Server Signal Functions

Server signaling functions send control signals to other server processes. Only system administrators can use these 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_reload_conf()

  Description: Causes all server processes to reload their configuration files (restricted to the system administrator).

  Return type: Boolean

  Note:pg_reload_conf sends a SIGHUP signal to the server (restricted to the system administrator). 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_backend(pid int)

  Description: Terminates a backend thread.

  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 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.

  Example:

  MogDB=# SELECT pid from pg_stat_activity;
         pid
  -----------------
   140657876268816
  (1 rows)
  
  MogDB=# SELECT pg_terminate_backend(140657876268816);
   pg_terminate_backend
  ----------------------
   t
  (1 row)

• pg_terminate_session(pid int64, sessionid int64)

  Description: Terminates a backend session.

  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 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.