| PostgreSQL 8.0.23 Documentation | ||||
|---|---|---|---|---|
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Table 9-44 shows the functions available to query and alter run-time configuration parameters.
Table 9-44. Configuration Settings Functions
| Name | Return Type | Description | 
|---|---|---|
| current_setting(setting_name) | text | current value of setting | 
| set_config(setting_name,
                             new_value,
                             is_local) | text | set parameter and return new value | 
    The function current_setting yields the
    current value of the setting setting_name.
    It corresponds to the SQL command
    SHOW.  An example:
SELECT current_setting('datestyle');
 current_setting
-----------------
 ISO, MDY
(1 row)
    set_config sets the parameter
    setting_name to
    new_value.  If
    is_local is true, the
    new value will only apply to the current transaction. If you want
    the new value to apply for the current session, use
    false instead. The function corresponds to the
    SQL command SET. An example:
SELECT set_config('log_statement_stats', 'off', false);
 set_config
------------
 off
(1 row)
The function shown in Table 9-45 sends control signals to other server processes. Use of this function is restricted to superusers.
Table 9-45. Backend Signalling Functions
| Name | Return Type | Description | 
|---|---|---|
| pg_cancel_backend(pid) | int | Cancel a backend's current query | 
This function returns 1 if successful, 0 if not successful. The process ID (pid) of an active backend can be found from the procpid column in the pg_stat_activity view, or by listing the postgres processes on the server with ps.
The functions shown in Table 9-46 assist in making on-line backups. Use of these functions is restricted to superusers.
Table 9-46. Backup Control Functions
| Name | Return Type | Description | 
|---|---|---|
| pg_start_backup(label_text) | text | Set up for performing on-line backup | 
| pg_stop_backup() | text | Finish performing on-line backup | 
    pg_start_backup accepts a single parameter which is an
    arbitrary user-defined label for the backup.  (Typically this would be
    the name under which the backup dump file will be stored.)  The function
    writes a backup label file into the database cluster's data directory,
    and then returns the backup's starting WAL offset as text.  (The user
    need not pay any attention to this result value, but it is provided in
    case it is of use.)
   
    pg_stop_backup removes the label file created by
    pg_start_backup, and instead creates a backup history file in
    the WAL archive area.  The history file includes the label given to
    pg_start_backup, the starting and ending WAL offsets for
    the backup, and the starting and ending times of the backup.  The return
    value is the backup's ending WAL offset (which again may be of little
    interest).
   
For details about proper usage of these functions, see Section 22.3.