6.5.7 mysqlslap — A Load Emulation Client

mysqlslap is a diagnostic program designed to emulate client load for a MySQL server and to report the timing of each stage. It works as if multiple clients are accessing the server.

Invoke mysqlslap like this:

mysqlslap [options]

Some options such as --create or --query enable you to specify a string containing an SQL statement or a file containing statements. If you specify a file, by default it must contain one statement per line. (That is, the implicit statement delimiter is the newline character.) Use the --delimiter option to specify a different delimiter, which enables you to specify statements that span multiple lines or place multiple statements on a single line. You cannot include comments in a file; mysqlslap does not understand them.

mysqlslap runs in three stages:

1. Create schema, table, and optionally any stored programs or data to use for the test. This stage uses a single client connection.

2. Run the load test. This stage can use many client connections.

3. Clean up (disconnect, drop table if specified). This stage uses a single client connection.

Examples:

Supply your own create and query SQL statements, with 50 clients querying and 200 selects for each (enter the command on a single line):

mysqlslap --delimiter=";"
  --create="CREATE TABLE a (b int);INSERT INTO a VALUES (23)"
  --query="SELECT * FROM a" --concurrency=50 --iterations=200

Let mysqlslap build the query SQL statement with a table of two INT columns and three VARCHAR columns. Use five clients querying 20 times each. Do not create the table or insert the data (that is, use the previous test's schema and data):

mysqlslap --concurrency=5 --iterations=20
  --number-int-cols=2 --number-char-cols=3
  --auto-generate-sql

Tell the program to load the create, insert, and query SQL statements from the specified files, where the create.sql file has multiple table creation statements delimited by ';' and multiple insert statements delimited by ';'. The --query file should contain multiple queries delimited by ';'. Run all the load statements, then run all the queries in the query file with five clients (five times each):

mysqlslap --concurrency=5
  --iterations=5 --query=query.sql --create=create.sql
  --delimiter=";"

mysqlslap supports the following options, which can be specified on the command line or in the [mysqlslap] and [client] groups of an option file. For information about option files used by MySQL programs, see Section 6.2.2.2, “Using Option Files”.

Table 6.16 mysqlslap Options

Option Name	Description
--auto-generate-sql	Generate SQL statements automatically when they are not supplied in files or using command options
--auto-generate-sql-add-autoincrement	Add AUTO_INCREMENT column to automatically generated tables
--auto-generate-sql-execute-number	Specify how many queries to generate automatically
--auto-generate-sql-guid-primary	Add a GUID-based primary key to automatically generated tables
--auto-generate-sql-load-type	Specify the test load type
--auto-generate-sql-secondary-indexes	Specify how many secondary indexes to add to automatically generated tables
--auto-generate-sql-unique-query-number	How many different queries to generate for automatic tests
--auto-generate-sql-unique-write-number	How many different queries to generate for --auto-generate-sql-write-number
--auto-generate-sql-write-number	How many row inserts to perform on each thread
--commit	How many statements to execute before committing
--compress	Compress all information sent between client and server
--compression-algorithms	Permitted compression algorithms for connections to server
--concurrency	Number of clients to simulate when issuing the SELECT statement
--create	File or string containing the statement to use for creating the table
--create-schema	Schema in which to run the tests
--csv	Generate output in comma-separated values format
--debug	Write debugging log
--debug-check	Print debugging information when program exits
--debug-info	Print debugging information, memory, and CPU statistics when program exits
--defaults-extra-file	Read named option file in addition to usual option files
--defaults-file	Read only named option file
--defaults-group-suffix	Option group suffix value
--delimiter	Delimiter to use in SQL statements
--detach	Detach (close and reopen) each connection after each N statements
--enable-cleartext-plugin	Enable cleartext authentication plugin
--engine	Storage engine to use for creating the table
--get-server-public-key	Request RSA public key from server
--help	Display help message and exit
--host	Host on which MySQL server is located
--iterations	Number of times to run the tests
--login-path	Read login path options from .mylogin.cnf
--no-defaults	Read no option files
--no-drop	Do not drop any schema created during the test run
--no-login-paths	Do not read login paths from the login path file
--number-char-cols	Number of VARCHAR columns to use if --auto-generate-sql is specified
--number-int-cols	Number of INT columns to use if --auto-generate-sql is specified
--number-of-queries	Limit each client to approximately this number of queries
--only-print	Do not connect to databases. mysqlslap only prints what it would have done
--password	Password to use when connecting to server
--password1	First multifactor authentication password to use when connecting to server
--password2	Second multifactor authentication password to use when connecting to server
--password3	Third multifactor authentication password to use when connecting to server
--pipe	Connect to server using named pipe (Windows only)
--port	TCP/IP port number for connection
--post-query	File or string containing the statement to execute after the tests have completed
--post-system	String to execute using system() after the tests have completed
--pre-query	File or string containing the statement to execute before running the tests
--pre-system	String to execute using system() before running the tests
--print-defaults	Print default options
--protocol	Transport protocol to use
--query	File or string containing the SELECT statement to use for retrieving data
--server-public-key-path	Path name to file containing RSA public key
--shared-memory-base-name	Shared-memory name for shared-memory connections (Windows only)
--silent	Silent mode
--socket	Unix socket file or Windows named pipe to use
--sql-mode	Set SQL mode for client session
--ssl-ca	File that contains list of trusted SSL Certificate Authorities
--ssl-capath	Directory that contains trusted SSL Certificate Authority certificate files
--ssl-cert	File that contains X.509 certificate
--ssl-cipher	Permissible ciphers for connection encryption
--ssl-fips-mode	Whether to enable FIPS mode on client side
--ssl-key	File that contains X.509 key
--ssl-mode	Desired security state of connection to server
--ssl-session-data	File that contains SSL session data
--ssl-session-data-continue-on-failed-reuse	Whether to establish connections if session reuse fails
--tls-ciphersuites	Permissible TLSv1.3 ciphersuites for encrypted connections
--tls-sni-servername	Server name supplied by the client
--tls-version	Permissible TLS protocols for encrypted connections
--user	MySQL user name to use when connecting to server
--verbose	Verbose mode
--version	Display version information and exit
--zstd-compression-level	Compression level for connections to server that use zstd compression

• --help, -?

  Command-Line Format	--help

  Display a help message and exit.

• --auto-generate-sql, -a

  Command-Line Format	--auto-generate-sql
  Type	Boolean
  Default Value	FALSE

  Generate SQL statements automatically when they are not supplied in files or using command options.

• --auto-generate-sql-add-autoincrement

  Command-Line Format	--auto-generate-sql-add-autoincrement
  Type	Boolean
  Default Value	FALSE

  Add an AUTO_INCREMENT column to automatically generated tables.

• --auto-generate-sql-execute-number=N

  Command-Line Format	--auto-generate-sql-execute-number=#
  Type	Numeric

  Specify how many queries to generate automatically.

• --auto-generate-sql-guid-primary

  Command-Line Format	--auto-generate-sql-guid-primary
  Type	Boolean
  Default Value	FALSE

  Add a GUID-based primary key to automatically generated tables.

• --auto-generate-sql-load-type=type

  Command-Line Format	--auto-generate-sql-load-type=type
  Type	Enumeration
  Default Value	mixed
  Valid Values	read write key update mixed

  Specify the test load type. The permissible values are read (scan tables), write (insert into tables), key (read primary keys), update (update primary keys), or mixed (half inserts, half scanning selects). The default is mixed.

• --auto-generate-sql-secondary-indexes=N

  Command-Line Format	--auto-generate-sql-secondary-indexes=#
  Type	Numeric
  Default Value	0

  Specify how many secondary indexes to add to automatically generated tables. By default, none are added.

• --auto-generate-sql-unique-query-number=N

  Command-Line Format	--auto-generate-sql-unique-query-number=#
  Type	Numeric
  Default Value	10

  How many different queries to generate for automatic tests. For example, if you run a key test that performs 1000 selects, you can use this option with a value of 1000 to run 1000 unique queries, or with a value of 50 to perform 50 different selects. The default is 10.

• --auto-generate-sql-unique-write-number=N

  Command-Line Format	--auto-generate-sql-unique-write-number=#
  Type	Numeric
  Default Value	10

  How many different queries to generate for --auto-generate-sql-write-number. The default is 10.

• --auto-generate-sql-write-number=N

  Command-Line Format	--auto-generate-sql-write-number=#
  Type	Numeric
  Default Value	100

  How many row inserts to perform. The default is 100.

• --commit=N

  Command-Line Format	--commit=#
  Type	Numeric
  Default Value	0

  How many statements to execute before committing. The default is 0 (no commits are done).

• --compress, -C

  Command-Line Format	--compress[={OFF|ON}]
  Deprecated	Yes
  Type	Boolean
  Default Value	OFF

  Compress all information sent between the client and the server if possible. See Section 6.2.8, “Connection Compression Control”.

  This option is deprecated. Expect it to be removed in a future version of MySQL. See Configuring Legacy Connection Compression.

• --compression-algorithms=value

  Command-Line Format	--compression-algorithms=value
  Type	Set
  Default Value	uncompressed
  Valid Values	zlib zstd uncompressed

  The permitted compression algorithms for connections to the server. The available algorithms are the same as for the protocol_compression_algorithms system variable. The default value is uncompressed.

  For more information, see Section 6.2.8, “Connection Compression Control”.

• --concurrency=N, -c N

  Command-Line Format	--concurrency=#
  Type	Numeric

  The number of parallel clients to simulate.

• --create=value

  Command-Line Format	--create=value
  Type	String

  The file or string containing the statement to use for creating the table.

• --create-schema=value

  Command-Line Format	--create-schema=value
  Type	String

  The schema in which to run the tests.

  Note

  If the --auto-generate-sql option is also given, mysqlslap drops the schema at the end of the test run. To avoid this, use the --no-drop option as well.

• --csv[=file_name]

  Command-Line Format	--csv=[file]
  Type	File name

  Generate output in comma-separated values format. The output goes to the named file, or to the standard output if no file is given.

• --debug[=debug_options], -# [debug_options]

  Command-Line Format	--debug[=debug_options]
  Type	String
  Default Value	d:t:o,/tmp/mysqlslap.trace

  Write a debugging log. A typical debug_options string is d:t:o,file_name. The default is d:t:o,/tmp/mysqlslap.trace.

  This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by Oracle are not built using this option.

• --debug-check

  Command-Line Format	--debug-check
  Type	Boolean
  Default Value	FALSE

  Print some debugging information when the program exits.

  This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by Oracle are not built using this option.

• --debug-info, -T

  Command-Line Format	--debug-info
  Type	Boolean
  Default Value	FALSE

  Print debugging information and memory and CPU usage statistics when the program exits.

  This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by Oracle are not built using this option.

• --default-auth=plugin

  Command-Line Format	--default-auth=plugin
  Type	String

  A hint about which client-side authentication plugin to use. See Section 8.2.17, “Pluggable Authentication”.

• --defaults-extra-file=file_name

  Command-Line Format	--defaults-extra-file=file_name
  Type	File name

  Read this option file after the global option file but (on Unix) before the user option file. If the file does not exist or is otherwise inaccessible, an error occurs. If file_name is not an absolute path name, it is interpreted relative to the current directory.

  For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.

• --defaults-file=file_name

  Command-Line Format	--defaults-file=file_name
  Type	File name

  Use only the given option file. If the file does not exist or is otherwise inaccessible, an error occurs. If file_name is not an absolute path name, it is interpreted relative to the current directory.

  Exception: Even with --defaults-file, client programs read .mylogin.cnf.

  For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.

• --defaults-group-suffix=str

  Command-Line Format	--defaults-group-suffix=str
  Type	String

  Read not only the usual option groups, but also groups with the usual names and a suffix of str. For example, mysqlslap normally reads the [client] and [mysqlslap] groups. If this option is given as --defaults-group-suffix=_other, mysqlslap also reads the [client_other] and [mysqlslap_other] groups.

  For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.

• --delimiter=str, -F str

  Command-Line Format	--delimiter=str
  Type	String

  The delimiter to use in SQL statements supplied in files or using command options.

• --detach=N

  Command-Line Format	--detach=#
  Type	Numeric
  Default Value	0

  Detach (close and reopen) each connection after each N statements. The default is 0 (connections are not detached).

• --enable-cleartext-plugin

  Command-Line Format	--enable-cleartext-plugin
  Type	Boolean
  Default Value	FALSE

  Enable the mysql_clear_password cleartext authentication plugin. (See Section 8.4.1.3, “Client-Side Cleartext Pluggable Authentication”.)

• --engine=engine_name, -e engine_name

  Command-Line Format	--engine=engine_name
  Type	String

  The storage engine to use for creating tables.

• --get-server-public-key

  Command-Line Format	--get-server-public-key
  Type	Boolean

  Request from the server the RSA public key that it uses for key pair-based password exchange. This option applies to clients that connect to the server using an account that authenticates with the caching_sha2_password authentication plugin. For connections by such accounts, the server does not send the public key to the client unless requested. The option is ignored for accounts that do not authenticate with that plugin. It is also ignored if RSA-based password exchange is not needed, as is the case when the client connects to the server using a secure connection.

  If --server-public-key-path=file_name is given and specifies a valid public key file, it takes precedence over --get-server-public-key.

  For information about the caching_sha2_password plugin, see Section 8.4.1.1, “Caching SHA-2 Pluggable Authentication”.

• --host=host_name, -h host_name

  Command-Line Format	--host=host_name
  Type	String
  Default Value	localhost

  Connect to the MySQL server on the given host.

• --iterations=N, -i N

  Command-Line Format	--iterations=#
  Type	Numeric

  The number of times to run the tests.

• --login-path=name

  Command-Line Format	--login-path=name
  Type	String

  Read options from the named login path in the .mylogin.cnf login path file. A “login path” is an option group containing options that specify which MySQL server to connect to and which account to authenticate as. To create or modify a login path file, use the mysql_config_editor utility. See Section 6.6.7, “mysql_config_editor — MySQL Configuration Utility”.

  For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.

• --no-login-paths

  Command-Line Format	--no-login-paths

  Skips reading options from the login path file.

  See --login-path for related information.

  For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.

• --no-drop

  Command-Line Format	--no-drop
  Type	Boolean
  Default Value	FALSE

  Prevent mysqlslap from dropping any schema it creates during the test run.

• --no-defaults

  Command-Line Format	--no-defaults

  Do not read any option files. If program startup fails due to reading unknown options from an option file, --no-defaults can be used to prevent them from being read.

  The exception is that the .mylogin.cnf file is read in all cases, if it exists. This permits passwords to be specified in a safer way than on the command line even when --no-defaults is used. To create .mylogin.cnf, use the mysql_config_editor utility. See Section 6.6.7, “mysql_config_editor — MySQL Configuration Utility”.

  For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.

• --number-char-cols=N, -x N

  Command-Line Format	--number-char-cols=#
  Type	Numeric

  The number of VARCHAR columns to use if --auto-generate-sql is specified.

• --number-int-cols=N, -y N

  Command-Line Format	--number-int-cols=#
  Type	Numeric

  The number of INT columns to use if --auto-generate-sql is specified.

• --number-of-queries=N

  Command-Line Format	--number-of-queries=#
  Type	Numeric

  Limit each client to approximately this many queries. Query counting takes into account the statement delimiter. For example, if you invoke mysqlslap as follows, the ; delimiter is recognized so that each instance of the query string counts as two queries. As a result, 5 rows (not 10) are inserted.

  mysqlslap --delimiter=";" --number-of-queries=10
            --query="use test;insert into t values(null)"

• --only-print

  Command-Line Format	--only-print
  Type	Boolean
  Default Value	FALSE

  Do not connect to databases. mysqlslap only prints what it would have done.

• --password[=password], -p[password]

  Command-Line Format	--password[=password]
  Type	String

  The password of the MySQL account used for connecting to the server. The password value is optional. If not given, mysqlslap prompts for one. If given, there must be no space between --password= or -p and the password following it. If no password option is specified, the default is to send no password.

  Specifying a password on the command line should be considered insecure. To avoid giving the password on the command line, use an option file. See Section 8.1.2.1, “End-User Guidelines for Password Security”.

  To explicitly specify that there is no password and that mysqlslap should not prompt for one, use the --skip-password option.

• --password1[=pass_val]

  The password for multifactor authentication factor 1 of the MySQL account used for connecting to the server. The password value is optional. If not given, mysqlslap prompts for one. If given, there must be no space between --password1= and the password following it. If no password option is specified, the default is to send no password.

  Specifying a password on the command line should be considered insecure. To avoid giving the password on the command line, use an option file. See Section 8.1.2.1, “End-User Guidelines for Password Security”.

  To explicitly specify that there is no password and that mysqlslap should not prompt for one, use the --skip-password1 option.

  --password1 and --password are synonymous, as are --skip-password1 and --skip-password.

• --password2[=pass_val]

  The password for multifactor authentication factor 2 of the MySQL account used for connecting to the server. The semantics of this option are similar to the semantics for --password1; see the description of that option for details.

• --password3[=pass_val]

  The password for multifactor authentication factor 3 of the MySQL account used for connecting to the server. The semantics of this option are similar to the semantics for --password1; see the description of that option for details.

• --pipe, -W

  Command-Line Format	--pipe
  Type	String

  On Windows, connect to the server using a named pipe. This option applies only if the server was started with the named_pipe system variable enabled to support named-pipe connections. In addition, the user making the connection must be a member of the Windows group specified by the named_pipe_full_access_group system variable.

• --plugin-dir=dir_name

  Command-Line Format	--plugin-dir=dir_name
  Type	Directory name

  The directory in which to look for plugins. Specify this option if the --default-auth option is used to specify an authentication plugin but mysqlslap does not find it. See Section 8.2.17, “Pluggable Authentication”.

• --port=port_num, -P port_num

  Command-Line Format	--port=port_num
  Type	Numeric
  Default Value	3306

  For TCP/IP connections, the port number to use.

• --post-query=value

  Command-Line Format	--post-query=value
  Type	String

  The file or string containing the statement to execute after the tests have completed. This execution is not counted for timing purposes.

• --post-system=str

  Command-Line Format	--post-system=str
  Type	String

  The string to execute using system() after the tests have completed. This execution is not counted for timing purposes.

• --pre-query=value

  Command-Line Format	--pre-query=value
  Type	String

  The file or string containing the statement to execute before running the tests. This execution is not counted for timing purposes.

• --pre-system=str

  Command-Line Format	--pre-system=str
  Type	String

  The string to execute using system() before running the tests. This execution is not counted for timing purposes.

• --print-defaults

  Command-Line Format	--print-defaults

  Print the program name and all options that it gets from option files.

  For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”.

• --protocol={TCP|SOCKET|PIPE|MEMORY}

  Command-Line Format	--protocol=type
  Type	String
  Default Value	[see text]
  Valid Values	TCP SOCKET PIPE MEMORY

  The transport protocol to use for connecting to the server. It is useful when the other connection parameters normally result in use of a protocol other than the one you want. For details on the permissible values, see Section 6.2.7, “Connection Transport Protocols”.

• --query=value, -q value

  Command-Line Format	--query=value
  Type	String

  The file or string containing the SELECT statement to use for retrieving data.

• --server-public-key-path=file_name

  Command-Line Format	--server-public-key-path=file_name
  Type	File name

  The path name to a file in PEM format containing a client-side copy of the public key required by the server for RSA key pair-based password exchange. This option applies to clients that authenticate with the sha256_password or caching_sha2_password authentication plugin. This option is ignored for accounts that do not authenticate with one of those plugins. It is also ignored if RSA-based password exchange is not used, as is the case when the client connects to the server using a secure connection.

  If --server-public-key-path=file_name is given and specifies a valid public key file, it takes precedence over --get-server-public-key.

  For sha256_password, this option applies only if MySQL was built using OpenSSL.

  For information about the sha256_password and caching_sha2_password plugins, see Section 8.4.1.2, “SHA-256 Pluggable Authentication”, and Section 8.4.1.1, “Caching SHA-2 Pluggable Authentication”.

• --shared-memory-base-name=name

  Command-Line Format	--shared-memory-base-name=name
  Platform Specific	Windows

  On Windows, the shared-memory name to use for connections made using shared memory to a local server. The default value is MYSQL. The shared-memory name is case-sensitive.

  This option applies only if the server was started with the shared_memory system variable enabled to support shared-memory connections.

• --silent, -s

  Command-Line Format	--silent

  Silent mode. No output.

• --socket=path, -S path

  Command-Line Format	--socket={file_name|pipe_name}
  Type	String

  For connections to localhost, the Unix socket file to use, or, on Windows, the name of the named pipe to use.

  On Windows, this option applies only if the server was started with the named_pipe system variable enabled to support named-pipe connections. In addition, the user making the connection must be a member of the Windows group specified by the named_pipe_full_access_group system variable.

• --sql-mode=mode

  Command-Line Format	--sql-mode=mode
  Type	String

  Set the SQL mode for the client session.

• --ssl*

  Options that begin with --ssl specify whether to connect to the server using encryption and indicate where to find SSL keys and certificates. See Command Options for Encrypted Connections.

• --ssl-fips-mode={OFF|ON|STRICT}

  Command-Line Format	--ssl-fips-mode={OFF|ON|STRICT}
  Deprecated	Yes
  Type	Enumeration
  Default Value	OFF
  Valid Values	OFF ON STRICT

  Controls whether to enable FIPS mode on the client side. The --ssl-fips-mode option differs from other --ssl-xxx options in that it is not used to establish encrypted connections, but rather to affect which cryptographic operations to permit. See Section 8.8, “FIPS Support”.

  These --ssl-fips-mode values are permitted:

  • OFF: Disable FIPS mode.

  • ON: Enable FIPS mode.

  • STRICT: Enable “strict” FIPS mode.

  Note

  If the OpenSSL FIPS Object Module is not available, the only permitted value for --ssl-fips-mode is OFF. In this case, setting --ssl-fips-mode to ON or STRICT causes the client to produce a warning at startup and to operate in non-FIPS mode.

  This option is deprecated. Expect it to be removed in a future version of MySQL.

• --tls-ciphersuites=ciphersuite_list

  Command-Line Format	--tls-ciphersuites=ciphersuite_list
  Type	String

  The permissible ciphersuites for encrypted connections that use TLSv1.3. The value is a list of one or more colon-separated ciphersuite names. The ciphersuites that can be named for this option depend on the SSL library used to compile MySQL. For details, see Section 8.3.2, “Encrypted Connection TLS Protocols and Ciphers”.

• --tls-sni-servername=server_name

  Command-Line Format	--tls-sni-servername=server_name
  Type	String

  When specified, the name is passed to the libmysqlclient C API library using the MYSQL_OPT_TLS_SNI_SERVERNAME option of mysql_options(). The server name is not case-sensitive. To show which server name the client specified for the current session, if any, check the Tls_sni_server_name status variable.

  Server Name Indication (SNI) is an extension to the TLS protocol (OpenSSL must be compiled using TLS extensions for this option to function). The MySQL implementation of SNI represents the client-side only.

• --tls-version=protocol_list

  Command-Line Format	--tls-version=protocol_list
  Type	String
  Default Value	TLSv1,TLSv1.1,TLSv1.2,TLSv1.3 (OpenSSL 1.1.1 or higher) TLSv1,TLSv1.1,TLSv1.2 (otherwise)

  The permissible TLS protocols for encrypted connections. The value is a list of one or more comma-separated protocol names. The protocols that can be named for this option depend on the SSL library used to compile MySQL. For details, see Section 8.3.2, “Encrypted Connection TLS Protocols and Ciphers”.

• --user=user_name, -u user_name

  Command-Line Format	--user=user_name,
  Type	String

  The user name of the MySQL account to use for connecting to the server.

• --verbose, -v

  Command-Line Format	--verbose

  Verbose mode. Print more information about what the program does. This option can be used multiple times to increase the amount of information.

• --version, -V

  Command-Line Format	--version

  Display version information and exit.

• --zstd-compression-level=level

  Command-Line Format	--zstd-compression-level=#
  Type	Integer

  The compression level to use for connections to the server that use the zstd compression algorithm. The permitted levels are from 1 to 22, with larger values indicating increasing levels of compression. The default zstd compression level is 3. The compression level setting has no effect on connections that do not use zstd compression.

  For more information, see Section 6.2.8, “Connection Compression Control”.