Server Signal Functions

Server signal functions send control signals to other server processes. Only the system administrator has the permission to execute the following functions:

pg_cancel_backend(pid int)
Description: Cancels the current query of a backend.

Return type: Boolean

Note: pg_cancel_backend sends a query cancellation (SIGINT) signal to the backend process identified by pid. The PID of an active backend process can be found in the pid column of the pg_stat_activity view, or can be found by listing the database process using ps on the server. A user with the SYSADMIN permission, the owner of the database connected to the backend process, the owner of the backend process, or a user who inherits the gs_role_signal_backend permission of the built-in role has the permission to use this function.
pg_cancel_session(pid bigint, sessionid bigint)
Description: Cancels a backend session.

Return type: Boolean

Note: The input parameters of pg_cancel_session can be queried using the pid and sessionid fields in pg_stat_activity. It can be used to clear inactive sessions in thread pool mode.
pg_cancel_invalid_query()
Description: Cancels the invalid query of a backend.

Return type: Boolean

Note: Only the system administrator has the permission to cancel queries that are running in the backend of a degraded GTM.
pg_reload_conf()
Description: Causes all server processes to reload their configuration files.

Return type: Boolean

Note: pg_reload_conf sends a SIGHUP signal to the server. As a result, all server processes reload their configuration files.
pg_rotate_logfile()
Description: Rotates the log files of the server.

Return type: Boolean

Note: pg_rotate_logfile sends a signal to the log file manager, instructing the manager to immediately switch to a new output file. This function works only when redirect_stderr is used for log output. Otherwise, no log file manager subprocess exists.
pg_terminate_session(pid bigint, sessionid bigint)
Description: Terminates a backend session.

Return type: Boolean

Note: The input parameters of this function can be queried using the pid and sessionid fields in pg_stat_activity. It can be used to clear inactive sessions in thread pool mode. A user with the SYSADMIN permission, the owner of the database connected to the session, the owner of the session, or a user who inherits the gs_role_signal_backend permission of the built-in role has the permission to use this function.

pg_terminate_backend(pid int)

Description: Terminates a backend thread. Only the system administrator and thread owner can use this function.

Return type: Boolean

Note: Each of these functions returns true if they are successful and false otherwise. A user with the SYSADMIN permission, the owner of the database connected to the backend thread, the owner of the backend thread, or a user who inherits the gs_role_signal_backend permission of the built-in role can use this function.

Example:

     
          openGauss=# SELECT pid from pg_stat_activity;
       pid       
-----------------
 140657876268816
(1 rows)

openGauss=# SELECT pg_terminate_backend(140657876268816);
 pg_terminate_backend 
----------------------
 t
(1 row)