sys_get_config

Description

Returns the value for the requested variable using the following logic:

1. If the option exists in sys.sys_config return the value from there.
2. Else fall back on the provided default value.

Notes for using sys_get_config():

• If the default value argument to sys_get_config() is NULL and case 2. is reached, NULL is returned. It is then expected that the caller is able to handle NULL for the given configuration option.
• The convention is to name the user variables @sys.. It is that is stored in the sys_config table and is what is expected as the argument to sys_get_config().
• If you want to check whether the configuration option has already been set and if not assign with the return value of sys_get_config() you can use IFNULL(…) (see example below). However this should not be done inside a loop (e.g. for each row in a result set) as for repeated calls where assignment is only needed in the first iteration using IFNULL(…) is expected to be significantly slower than using an IF (…) THEN … END IF; block (see example below).

Parameters

in_variable_name (VARCHAR(128)): The name of the config option to return the value for.

in_default_value (VARCHAR(128)): The default value to return if the variable does not exist in sys.sys_config.

Returns

VARCHAR(128)

Example

– Get the configuration value from sys.sys_config falling back on 128 if the option is not present in the table. mysql> SELECT sys.sys_get_config(‘statement_truncate_len’, 128) AS Value; +——-+ | Value | +——-+ | 64 | +——-+ 1 row in set (0.00 sec)

– Check whether the option is already set, if not assign - IFNULL(…) one liner example. mysql> SET @sys.statement_truncate_len = IFNULL(@sys.statement_truncate_len, sys.sys_get_config(‘statement_truncate_len’, 64)); Query OK, 0 rows affected (0.00 sec)

– Check whether the option is already set, if not assign - IF … THEN … END IF example. IF (@sys.statement_truncate_len IS NULL) THEN SET @sys.statement_truncate_len = sys.sys_get_config(‘statement_truncate_len’, 64); END IF;