="STRUCTNAME"
>pgbench_history</TT
>, and
<TT
CLASS="STRUCTNAME"
>pgbench_tellers</TT
>,
destroying any existing tables of these names.
Be very careful to use another database if you have tables having these
names!
</P
></TD
></TR
></TABLE
></DIV
><P
> At the default <SPAN
CLASS="QUOTE"
>"scale factor"</SPAN
> of 1, the tables initially
contain this many rows:
</P><PRE
CLASS="SCREEN"
>table # of rows
---------------------------------
pgbench_branches 1
pgbench_tellers 10
pgbench_accounts 100000
pgbench_history 0</PRE
><P>
You can (and, for most purposes, probably should) increase the number
of rows by using the <TT
CLASS="OPTION"
>-s</TT
> (scale factor) option. The
<TT
CLASS="OPTION"
>-F</TT
> (fillfactor) option might also be used at this point.
</P
><P
> Once you have done the necessary setup, you can run your benchmark
with a command that doesn't include <TT
CLASS="OPTION"
>-i</TT
>, that is
</P><PRE
CLASS="PROGRAMLISTING"
>pgbench [<SPAN
CLASS="OPTIONAL"
> <TT
CLASS="REPLACEABLE"
><I
>options</I
></TT
> </SPAN
>] <TT
CLASS="REPLACEABLE"
><I
>dbname</I
></TT
></PRE
><P>
In nearly all cases, you'll need some options to make a useful test.
The most important options are <TT
CLASS="OPTION"
>-c</TT
> (number of clients),
<TT
CLASS="OPTION"
>-t</TT
> (number of transactions), <TT
CLASS="OPTION"
>-T</TT
> (time limit),
and <TT
CLASS="OPTION"
>-f</TT
> (specify a custom script file).
See below for a full list.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN170573"
></A
><H2
>Options</H2
><P
> The following is divided into three subsections: Different options are used
during database initialization and while running benchmarks, some options
are useful in both cases.
</P
><DIV
CLASS="REFSECT2"
><A
NAME="PGBENCH-INIT-OPTIONS"
></A
><H3
>Initialization Options</H3
><P
> <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> accepts the following command-line
initialization arguments:
<P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="OPTION"
>-i</TT
><BR><TT
CLASS="OPTION"
>--initialize</TT
></DT
><DD
><P
> Required to invoke initialization mode.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-F</TT
> <TT
CLASS="REPLACEABLE"
><I
>fillfactor</I
></TT
><BR><TT
CLASS="OPTION"
>--fillfactor=</TT
><TT
CLASS="REPLACEABLE"
><I
>fillfactor</I
></TT
></DT
><DD
><P
> Create the <TT
CLASS="STRUCTNAME"
>pgbench_accounts</TT
>,
<TT
CLASS="STRUCTNAME"
>pgbench_tellers</TT
> and
<TT
CLASS="STRUCTNAME"
>pgbench_branches</TT
> tables with the given fillfactor.
Default is 100.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-n</TT
><BR><TT
CLASS="OPTION"
>--no-vacuum</TT
></DT
><DD
><P
> Perform no vacuuming after initialization.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-q</TT
><BR><TT
CLASS="OPTION"
>--quiet</TT
></DT
><DD
><P
> Switch logging to quiet mode, producing only one progress message per 5
seconds. The default logging prints one message each 100000 rows, which
often outputs many lines per second (especially on good hardware).
</P
></DD
><DT
><TT
CLASS="OPTION"
>-s</TT
> <TT
CLASS="REPLACEABLE"
><I
>scale_factor</I
></TT
><BR><TT
CLASS="OPTION"
>--scale=</TT
><TT
CLASS="REPLACEABLE"
><I
>scale_factor</I
></TT
></DT
><DD
><P
> Multiply the number of rows generated by the scale factor.
For example, <TT
CLASS="LITERAL"
>-s 100</TT
> will create 10,000,000 rows
in the <TT
CLASS="STRUCTNAME"
>pgbench_accounts</TT
> table. Default is 1.
When the scale is 20,000 or larger, the columns used to
hold account identifiers (<TT
CLASS="STRUCTFIELD"
>aid</TT
> columns)
will switch to using larger integers (<TT
CLASS="TYPE"
>bigint</TT
>),
in order to be big enough to hold the range of account
identifiers.
</P
></DD
><DT
><TT
CLASS="OPTION"
>--foreign-keys</TT
></DT
><DD
><P
> Create foreign key constraints between the standard tables.
</P
></DD
><DT
><TT
CLASS="OPTION"
>--index-tablespace=<TT
CLASS="REPLACEABLE"
><I
>index_tablespace</I
></TT
></TT
></DT
><DD
><P
> Create indexes in the specified tablespace, rather than the default
tablespace.
</P
></DD
><DT
><TT
CLASS="OPTION"
>--tablespace=<TT
CLASS="REPLACEABLE"
><I
>tablespace</I
></TT
></TT
></DT
><DD
><P
> Create tables in the specified tablespace, rather than the default
tablespace.
</P
></DD
><DT
><TT
CLASS="OPTION"
>--unlogged-tables</TT
></DT
><DD
><P
> Create all tables as unlogged tables, rather than permanent tables.
</P
></DD
></DL
></DIV
><P>
</P
></DIV
><DIV
CLASS="REFSECT2"
><A
NAME="PGBENCH-RUN-OPTIONS"
></A
><H3
>Benchmarking Options</H3
><P
> <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> accepts the following command-line
benchmarking arguments:
<P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="OPTION"
>-c</TT
> <TT
CLASS="REPLACEABLE"
><I
>clients</I
></TT
><BR><TT
CLASS="OPTION"
>--client=</TT
><TT
CLASS="REPLACEABLE"
><I
>clients</I
></TT
></DT
><DD
><P
> Number of clients simulated, that is, number of concurrent database
sessions. Default is 1.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-C</TT
><BR><TT
CLASS="OPTION"
>--connect</TT
></DT
><DD
><P
> Establish a new connection for each transaction, rather than
doing it just once per client session.
This is useful to measure the connection overhead.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-d</TT
><BR><TT
CLASS="OPTION"
>--debug</TT
></DT
><DD
><P
> Print debugging output.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-D</TT
> <TT
CLASS="REPLACEABLE"
><I
>varname</I
></TT
><TT
CLASS="LITERAL"
>=</TT
><TT
CLASS="REPLACEABLE"
><I
>value</I
></TT
><BR><TT
CLASS="OPTION"
>--define=</TT
><TT
CLASS="REPLACEABLE"
><I
>varname</I
></TT
><TT
CLASS="LITERAL"
>=</TT
><TT
CLASS="REPLACEABLE"
><I
>value</I
></TT
></DT
><DD
><P
> Define a variable for use by a custom script (see below).
Multiple <TT
CLASS="OPTION"
>-D</TT
> options are allowed.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-f</TT
> <TT
CLASS="REPLACEABLE"
><I
>filename</I
></TT
><BR><TT
CLASS="OPTION"
>--file=</TT
><TT
CLASS="REPLACEABLE"
><I
>filename</I
></TT
></DT
><DD
><P
> Read transaction script from <TT
CLASS="REPLACEABLE"
><I
>filename</I
></TT
>.
See below for details.
<TT
CLASS="OPTION"
>-N</TT
>, <TT
CLASS="OPTION"
>-S</TT
>, and <TT
CLASS="OPTION"
>-f</TT
>
are mutually exclusive.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-j</TT
> <TT
CLASS="REPLACEABLE"
><I
>threads</I
></TT
><BR><TT
CLASS="OPTION"
>--jobs=</TT
><TT
CLASS="REPLACEABLE"
><I
>threads</I
></TT
></DT
><DD
><P
> Number of worker threads within <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
>.
Using more than one thread can be helpful on multi-CPU machines.
The number of clients must be a multiple of the number of threads,
since each thread is given the same number of client sessions to manage.
Default is 1.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-l</TT
><BR><TT
CLASS="OPTION"
>--log</TT
></DT
><DD
><P
> Write the time taken by each transaction to a log file.
See below for details.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-M</TT
> <TT
CLASS="REPLACEABLE"
><I
>querymode</I
></TT
><BR><TT
CLASS="OPTION"
>--protocol=</TT
><TT
CLASS="REPLACEABLE"
><I
>querymode</I
></TT
></DT
><DD
><P
> Protocol to use for submitting queries to the server:
<P
></P
></P><UL
><LI
><P
><TT
CLASS="LITERAL"
>simple</TT
>: use simple query protocol.</P
></LI
><LI
><P
><TT
CLASS="LITERAL"
>extended</TT
>: use extended query protocol.</P
></LI
><LI
><P
><TT
CLASS="LITERAL"
>prepared</TT
>: use extended query protocol with prepared statements.</P
></LI
></UL
><P>
The default is simple query protocol. (See <A
HREF="protocol.html"
>Chapter 49</A
>
for more information.)
</P
></DD
><DT
><TT
CLASS="OPTION"
>-n</TT
><BR><TT
CLASS="OPTION"
>--no-vacuum</TT
></DT
><DD
><P
> Perform no vacuuming before running the test.
This option is <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>necessary</I
></SPAN
>
if you are running a custom test scenario that does not include
the standard tables <TT
CLASS="STRUCTNAME"
>pgbench_accounts</TT
>,
<TT
CLASS="STRUCTNAME"
>pgbench_branches</TT
>, <TT
CLASS="STRUCTNAME"
>pgbench_history</TT
>, and
<TT
CLASS="STRUCTNAME"
>pgbench_tellers</TT
>.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-N</TT
><BR><TT
CLASS="OPTION"
>--skip-some-updates</TT
></DT
><DD
><P
> Do not update <TT
CLASS="STRUCTNAME"
>pgbench_tellers</TT
> and
<TT
CLASS="STRUCTNAME"
>pgbench_branches</TT
>.
This will avoid update contention on these tables, but
it makes the test case even less like TPC-B.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-P</TT
> <TT
CLASS="REPLACEABLE"
><I
>sec</I
></TT
><BR><TT
CLASS="OPTION"
>--progress=</TT
><TT
CLASS="REPLACEABLE"
><I
>sec</I
></TT
></DT
><DD
><P
> Show progress report every <TT
CLASS="LITERAL"
>sec</TT
> seconds. The report
includes the time since the beginning of the run, the tps since the
last report, and the transaction latency average and standard
deviation since the last report. Under throttling (<TT
CLASS="OPTION"
>-R</TT
>),
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.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-r</TT
><BR><TT
CLASS="OPTION"
>--report-latencies</TT
></DT
><DD
><P
> Report the average per-statement latency (execution time from the
perspective of the client) of each command after the benchmark
finishes. See below for details.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-R</TT
> <TT
CLASS="REPLACEABLE"
><I
>rate</I
></TT
><BR><TT
CLASS="OPTION"
>--rate=</TT
><TT
CLASS="REPLACEABLE"
><I
>rate</I
></TT
></DT
><DD
><P
> Execute transactions targeting the specified rate instead of running
as fast as possible (the default). The rate is given in transactions
per second. If the targeted rate is above the maximum possible rate,
the rate limit won't impact the results.
</P
><P
> The rate is targeted by starting transactions along a
Poisson-distributed schedule time line. The expected start time
schedule moves forward based on when the client first started, not
when the previous transaction ended. That approach means that when
transactions go past their original scheduled end time, it is
possible for later ones to catch up again.
</P
><P
> When throttling is active, the transaction latency reported at the
end of the run is calculated from the scheduled start times, so it
includes the time each transaction had to wait for the previous
transaction to finish. The wait time is called the schedule lag time,
and its average and maximum are also reported separately. The
transaction latency with respect to the actual transaction start time,
i.e. the time spent executing the transaction in the database, can be
computed by subtracting the schedule lag time from the reported
latency.
</P
><P
> A high schedule lag time is an indication that the system cannot
process transactions at the specified rate, with the chosen number of
clients and threads. When the average transaction execution time is
longer than the scheduled interval between each transaction, each
successive transaction will fall further behind, and the schedule lag
time will keep increasing the longer the test run is. When that
happens, you will have to reduce the specified transaction rate.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-s</TT
> <TT
CLASS="REPLACEABLE"
><I
>scale_factor</I
></TT
><BR><TT
CLASS="OPTION"
>--scale=</TT
><TT
CLASS="REPLACEABLE"
><I
>scale_factor</I
></TT
></DT
><DD
><P
> Report the specified scale factor in <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
>'s
output. With the built-in tests, this is not necessary; the
correct scale factor will be detected by counting the number of
rows in the <TT
CLASS="STRUCTNAME"
>pgbench_branches</TT
> table. However, when testing
custom benchmarks (<TT
CLASS="OPTION"
>-f</TT
> option), the scale factor
will be reported as 1 unless this option is used.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-S</TT
><BR><TT
CLASS="OPTION"
>--select-only</TT
></DT
><DD
><P
> Perform select-only transactions instead of TPC-B-like test.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-t</TT
> <TT
CLASS="REPLACEABLE"
><I
>transactions</I
></TT
><BR><TT
CLASS="OPTION"
>--transactions=</TT
><TT
CLASS="REPLACEABLE"
><I
>transactions</I
></TT
></DT
><DD
><P
> Number of transactions each client runs. Default is 10.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-T</TT
> <TT
CLASS="REPLACEABLE"
><I
>seconds</I
></TT
><BR><TT
CLASS="OPTION"
>--time=</TT
><TT
CLASS="REPLACEABLE"
><I
>seconds</I
></TT
></DT
><DD
><P
> Run the test for this many seconds, rather than a fixed number of
transactions per client. <TT
CLASS="OPTION"
>-t</TT
> and
<TT
CLASS="OPTION"
>-T</TT
> are mutually exclusive.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-v</TT
><BR><TT
CLASS="OPTION"
>--vacuum-all</TT
></DT
><DD
><P
> Vacuum all four standard tables before running the test.
With neither <TT
CLASS="OPTION"
>-n</TT
> nor <TT
CLASS="OPTION"
>-v</TT
>, pgbench will vacuum the
<TT
CLASS="STRUCTNAME"
>pgbench_tellers</TT
> and <TT
CLASS="STRUCTNAME"
>pgbench_branches</TT
>
tables, and will truncate <TT
CLASS="STRUCTNAME"
>pgbench_history</TT
>.
</P
></DD
><DT
><TT
CLASS="OPTION"
>--aggregate-interval=<TT
CLASS="REPLACEABLE"
><I
>seconds</I
></TT
></TT
></DT
><DD
><P
> Length of aggregation interval (in seconds). May be used only together
with <SPAN
CLASS="APPLICATION"
>-l</SPAN
> - with this option, the log contains
per-interval summary (number of transactions, min/max latency and two
additional fields useful for variance estimation).
</P
><P
> This option is not currently supported on Windows.
</P
></DD
><DT
><TT
CLASS="OPTION"
>--sampling-rate=<TT
CLASS="REPLACEABLE"
><I
>rate</I
></TT
></TT
></DT
><DD
><P
> Sampling rate, used when writing data into the log, to reduce the
amount of log generated. If this option is given, only the specified
fraction of transactions are logged. 1.0 means all transactions will
be logged, 0.05 means only 5% of the transactions will be logged.
</P
><P
> Remember to take the sampling rate into account when processing the
log file. For example, when computing tps values, you need to multiply
the numbers accordingly (e.g. with 0.01 sample rate, you'll only get
1/100 of the actual tps).
</P
></DD
></DL
></DIV
><P>
</P
></DIV
><DIV
CLASS="REFSECT2"
><A
NAME="PGBENCH-COMMON-OPTIONS"
></A
><H3
>Common Options</H3
><P
> <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> accepts the following command-line
common arguments:
<P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="OPTION"
>-h</TT
> <TT
CLASS="REPLACEABLE"
><I
>hostname</I
></TT
><BR><TT
CLASS="OPTION"
>--host=</TT
><TT
CLASS="REPLACEABLE"
><I
>hostname</I
></TT
></DT
><DD
><P
> The database server's host name
</P
></DD
><DT
><TT
CLASS="OPTION"
>-p</TT
> <TT
CLASS="REPLACEABLE"
><I
>port</I
></TT
><BR><TT
CLASS="OPTION"
>--port=</TT
><TT
CLASS="REPLACEABLE"
><I
>port</I
></TT
></DT
><DD
><P
> The database server's port number
</P
></DD
><DT
><TT
CLASS="OPTION"
>-U</TT
> <TT
CLASS="REPLACEABLE"
><I
>login</I
></TT
><BR><TT
CLASS="OPTION"
>--username=</TT
><TT
CLASS="REPLACEABLE"
><I
>login</I
></TT
></DT
><DD
><P
> The user name to connect as
</P
></DD
><DT
><TT
CLASS="OPTION"
>-V</TT
><BR><TT
CLASS="OPTION"
>--version</TT
></DT
><DD
><P
> Print the <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> version and exit.
</P
></DD
><DT
><TT
CLASS="OPTION"
>-?</TT
><BR><TT
CLASS="OPTION"
>--help</TT
></DT
><DD
><P
> Show help about <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> command line
arguments, and exit.
</P
></DD
></DL
></DIV
><P>
</P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN170906"
></A
><H2
>Notes</H2
><DIV
CLASS="REFSECT2"
><A
NAME="AEN170908"
></A
><H3
>What is the <SPAN
CLASS="QUOTE"
>"Transaction"</SPAN
> Actually Performed in pgbench?</H3
><P
> The default transaction script issues seven commands per transaction:
</P
><P
></P
><OL
TYPE="1"
><LI
><P
><TT
CLASS="LITERAL"
>BEGIN;</TT
></P
></LI
><LI
><P
><TT
CLASS="LITERAL"
>UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;</TT
></P
></LI
><LI
><P
><TT
CLASS="LITERAL"
>SELECT abalance FROM pgbench_accounts WHERE aid = :aid;</TT
></P
></LI
><LI
><P
><TT
CLASS="LITERAL"
>UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;</TT
></P
></LI
><LI
><P
><TT
CLASS="LITERAL"
>UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid;</TT
></P
></LI
><LI
><P
><TT
CLASS="LITERAL"
>INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta, CURRENT_TIMESTAMP);</TT
></P
></LI
><LI
><P
><TT
CLASS="LITERAL"
>END;</TT
></P
></LI
></OL
><P
> If you specify <TT
CLASS="OPTION"
>-N</TT
>, steps 4 and 5 aren't included in the
transaction. If you specify <TT
CLASS="OPTION"
>-S</TT
>, only the <TT
CLASS="COMMAND"
>SELECT</TT
> is
issued.
</P
></DIV
><DIV
CLASS="REFSECT2"
><A
NAME="AEN170938"
></A
><H3
>Custom Scripts</H3
><P
> <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> has support for running custom
benchmark scenarios by replacing the default transaction script
(described above) with a transaction script read from a file
(<TT
CLASS="OPTION"
>-f</TT
> option). In this case a <SPAN
CLASS="QUOTE"
>"transaction"</SPAN
>
counts as one execution of a script file. You can even specify
multiple scripts (multiple <TT
CLASS="OPTION"
>-f</TT
> options), in which
case a random one of the scripts is chosen each time a client session
starts a new transaction.
</P
><P
> The format of a script file is one SQL command per line; multiline
SQL commands are not supported. Empty lines and lines beginning with
<TT
CLASS="LITERAL"
>--</TT
> are ignored. Script file lines can also be
<SPAN
CLASS="QUOTE"
>"meta commands"</SPAN
>, which are interpreted by <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
>
itself, as described below.
</P
><P
> There is a simple variable-substitution facility for script files.
Variables can be set by the command-line <TT
CLASS="OPTION"
>-D</TT
> option,
explained above, or by the meta commands explained below.
In addition to any variables preset by <TT
CLASS="OPTION"
>-D</TT
> command-line options,
there are a few variables that are preset automatically, listed in
<A
HREF="pgbench.html#PGBENCH-AUTOMATIC-VARIABLES"
>Table G-1</A
>. A value specified for these
variables using <TT
CLASS="OPTION"
>-D</TT
> takes precedence over the automatic presets.
Once set, a variable's
value can be inserted into a SQL command by writing
<TT
CLASS="LITERAL"
>:</TT
><TT
CLASS="REPLACEABLE"
><I
>variablename</I
></TT
>. When running more than
one client session, each session has its own set of variables.
</P
><DIV
CLASS="TABLE"
><A
NAME="PGBENCH-AUTOMATIC-VARIABLES"
></A
><P
><B
>Table G-1. Automatic variables</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><THEAD
><TR
><TH
>Variable</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
> <TT
CLASS="LITERAL"
>scale</TT
> </TD
><TD
>current scale factor</TD
></TR
><TR
><TD
> <TT
CLASS="LITERAL"
>client_id</TT
> </TD
><TD
>unique number identifying the client session (starts from zero)</TD
></TR
></TBODY
></TABLE
></DIV
><P
> Script file meta commands begin with a backslash (<TT
CLASS="LITERAL"
>\</TT
>).
Arguments to a meta command are separated by white space.
These meta commands are supported:
</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>\set <TT
CLASS="REPLACEABLE"
><I
>varname</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>operand1</I
></TT
> [ <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>operand2</I
></TT
> ]</TT
></DT
><DD
><P
> Sets variable <TT
CLASS="REPLACEABLE"
><I
>varname</I
></TT
> to a calculated integer value.
Each <TT
CLASS="REPLACEABLE"
><I
>operand</I
></TT
> is either an integer constant or a
<TT
CLASS="LITERAL"
>:</TT
><TT
CLASS="REPLACEABLE"
><I
>variablename</I
></TT
> reference to a variable
having an integer value. The <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
> can be
<TT
CLASS="LITERAL"
>+</TT
>, <TT
CLASS="LITERAL"
>-</TT
>, <TT
CLASS="LITERAL"
>*</TT
>, or <TT
CLASS="LITERAL"
>/</TT
>.
</P
><P
> Example:
</P><PRE
CLASS="PROGRAMLISTING"
>\set ntellers 10 * :scale</PRE
><P></P
></DD
><DT
><TT
CLASS="LITERAL"
>\setrandom <TT
CLASS="REPLACEABLE"
><I
>varname</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>min</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>max</I
></TT
></TT
></DT
><DD
><P
> Sets variable <TT
CLASS="REPLACEABLE"
><I
>varname</I
></TT
> to a random integer value
between the limits <TT
CLASS="REPLACEABLE"
><I
>min</I
></TT
> and <TT
CLASS="REPLACEABLE"
><I
>max</I
></TT
> inclusive.
Each limit can be either an integer constant or a
<TT
CLASS="LITERAL"
>:</TT
><TT
CLASS="REPLACEABLE"
><I
>variablename</I
></TT
> reference to a variable
having an integer value.
</P
><P
> Example:
</P><PRE
CLASS="PROGRAMLISTING"
>\setrandom aid 1 :naccounts</PRE
><P></P
></DD
><DT
><TT
CLASS="LITERAL"
>\sleep <TT
CLASS="REPLACEABLE"
><I
>number</I
></TT
> [ us | ms | s ]</TT
></DT
><DD
><P
> Causes script execution to sleep for the specified duration in
microseconds (<TT
CLASS="LITERAL"
>us</TT
>), milliseconds (<TT
CLASS="LITERAL"
>ms</TT
>) or seconds
(<TT
CLASS="LITERAL"
>s</TT
>). If the unit is omitted then seconds are the default.
<TT
CLASS="REPLACEABLE"
><I
>number</I
></TT
> can be either an integer constant or a
<TT
CLASS="LITERAL"
>:</TT
><TT
CLASS="REPLACEABLE"
><I
>variablename</I
></TT
> reference to a variable
having an integer value.
</P
><P
> Example:
</P><PRE
CLASS="PROGRAMLISTING"
>\sleep 10 ms</PRE
><P></P
></DD
><DT
><TT
CLASS="LITERAL"
>\setshell <TT
CLASS="REPLACEABLE"
><I
>varname</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>command</I
></TT
> [ <TT
CLASS="REPLACEABLE"
><I
>argument</I
></TT
> ... ]</TT
></DT
><DD
><P
> Sets variable <TT
CLASS="REPLACEABLE"
><I
>varname</I
></TT
> to the result of the shell command
<TT
CLASS="REPLACEABLE"
><I
>command</I
></TT
>. The command must return an integer value
through its standard output.
</P
><P
><TT
CLASS="REPLACEABLE"
><I
>argument</I
></TT
> can be either a text constant or a
<TT
CLASS="LITERAL"
>:</TT
><TT
CLASS="REPLACEABLE"
><I
>variablename</I
></TT
> reference to a variable of
any types. If you want to use <TT
CLASS="REPLACEABLE"
><I
>argument</I
></TT
> starting with
colons, you need to add an additional colon at the beginning of
<TT
CLASS="REPLACEABLE"
><I
>argument</I
></TT
>.
</P
><P
> Example:
</P><PRE
CLASS="PROGRAMLISTING"
>\setshell variable_to_be_assigned command literal_argument :variable ::literal_starting_with_colon</PRE
><P></P
></DD
><DT
><TT
CLASS="LITERAL"
>\shell <TT
CLASS="REPLACEABLE"
><I
>command</I
></TT
> [ <TT
CLASS="REPLACEABLE"
><I
>argument</I
></TT
> ... ]</TT
></DT
><DD
><P
> Same as <TT
CLASS="LITERAL"
>\setshell</TT
>, but the result is ignored.
</P
><P
> Example:
</P><PRE
CLASS="PROGRAMLISTING"
>\shell command literal_argument :variable ::literal_starting_with_colon</PRE
><P></P
></DD
></DL
></DIV
><P
> As an example, the full definition of the built-in TPC-B-like
transaction is:
</P><PRE
CLASS="PROGRAMLISTING"
>\set nbranches :scale
\set ntellers 10 * :scale
\set naccounts 100000 * :scale
\setrandom aid 1 :naccounts
\setrandom bid 1 :nbranches
\setrandom tid 1 :ntellers
\setrandom delta -5000 5000
BEGIN;
UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;
SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;
UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid;
INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta, CURRENT_TIMESTAMP);
END;</PRE
><P>
This script allows each iteration of the transaction to reference
different, randomly-chosen rows. (This example also shows why it's
important for each client session to have its own variables —
otherwise they'd not be independently touching different rows.)
</P
></DIV
><DIV
CLASS="REFSECT2"
><A
NAME="AEN171054"
></A
><H3
>Per-Transaction Logging</H3
><P
> With the <TT
CLASS="OPTION"
>-l</TT
> option but without the <TT
CLASS="OPTION"
>--aggregate-interval</TT
>,
<SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> writes the time taken by each transaction
to a log file. The log file will be named
<TT
CLASS="FILENAME"
>pgbench_log.<TT
CLASS="REPLACEABLE"
><I
>nnn</I
></TT
></TT
>, where
<TT
CLASS="REPLACEABLE"
><I
>nnn</I
></TT
> is the PID of the pgbench process.
If the <TT
CLASS="OPTION"
>-j</TT
> option is 2 or higher, creating 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
<TT
CLASS="FILENAME"
>pgbench_log.<TT
CLASS="REPLACEABLE"
><I
>nnn</I
></TT
>.<TT
CLASS="REPLACEABLE"
><I
>mmm</I
></TT
></TT
>,
where <TT
CLASS="REPLACEABLE"
><I
>mmm</I
></TT
> is a sequential number for each worker starting
with 1.
</P
><P
> The format of the log is:
</P><PRE
CLASS="SYNOPSIS"
><TT
CLASS="REPLACEABLE"
><I
>client_id</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>transaction_no</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>time</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>file_no</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>time_epoch</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>time_us</I
></TT
> [<TT
CLASS="REPLACEABLE"
><I
>schedule_lag</I
></TT
>]</PRE
><P>
where <TT
CLASS="REPLACEABLE"
><I
>time</I
></TT
> is the total elapsed transaction time in microseconds,
<TT
CLASS="REPLACEABLE"
><I
>file_no</I
></TT
> identifies which script file was used
(useful when multiple scripts were specified with <TT
CLASS="OPTION"
>-f</TT
>),
and <TT
CLASS="REPLACEABLE"
><I
>time_epoch</I
></TT
>/<TT
CLASS="REPLACEABLE"
><I
>time_us</I
></TT
> are a
UNIX epoch format timestamp and an offset
in microseconds (suitable for creating an ISO 8601
timestamp with fractional seconds) showing when
the transaction completed. The last field, <TT
CLASS="REPLACEABLE"
><I
>schedule_lag</I
></TT
>, is
the difference between the transaction's scheduled start time, and the
time it actually started, in microseconds. It is only present when the
<TT
CLASS="OPTION"
>--rate</TT
> option is used.
</P
><P
> Here are example outputs:
</P><PRE
CLASS="SCREEN"
> 0 199 2241 0 1175850568 995598
0 200 2465 0 1175850568 998079
0 201 2513 0 1175850569 608
0 202 2038 0 1175850569 2663</PRE
><P></P
><P
> When running a long test on hardware that can handle a lot of transactions,
the log files can become very large. The <TT
CLASS="OPTION"
>--sampling-rate</TT
> option
can be used to log only a random sample of transactions.
</P
></DIV
><DIV
CLASS="REFSECT2"
><A
NAME="AEN171088"
></A
><H3
>Aggregated Logging</H3
><P
> With the <TT
CLASS="OPTION"
>--aggregate-interval</TT
> option, the logs use a bit different format:
</P><PRE
CLASS="SYNOPSIS"
><TT
CLASS="REPLACEABLE"
><I
>interval_start</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>num_of_transactions</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>latency_sum</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>latency_2_sum</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>min_latency</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>max_latency</I
></TT
> [<TT
CLASS="REPLACEABLE"
><I
>lag_sum</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>lag_2_sum</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>min_lag</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>max_lag</I
></TT
>]</PRE
><P>
where <TT
CLASS="REPLACEABLE"
><I
>interval_start</I
></TT
> is the start of the interval (UNIX epoch
format timestamp), <TT
CLASS="REPLACEABLE"
><I
>num_of_transactions</I
></TT
> is the number of transactions
within the interval, <TT
CLASS="REPLACEABLE"
><I
>latency_sum</I
></TT
> is a sum of latencies
(so you can compute average latency easily). The following two fields are useful
for variance estimation - <TT
CLASS="REPLACEABLE"
><I
>latency_sum</I
></TT
> is a sum of latencies and
<TT
CLASS="REPLACEABLE"
><I
>latency_2_sum</I
></TT
> is a sum of 2nd powers of latencies. The next two
fields are <TT
CLASS="REPLACEABLE"
><I
>min_latency</I
></TT
> - a minimum latency within the interval, and
<TT
CLASS="REPLACEABLE"
><I
>max_latency</I
></TT
> - maximum latency within the interval. A transaction is
counted into the interval when it was committed. The last four fields,
<TT
CLASS="REPLACEABLE"
><I
>lag_sum</I
></TT
>, <TT
CLASS="REPLACEABLE"
><I
>lag_2_sum</I
></TT
>, <TT
CLASS="REPLACEABLE"
><I
>min_lag</I
></TT
>, and <TT
CLASS="REPLACEABLE"
><I
>max_lag</I
></TT
>, are only present if the --rate option is used.
They are calculated from the time each transaction had to wait for the
previous one to finish, i.e. the difference between each transaction's
scheduled start time and the time it actually started.
</P
><P
> Here is example output:
</P><PRE
CLASS="SCREEN"
>1345828501 5601 1542744 483552416 61 2573
1345828503 7884 1979812 565806736 60 1479
1345828505 7208 1979422 567277552 59 1391
1345828507 7685 1980268 569784714 60 1398
1345828509 7073 1979779 573489941 236 1411</PRE
><P></P
><P
> Notice that while the plain (unaggregated) log file contains a reference
to the custom script files, the aggregated log does not. Therefore if
you need per script data, you need to aggregate the data on your own.
</P
></DIV
><DIV
CLASS="REFSECT2"
><A
NAME="AEN171117"
></A
><H3
>Per-Statement Latencies</H3
><P
> With the <TT
CLASS="OPTION"
>-r</TT
> option, <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> collects
the elapsed transaction time of each statement executed by every
client. It then reports an average of those values, referred to
as the latency for each statement, after the benchmark has finished.
</P
><P
> For the default script, the output will look similar to this:
</P><PRE
CLASS="SCREEN"
>starting vacuum...end.
transaction type: TPC-B (sort of)
scaling factor: 1
query mode: simple
number of clients: 10
number of threads: 1
number of transactions per client: 1000
number of transactions actually processed: 10000/10000
tps = 618.764555 (including connections establishing)
tps = 622.977698 (excluding connections establishing)
statement latencies in milliseconds:
0.004386 \set nbranches 1 * :scale
0.001343 \set ntellers 10 * :scale
0.001212 \set naccounts 100000 * :scale
0.001310 \setrandom aid 1 :naccounts
0.001073 \setrandom bid 1 :nbranches
0.001005 \setrandom tid 1 :ntellers
0.001078 \setrandom delta -5000 5000
0.326152 BEGIN;
0.603376 UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;
0.454643 SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
5.528491 UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;
7.335435 UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid;
0.371851 INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta, CURRENT_TIMESTAMP);
1.212976 END;</PRE
><P>
</P
><P
> If multiple script files are specified, the averages are reported
separately for each script file.
</P
><P
> Note that collecting the additional timing information needed for
per-statement latency computation adds some overhead. This will slow
average execution speed and lower the computed TPS. The amount
of slowdown varies significantly depending on platform and hardware.
Comparing average TPS values with and without latency reporting enabled
is a good way to measure if the timing overhead is significant.
</P
></DIV
><DIV
CLASS="REFSECT2"
><A
NAME="AEN171126"
></A
><H3
>Good Practices</H3
><P
> It is very easy to use <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> to produce completely
meaningless numbers. Here are some guidelines to help you get useful
results.
</P
><P
> In the first place, <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>never</I
></SPAN
> believe any test that runs
for only a few seconds. Use the <TT
CLASS="OPTION"
>-t</TT
> or <TT
CLASS="OPTION"
>-T</TT
> option
to make the run last at least a few minutes, so as to average out noise.
In some cases you could need hours to get numbers that are reproducible.
It's a good idea to try the test run a few times, to find out if your
numbers are reproducible or not.
</P
><P
> For the default TPC-B-like test scenario, the initialization scale factor
(<TT
CLASS="OPTION"
>-s</TT
>) should be at least as large as the largest number of
clients you intend to test (<TT
CLASS="OPTION"
>-c</TT
>); else you'll mostly be
measuring update contention. There are only <TT
CLASS="OPTION"
>-s</TT
> rows in
the <TT
CLASS="STRUCTNAME"
>pgbench_branches</TT
> table, and every transaction wants to
update one of them, so <TT
CLASS="OPTION"
>-c</TT
> values in excess of <TT
CLASS="OPTION"
>-s</TT
>
will undoubtedly result in lots of transactions blocked waiting for
other transactions.
</P
><P
> The default test scenario is also quite sensitive to how long it's been
since the tables were initialized: accumulation of dead rows and dead space
in the tables changes the results. To understand the results you must keep
track of the total number of updates and when vacuuming happens. If
autovacuum is enabled it can result in unpredictable changes in measured
performance.
</P
><P
> A limitation of <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> is that it can itself become
the bottleneck when trying to test a large number of client sessions.
This can be alleviated by running <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
> on a different
machine from the database server, although low network latency will be
essential. It might even be useful to run several <SPAN
CLASS="APPLICATION"
>pgbench</SPAN
>
instances concurrently, on several client machines, against the same
database server.
</P
></DIV
></DIV
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