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Server Signaling 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_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:

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    SELECT pid from pg_stat_activity;
       pid       
-----------------
 140657876268816
(1 rows)

SELECT pg_terminate_backend(140657876268816);
 pg_terminate_backend 
----------------------
 t
(1 row)
  • pg_wlm_jump_queue(pid int)

    Description: Moves a task to the top of the CN queue.

    Return type: Boolean

    Note: Each of these functions returns true if they are successful and false otherwise.

  • gs_wlm_switch_cgroup(pid int, cgroup text)

    Description: Moves a job to other Cgroup to improve the job priority.

    Return type: Boolean

    Note: Each of these functions returns true if they are successful and false otherwise.