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.

• 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_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.

  For example:

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