System Administration Functions

Configuration Settings Functions
Server Signaling Functions

The functions described in this section are used to control and monitor a Tacnode installation.

Configuration Settings Functions

Table 8.67 shows the functions available to query and alter run-time configuration parameters.

Table Configuration Settings Functions

Function Description Example(s)

Function Description Example(s)
`current_setting` ( `setting_name` `text` [, `missing_ok` `boolean` ] ) → `text` Returns the current value of the setting `setting_name`. If there is no such setting, `current_setting` throws an error unless `missing_ok` is supplied and is `true` (in which case NULL is returned). This function corresponds to the SQL command SHOW. `current_setting('datestyle')` → `ISO, MDY`
`set_config` ( `setting_name` `text`, `new_value` `text`, `is_local` `boolean` ) → `text` Sets the parameter `setting_name` to `new_value`, and returns that value. If `is_local` is `true`, the new value will only apply during the current transaction. If you want the new value to apply for the rest of the current session, use `false` instead. This function corresponds to the SQL command SET. `set_config('log_statement_stats', 'off', false)` → `off`

current_setting ( setting_name text [, missing_ok boolean ] ) → text

Returns the current value of the setting setting_name. If there is no such setting, current_setting throws an error unless missing_ok is supplied and is true (in which case NULL is returned). This function corresponds to the SQL command SHOW.

current_setting('datestyle') → ISO, MDY

set_config ( setting_name text, new_value text, is_local boolean ) → text

Sets the parameter setting_name to new_value, and returns that value. If is_local is true, the new value will only apply during the current transaction. If you want the new value to apply for the rest of the current session, use false instead. This function corresponds to the SQL command SET.

set_config('log_statement_stats', 'off', false) → off

Server Signaling Functions

The functions shown in Table 8.68 send control signals to other server processes. Use of these functions is restricted to superusers by default but access may be granted to others using GRANT, with noted exceptions.

Each of these functions returns true if the signal was successfully sent and false if sending the signal failed.

Table Server Signaling Functions

Function Description

Function Description
`pg_cancel_backend` ( `pid` `integer` ) → `boolean` Cancels the current query of the session whose backend process has the specified process ID. This is also allowed if the calling role is a member of the role whose backend is being canceled or the calling role has been granted `pg_signal_backend`, however only superusers can cancel superuser backends.
`pg_terminate_backend` ( `pid` `integer`, `timeout` `bigint` `DEFAULT` `0` ) → `boolean` Terminates the session whose backend process has the specified process ID. This is also allowed if the calling role is a member of the role whose backend is being terminated or the calling role has been granted `pg_signal_backend`, however only superusers can terminate superuser backends. If `timeout` is not specified or zero, this function returns `true` whether the process actually terminates or not, indicating only that the sending of the signal was successful. If the `timeout` is specified (in milliseconds) and greater than zero, the function waits until the process is actually terminated or until the given time has passed. If the process is terminated, the function returns `true`. On timeout, a warning is emitted and `false` is returned.

pg_cancel_backend ( pid integer ) → boolean

Cancels the current query of the session whose backend process has the specified process ID. This is also allowed if the calling role is a member of the role whose backend is being canceled or the calling role has been granted pg_signal_backend, however only superusers can cancel superuser backends.

pg_terminate_backend ( pid integer, timeout bigint DEFAULT 0 ) → boolean

Terminates the session whose backend process has the specified process ID. This is also allowed if the calling role is a member of the role whose backend is being terminated or the calling role has been granted pg_signal_backend, however only superusers can terminate superuser backends.

If timeout is not specified or zero, this function returns true whether the process actually terminates or not, indicating only that the sending of the signal was successful. If the timeout is specified (in milliseconds) and greater than zero, the function waits until the process is actually terminated or until the given time has passed. If the process is terminated, the function returns true. On timeout, a warning is emitted and false is returned.

pg_cancel_backend and pg_terminate_backend send signals (SIGINT or SIGTERM respectively) to backend processes identified by process ID. The process ID of an active backend can be found from the pid column of the pg_stat_activity view, or by listing the postgres processes on the server (using ps on Unix or the Task Manager on Windows). The role of an active backend can be found from the usename column of the pg_stat_activity view.

System Administration Functions