diff --git a/doc/src/sgml/pgbench.sgml b/doc/src/sgml/pgbench.sgml
index cb94e30c01..50c98b658f 100644
--- a/doc/src/sgml/pgbench.sgml
+++ b/doc/src/sgml/pgbench.sgml
@@ -1,640 +1,640 @@
-
-
-
- pgbench
-
-
- pgbench
-
-
-
- pgbench is a simple program for running benchmark
- tests on PostgreSQL. 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, pgbench tests a scenario that is
- loosely based on TPC-B, involving five SELECT,
- UPDATE, and INSERT commands per transaction.
- However, it is easy to test other cases by writing your own transaction
- script files.
-
-
-
- Typical output from pgbench looks like:
-
-
-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)
-
-
- 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. The last two lines report the TPS rate,
- figured with and without counting the time to start database sessions.
-
-
-
- Overview
-
-
- The default TPC-B-like transaction test requires specific tables to be
- set up beforehand. pgbench should be invoked with
- the -i (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:
-
-
-pgbench -i other-options dbname
-
-
- where dbname is the name of the already-created
- database to test in. (You may also need -h,
- -p, and/or -U options to specify how to
- connect to the database server.)
-
-
-
-
- pgbench -i creates four tables pgbench_accounts,
- pgbench_branches, pgbench_history, and
- pgbench_tellers,
- destroying any existing tables of these names.
- Be very careful to use another database if you have tables having these
- names!
-
-
-
-
- At the default scale factor of 1, the tables initially
- contain this many rows:
-
-
-table # of rows
----------------------------------
-pgbench_branches 1
-pgbench_tellers 10
-pgbench_accounts 100000
-pgbench_history 0
-
-
- You can (and, for most purposes, probably should) increase the number
- of rows by using the -s (scale factor) option. The
- -F (fillfactor) option might also be used at this point.
-
-
-
- Once you have done the necessary setup, you can run your benchmark
- with a command that doesn't include -i, that is
-
-
-pgbench options dbname
-
-
- In nearly all cases, you'll need some options to make a useful test.
- The most important options are -c (number of clients),
- -t (number of transactions), -T (time limit),
- and -f (specify a custom script file).
- See below for a full list.
-
-
-
- shows options that are used
- during database initialization, while
- shows options that are used
- while running benchmarks, and
- shows options that are useful
- in both cases.
-
-
-
- <application>pgbench</application> initialization options
-
-
-
- Option
- Description
-
-
-
-
-
- -i
-
- Required to invoke initialization mode.
-
-
-
- -s scale_factor
-
- Multiply the number of rows generated by the scale factor.
- For example, -s 100 will create 10,000,000 rows
- in the pgbench_accounts table. Default is 1.
-
-
-
- -F fillfactor
-
- Create the pgbench_accounts,
- pgbench_tellers and
- pgbench_branches tables with the given fillfactor.
- Default is 100.
-
-
-
-
-
-
-
- <application>pgbench</application> benchmarking options
-
-
-
- Option
- Description
-
-
-
-
-
- -c clients
-
- Number of clients simulated, that is, number of concurrent database
- sessions. Default is 1.
-
-
-
- -j threads
-
- Number of worker threads within pgbench.
- 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.
-
-
-
- -t transactions
-
- Number of transactions each client runs. Default is 10.
-
-
-
- -T seconds
-
- Run the test for this many seconds, rather than a fixed number of
- transactions per client. -t and
- -T are mutually exclusive.
-
-
-
- -M querymode
-
- Protocol to use for submitting queries to the server:
-
-
- simple: use simple query protocol.
-
-
- extended: use extended query protocol.
-
-
- prepared: use extended query protocol with prepared statements.
-
-
- The default is simple query protocol. (See
- for more information.)
-
-
-
- -N
-
- Do not update pgbench_tellers and
- pgbench_branches.
- This will avoid update contention on these tables, but
- it makes the test case even less like TPC-B.
-
-
-
- -S
-
- Perform select-only transactions instead of TPC-B-like test.
-
-
-
- -f filename
-
- Read transaction script from filename.
- See below for details.
- -N, -S, and -f
- are mutually exclusive.
-
-
-
- -n
-
- Perform no vacuuming before running the test.
- This option is necessary
- if you are running a custom test scenario that does not include
- the standard tables pgbench_accounts,
- pgbench_branches, pgbench_history, and
- pgbench_tellers.
-
-
-
- -v
-
- Vacuum all four standard tables before running the test.
- With neither -n nor -v, pgbench will vacuum the
- pgbench_tellers and pgbench_branches
- tables, and will truncate pgbench_history.
-
-
-
- -D varname=value
-
- Define a variable for use by a custom script (see below).
- Multiple -D options are allowed.
-
-
-
- -C
-
- Establish a new connection for each transaction, rather than
- doing it just once per client session.
- This is useful to measure the connection overhead.
-
-
-
- -l
-
- Write the time taken by each transaction to a logfile.
- See below for details.
-
-
-
- -s scale_factor
-
- Report the specified scale factor in pgbench'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 pgbench_branches table. However, when testing
- custom benchmarks (-f option), the scale factor
- will be reported as 1 unless this option is used.
-
-
-
- -d
-
- Print debugging output.
-
-
-
-
-
-
-
- <application>pgbench</application> common options
-
-
-
- Option
- Description
-
-
-
-
-
- -h hostname
- database server's host
-
-
- -p port
- database server's port
-
-
- -U login
- username to connect as
-
-
-
-
-
-
-
- What is the <quote>transaction</> actually performed in pgbench?
-
-
- The default transaction script issues seven commands per transaction:
-
-
-
- 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;
-
-
-
- If you specify -N, steps 4 and 5 aren't included in the
- transaction. If you specify -S, only the SELECT is
- issued.
-
-
-
-
- Custom Scripts
-
-
- pgbench has support for running custom
- benchmark scenarios by replacing the default transaction script
- (described above) with a transaction script read from a file
- (-f option). In this case a transaction
- counts as one execution of a script file. You can even specify
- multiple scripts (multiple -f options), in which
- case a random one of the scripts is chosen each time a client session
- starts a new transaction.
-
-
-
- The format of a script file is one SQL command per line; multi-line
- SQL commands are not supported. Empty lines and lines beginning with
- -- are ignored. Script file lines can also be
- meta commands, which are interpreted by pgbench
- itself, as described below.
-
-
-
- There is a simple variable-substitution facility for script files.
- Variables can be set by the command-line -D option,
- explained above, or by the meta commands explained below.
- In addition to any variables preset by -D command-line options,
- the variable scale is preset to the current scale factor.
- Once set, a variable's
- value can be inserted into a SQL command by writing
- :variablename. When running more than
- one client session, each session has its own set of variables.
-
-
-
- Script file meta commands begin with a backslash (\).
- Arguments to a meta command are separated by white space.
- These meta commands are supported:
-
-
-
-
-
- \set varname operand1 [ operator operand2 ]
-
-
-
-
- Sets variable varname to a calculated integer value.
- Each operand is either an integer constant or a
- :variablename reference to a variable
- having an integer value. The operator can be
- +, -, *, or /.
-
-
-
- Example:
-
-\set ntellers 10 * :scale
-
-
-
-
-
-
-
- \setrandom varname min max
-
-
-
-
- Sets variable varname to a random integer value
- between the limits min and max inclusive.
- Each limit can be either an integer constant or a
- :variablename reference to a variable
- having an integer value.
-
-
-
- Example:
-
-\setrandom aid 1 :naccounts
-
-
-
-
-
-
-
- \sleep number [ us | ms | s ]
-
-
-
-
- Causes script execution to sleep for the specified duration in
- microseconds (us), milliseconds (ms) or seconds
- (s). If the unit is omitted then seconds are the default.
- number can be either an integer constant or a
- :variablename reference to a variable
- having an integer value.
-
-
-
- Example:
-
-\sleep 10 ms
-
-
-
-
-
-
-
- \setshell varname command [ argument ... ]
-
-
-
-
- Sets variable varname to the result of the shell command
- command. The command must return an integer value
- through its standard output.
-
-
-
- argument can be either a text constant or a
- :variablename reference to a variable of
- any types. If you want to use argument starting with
- colons, you need to add an additional colon at the beginning of
- argument.
-
-
-
- Example:
-
-\setshell variable_to_be_assigned command literal_argument :variable ::literal_starting_with_colon
-
-
-
-
-
-
-
- \shell command [ argument ... ]
-
-
-
-
- Same as \setshell, but the result is ignored.
-
-
-
- Example:
-
-\shell command literal_argument :variable ::literal_starting_with_colon
-
-
-
-
-
-
-
- As an example, the full definition of the built-in TPC-B-like
- transaction is:
-
-
-\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;
-
-
- 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.)
-
-
-
-
-
- Per-transaction logging
-
-
- With the -l option, pgbench writes the time
- taken by each transaction to a logfile. The logfile will be named
- pgbench_log.nnn, where
- nnn is the PID of the pgbench process.
- If the -j option is 2 or higher, creating multiple worker
- threads, each will have its own log file. The first worker will use the
- the same name for its log file as in the standard single worker case.
- The additional log files for the other workers will be named
- pgbench_log.nnn.mmm,
- where mmm is a sequential number for each worker starting
- with 1.
-
-
-
- The format of the log is:
-
-
- client_id transaction_no time file_no time_epoch time_us
-
-
- where time is the elapsed transaction time in microseconds,
- file_no identifies which script file was used
- (useful when multiple scripts were specified with -f),
- and time_epoch/time_us are a
- UNIX epoch format timestamp and an offset
- in microseconds (suitable for creating a ISO 8601
- timestamp with fractional seconds) showing when
- the transaction completed.
-
-
-
- Here are example outputs:
-
- 0 199 2241 0 1175850568 995598
- 0 200 2465 0 1175850568 998079
- 0 201 2513 0 1175850569 608
- 0 202 2038 0 1175850569 2663
-
-
-
-
-
- Good Practices
-
-
- It is very easy to use pgbench to produce completely
- meaningless numbers. Here are some guidelines to help you get useful
- results.
-
-
-
- In the first place, never believe any test that runs
- for only a few seconds. Use the -t or -T 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.
-
-
-
- For the default TPC-B-like test scenario, the initialization scale factor
- (-s) should be at least as large as the largest number of
- clients you intend to test (-c); else you'll mostly be
- measuring update contention. There are only -s rows in
- the pgbench_branches table, and every transaction wants to
- update one of them, so -c values in excess of -s
- will undoubtedly result in lots of transactions blocked waiting for
- other transactions.
-
-
-
- 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.
-
-
-
- A limitation of pgbench is that it can itself become
- the bottleneck when trying to test a large number of client sessions.
- This can be alleviated by running pgbench on a different
- machine from the database server, although low network latency will be
- essential. It might even be useful to run several pgbench
- instances concurrently, on several client machines, against the same
- database server.
-
-
-
-
+
+
+
+ pgbench
+
+
+ pgbench
+
+
+
+ pgbench is a simple program for running benchmark
+ tests on PostgreSQL. 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, pgbench tests a scenario that is
+ loosely based on TPC-B, involving five SELECT,
+ UPDATE, and INSERT commands per transaction.
+ However, it is easy to test other cases by writing your own transaction
+ script files.
+
+
+
+ Typical output from pgbench looks like:
+
+
+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)
+
+
+ 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. The last two lines report the TPS rate,
+ figured with and without counting the time to start database sessions.
+
+
+
+ Overview
+
+
+ The default TPC-B-like transaction test requires specific tables to be
+ set up beforehand. pgbench should be invoked with
+ the -i (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:
+
+
+pgbench -i other-options dbname
+
+
+ where dbname is the name of the already-created
+ database to test in. (You may also need -h,
+ -p, and/or -U options to specify how to
+ connect to the database server.)
+
+
+
+
+ pgbench -i creates four tables pgbench_accounts,
+ pgbench_branches, pgbench_history, and
+ pgbench_tellers,
+ destroying any existing tables of these names.
+ Be very careful to use another database if you have tables having these
+ names!
+
+
+
+
+ At the default scale factor of 1, the tables initially
+ contain this many rows:
+
+
+table # of rows
+---------------------------------
+pgbench_branches 1
+pgbench_tellers 10
+pgbench_accounts 100000
+pgbench_history 0
+
+
+ You can (and, for most purposes, probably should) increase the number
+ of rows by using the -s (scale factor) option. The
+ -F (fillfactor) option might also be used at this point.
+
+
+
+ Once you have done the necessary setup, you can run your benchmark
+ with a command that doesn't include -i, that is
+
+
+pgbench options dbname
+
+
+ In nearly all cases, you'll need some options to make a useful test.
+ The most important options are -c (number of clients),
+ -t (number of transactions), -T (time limit),
+ and -f (specify a custom script file).
+ See below for a full list.
+
+
+
+ shows options that are used
+ during database initialization, while
+ shows options that are used
+ while running benchmarks, and
+ shows options that are useful
+ in both cases.
+
+
+
+ <application>pgbench</application> initialization options
+
+
+
+ Option
+ Description
+
+
+
+
+
+ -i
+
+ Required to invoke initialization mode.
+
+
+
+ -s scale_factor
+
+ Multiply the number of rows generated by the scale factor.
+ For example, -s 100 will create 10,000,000 rows
+ in the pgbench_accounts table. Default is 1.
+
+
+
+ -F fillfactor
+
+ Create the pgbench_accounts,
+ pgbench_tellers and
+ pgbench_branches tables with the given fillfactor.
+ Default is 100.
+
+
+
+
+
+
+
+ <application>pgbench</application> benchmarking options
+
+
+
+ Option
+ Description
+
+
+
+
+
+ -c clients
+
+ Number of clients simulated, that is, number of concurrent database
+ sessions. Default is 1.
+
+
+
+ -j threads
+
+ Number of worker threads within pgbench.
+ 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.
+
+
+
+ -t transactions
+
+ Number of transactions each client runs. Default is 10.
+
+
+
+ -T seconds
+
+ Run the test for this many seconds, rather than a fixed number of
+ transactions per client. -t and
+ -T are mutually exclusive.
+
+
+
+ -M querymode
+
+ Protocol to use for submitting queries to the server:
+
+
+ simple: use simple query protocol.
+
+
+ extended: use extended query protocol.
+
+
+ prepared: use extended query protocol with prepared statements.
+
+
+ The default is simple query protocol. (See
+ for more information.)
+
+
+
+ -N
+
+ Do not update pgbench_tellers and
+ pgbench_branches.
+ This will avoid update contention on these tables, but
+ it makes the test case even less like TPC-B.
+
+
+
+ -S
+
+ Perform select-only transactions instead of TPC-B-like test.
+
+
+
+ -f filename
+
+ Read transaction script from filename.
+ See below for details.
+ -N, -S, and -f
+ are mutually exclusive.
+
+
+
+ -n
+
+ Perform no vacuuming before running the test.
+ This option is necessary
+ if you are running a custom test scenario that does not include
+ the standard tables pgbench_accounts,
+ pgbench_branches, pgbench_history, and
+ pgbench_tellers.
+
+
+
+ -v
+
+ Vacuum all four standard tables before running the test.
+ With neither -n nor -v, pgbench will vacuum the
+ pgbench_tellers and pgbench_branches
+ tables, and will truncate pgbench_history.
+
+
+
+ -D varname=value
+
+ Define a variable for use by a custom script (see below).
+ Multiple -D options are allowed.
+
+
+
+ -C
+
+ Establish a new connection for each transaction, rather than
+ doing it just once per client session.
+ This is useful to measure the connection overhead.
+
+
+
+ -l
+
+ Write the time taken by each transaction to a logfile.
+ See below for details.
+
+
+
+ -s scale_factor
+
+ Report the specified scale factor in pgbench'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 pgbench_branches table. However, when testing
+ custom benchmarks (-f option), the scale factor
+ will be reported as 1 unless this option is used.
+
+
+
+ -d
+
+ Print debugging output.
+
+
+
+
+
+
+
+ <application>pgbench</application> common options
+
+
+
+ Option
+ Description
+
+
+
+
+
+ -h hostname
+ database server's host
+
+
+ -p port
+ database server's port
+
+
+ -U login
+ username to connect as
+
+
+
+
+
+
+
+ What is the <quote>transaction</> actually performed in pgbench?
+
+
+ The default transaction script issues seven commands per transaction:
+
+
+
+ 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;
+
+
+
+ If you specify -N, steps 4 and 5 aren't included in the
+ transaction. If you specify -S, only the SELECT is
+ issued.
+
+
+
+
+ Custom Scripts
+
+
+ pgbench has support for running custom
+ benchmark scenarios by replacing the default transaction script
+ (described above) with a transaction script read from a file
+ (-f option). In this case a transaction
+ counts as one execution of a script file. You can even specify
+ multiple scripts (multiple -f options), in which
+ case a random one of the scripts is chosen each time a client session
+ starts a new transaction.
+
+
+
+ The format of a script file is one SQL command per line; multi-line
+ SQL commands are not supported. Empty lines and lines beginning with
+ -- are ignored. Script file lines can also be
+ meta commands, which are interpreted by pgbench
+ itself, as described below.
+
+
+
+ There is a simple variable-substitution facility for script files.
+ Variables can be set by the command-line -D option,
+ explained above, or by the meta commands explained below.
+ In addition to any variables preset by -D command-line options,
+ the variable scale is preset to the current scale factor.
+ Once set, a variable's
+ value can be inserted into a SQL command by writing
+ :variablename. When running more than
+ one client session, each session has its own set of variables.
+
+
+
+ Script file meta commands begin with a backslash (\).
+ Arguments to a meta command are separated by white space.
+ These meta commands are supported:
+
+
+
+
+
+ \set varname operand1 [ operator operand2 ]
+
+
+
+
+ Sets variable varname to a calculated integer value.
+ Each operand is either an integer constant or a
+ :variablename reference to a variable
+ having an integer value. The operator can be
+ +, -, *, or /.
+
+
+
+ Example:
+
+\set ntellers 10 * :scale
+
+
+
+
+
+
+
+ \setrandom varname min max
+
+
+
+
+ Sets variable varname to a random integer value
+ between the limits min and max inclusive.
+ Each limit can be either an integer constant or a
+ :variablename reference to a variable
+ having an integer value.
+
+
+
+ Example:
+
+\setrandom aid 1 :naccounts
+
+
+
+
+
+
+
+ \sleep number [ us | ms | s ]
+
+
+
+
+ Causes script execution to sleep for the specified duration in
+ microseconds (us), milliseconds (ms) or seconds
+ (s). If the unit is omitted then seconds are the default.
+ number can be either an integer constant or a
+ :variablename reference to a variable
+ having an integer value.
+
+
+
+ Example:
+
+\sleep 10 ms
+
+
+
+
+
+
+
+ \setshell varname command [ argument ... ]
+
+
+
+
+ Sets variable varname to the result of the shell command
+ command. The command must return an integer value
+ through its standard output.
+
+
+
+ argument can be either a text constant or a
+ :variablename reference to a variable of
+ any types. If you want to use argument starting with
+ colons, you need to add an additional colon at the beginning of
+ argument.
+
+
+
+ Example:
+
+\setshell variable_to_be_assigned command literal_argument :variable ::literal_starting_with_colon
+
+
+
+
+
+
+
+ \shell command [ argument ... ]
+
+
+
+
+ Same as \setshell, but the result is ignored.
+
+
+
+ Example:
+
+\shell command literal_argument :variable ::literal_starting_with_colon
+
+
+
+
+
+
+
+ As an example, the full definition of the built-in TPC-B-like
+ transaction is:
+
+
+\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;
+
+
+ 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.)
+
+
+
+
+
+ Per-transaction logging
+
+
+ With the -l option, pgbench writes the time
+ taken by each transaction to a logfile. The logfile will be named
+ pgbench_log.nnn, where
+ nnn is the PID of the pgbench process.
+ If the -j option is 2 or higher, creating multiple worker
+ threads, each will have its own log file. The first worker will use the
+ the same name for its log file as in the standard single worker case.
+ The additional log files for the other workers will be named
+ pgbench_log.nnn.mmm,
+ where mmm is a sequential number for each worker starting
+ with 1.
+
+
+
+ The format of the log is:
+
+
+ client_id transaction_no time file_no time_epoch time_us
+
+
+ where time is the elapsed transaction time in microseconds,
+ file_no identifies which script file was used
+ (useful when multiple scripts were specified with -f),
+ and time_epoch/time_us are a
+ UNIX epoch format timestamp and an offset
+ in microseconds (suitable for creating a ISO 8601
+ timestamp with fractional seconds) showing when
+ the transaction completed.
+
+
+
+ Here are example outputs:
+
+ 0 199 2241 0 1175850568 995598
+ 0 200 2465 0 1175850568 998079
+ 0 201 2513 0 1175850569 608
+ 0 202 2038 0 1175850569 2663
+
+
+
+
+
+ Good Practices
+
+
+ It is very easy to use pgbench to produce completely
+ meaningless numbers. Here are some guidelines to help you get useful
+ results.
+
+
+
+ In the first place, never believe any test that runs
+ for only a few seconds. Use the -t or -T 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.
+
+
+
+ For the default TPC-B-like test scenario, the initialization scale factor
+ (-s) should be at least as large as the largest number of
+ clients you intend to test (-c); else you'll mostly be
+ measuring update contention. There are only -s rows in
+ the pgbench_branches table, and every transaction wants to
+ update one of them, so -c values in excess of -s
+ will undoubtedly result in lots of transactions blocked waiting for
+ other transactions.
+
+
+
+ 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.
+
+
+
+ A limitation of pgbench is that it can itself become
+ the bottleneck when trying to test a large number of client sessions.
+ This can be alleviated by running pgbench on a different
+ machine from the database server, although low network latency will be
+ essential. It might even be useful to run several pgbench
+ instances concurrently, on several client machines, against the same
+ database server.
+
+
+
+