Specifies the name of the database to test in. If this is not specified, the environment variable LTDATABASE is used. If that is not set, the user name specified for the connection is used.

Required to invoke initialization mode.

Perform just a selected set of the normal initialization steps. init_steps specifies the initialization steps to be performed, using one character per step. Each step is invoked in the specified order. The default is dtgvp. The available steps are:

Create the ltbench_accounts, ltbench_tellers and ltbench_branches tables with the given fillfactor. Default is 100.

Perform no vacuuming during initialization. (This option suppresses the v initialization step, even if it was specified in -I.)

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).

This setting has no effect if G is specified in -I.

Multiply the number of rows generated by the scale factor. For example, -s 100 will create 10,000,000 rows in the ltbench_accounts table. Default is 1. When the scale is 20,000 or larger, the columns used to hold account identifiers (aid columns) will switch to using larger integers (bigint), in order to be big enough to hold the range of account identifiers.

Create foreign key constraints between the standard tables. (This option adds the f step to the initialization step sequence, if it is not already present.)

Create indexes in the specified tablespace, rather than the default tablespace.

Create a partitioned ltbench_accounts table with NAME method. Expected values are range or hash. This option requires that --partitions is set to non-zero. If unspecified, default is range.

Create a partitioned ltbench_accounts table with NUM partitions of nearly equal size for the scaled number of accounts. Default is 0, meaning no partitioning.

Create tables in the specified tablespace, rather than the default tablespace.

Create all tables as unlogged tables, rather than permanent tables.

Add the specified built-in script to the list of scripts to be executed. Available built-in scripts are: tpcb-like, simple-update and select-only. Unambiguous prefixes of built-in names are accepted. With the special name list, show the list of built-in scripts and exit immediately.

Optionally, write an integer weight after @ to adjust the probability of selecting this script versus other ones. The default weight is 1. See below for details.

Number of clients simulated, that is, number of concurrent database sessions. Default is 1.

Establish a new connection for each transaction, rather than doing it just once per client session. This is useful to measure the connection overhead.

Print debugging output.

Define a variable for use by a custom script (see below). Multiple -D options are allowed.

Add a transaction script read from filename to the list of scripts to be executed.

Optionally, write an integer weight after @ 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 @ character, append a weight so that there is no ambiguity, for example filen@me@1.) See below for details.

Number of worker threads within ltbench. 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.

Write information about each transaction to a log file. See below for details.

Transactions that last more than limit milliseconds are counted and reported separately, as late.

When throttling is used (--rate=...), transactions that lag behind schedule by more than limit 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 skipped.

Protocol to use for submitting queries to the server:

In the prepared mode, ltbench reuses the parse analysis result starting from the second query iteration, so ltbench runs faster than in other modes.

The default is simple query protocol. (See Chapter 49 for more information.)

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 ltbench_accounts, ltbench_branches, ltbench_history, and ltbench_tellers.

Run built-in simple-update script. Shorthand for -b simple-update.

Show progress report every sec 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 (-R), 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.

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.

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.

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.

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.

If --latency-limit is used together with --rate, 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.

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.

Report the specified scale factor in ltbench'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 ltbench_branches table. However, when testing only custom benchmarks (-f option), the scale factor will be reported as 1 unless this option is used.

Run built-in select-only script. Shorthand for -b select-only.

Number of transactions each client runs. Default is 10.

Run the test for this many seconds, rather than a fixed number of transactions per client. -t and -T are mutually exclusive.

Vacuum all four standard tables before running the test. With neither -n nor -v, ltbench will vacuum the ltbench_tellers and ltbench_branches tables, and will truncate ltbench_history.

Length of aggregation interval (in seconds). May be used only with -l option. With this option, the log contains per-interval summary data, as described below.

Set the filename prefix for the log files created by --log. The default is ltbench_log.

When showing progress (option -P), 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.

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 seed may be: time (the default, the seed is based on the current time), rand (use a strong random source, failing if none is available), or an unsigned decimal integer value. The random generator is invoked explicitly from a ltbench script (random... functions) or implicitly (for instance option --rate uses it to schedule transactions). When explicitly set, the value used for seeding is shown on the terminal. Any value allowed for seed may also be provided through the environment variable LTBENCH_RANDOM_SEED. To ensure that the provided seed impacts all possible uses, put this option first or use the environment variable.

Setting the seed explicitly allows to reproduce a ltbench run exactly, as far as random numbers are concerned. As the random state is managed per thread, this means the exact same ltbench 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.

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.

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).

Show the actual code of builtin script scriptname on stderr, and exit immediately.

The database server's host name

The database server's port number

The user name to connect as

Print the ltbench version and exit.

Show help about ltbench command line arguments, and exit.

These commands may be used to end SQL queries, taking the place of the terminating semicolon (;).

When the \gset 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 prefix if provided.

When the \aset command is used, all combined SQL queries (separated by \;) have their columns stored into variables named after column names, and prefixed with prefix 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.

The following example puts the final account balance from the first query into variable abalance, and fills variables p_two and p_three 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 four and five.

UPDATE ltbench_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

This group of commands implements nestable conditional blocks, similarly to ltsql's \if expression. Conditional expressions are identical to those with \set, with non-zero values interpreted as true.

Sets variable varname to a value calculated from expression. The expression may contain the NULL constant, Boolean constants TRUE and FALSE, integer constants such as 5432, double constants such as 3.14159, references to variables :variablename, operators with their usual SQL precedence and associativity, function calls, SQL CASE generic conditional expressions and parentheses.

Functions and most operators return NULL on NULL input.

For conditional purposes, non zero numerical values are TRUE, zero numerical values and NULL are FALSE.

Too large or small integer and double constants, as well as integer arithmetic operators (+, -, * and /) raise errors on overflows.

When no final ELSE clause is provided to a CASE, the default value is NULL.

Examples:

\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

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

Sets variable varname to the result of the shell command command with the given argument(s). The command must return an integer value through its standard output.

command and each argument can be either a text constant or a :variablename reference to a variable. If you want to use an argument starting with a colon, write an additional colon at the beginning of argument.

Example:

\setshell variable_to_be_assigned command literal_argument :variable ::literal_starting_with_colon

Same as \setshell, but the result of the command is discarded.

Example:

\shell command literal_argument :variable ::literal_starting_with_colon