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 a current query of the backend.
Return type: boolean
Note: pg_cancel_backend sends a query cancellation signal (SIGINT) 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.
Example:
SELECT pid FROM pg_stat_activity WHERE stmt_type ='RESET';
pid
-----------------
281471222065200
(1 row)
SELECT pg_cancel_backend(281471222065200);
pg_cancel_backend
-------------------
t
(1 row)
pg_reload_conf()¶
Description: Notifies the server process to reload the configuration file.
Return type: boolean
Note: pg_reload_conf sends a SIGHUP signal to the server. As a result, all server processes reload their configuration files.
Example:
SELECT pg_reload_conf();
pg_reload_conf
----------------
t
(1 row)
pg_rotate_logfile()¶
Description: Rotates the log files of the server.
Return type: boolean
Note: pg_rotate_logfile instructs the log file manager to immediately switch to a new output file. This function is valid only if the built-in log collector is running.
Example:
SELECT pg_rotate_logfile();
pg_rotate_logfile
-------------------
t
(1 row)
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.
Example:
SELECT pid FROM pg_stat_activity;
pid
-----------------
140657876268816
140433774061312
140433587902208
140433656592128
140433723717376
140433637189376
140433552770816
140433481983744
140433349310208
(9 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.
Example:
SELECT pid FROM pg_stat_activity WHERE stmt_type ='RESET';
pid
-----------------
281471222065200
(1 row)
SELECT pg_wlm_jump_queue(281471222065200);
pg_wlm_jump_queue
-------------------
t
(1 row)
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.
pg_cancel_query(queryId int)¶
Description: Cancels a current query of the backend. This function is supported in 8.1.2 or later.
Return type: boolean
Note: pg_cancel_query sends a query cancellation signal (SIGINT) to the backend process identified by query_id. The query_id of an active backend process can be found in the query_id column of the pg_stat_activity view.
Example:
SELECT query_id FROM pgxc_stat_activity WHERE stmt_type ='RESET';
query_id
----------
0
0
(2 rows)
SELECT pg_cancel_query(0);
pg_cancel_query
-----------------
f
(1 row)
pgxc_cancel_query(queryId int)¶
Description: Cancels the query that is being executed in the current cluster. This function is supported in 8.1.2 or later.
Return type: boolean
Note: If the queries of all nodes have been canceled, true is returned. Otherwise, false is returned.
Example:
SELECT query_id FROM pgxc_stat_activity WHERE stmt_type ='RESET';
query_id
----------
0
0
(2 rows)
SELECT pgxc_cancel_query(0);
pgxc_cancel_query
-------------------
f
(1 row)
pg_terminate_query(queryId int)¶
Description: Terminates a current query of the backend. This function is supported in 8.1.2 or later.
Return type: boolean
Example:
SELECT query_id FROM pgxc_stat_activity WHERE stmt_type ='RESET';
query_id
----------
0
0
(2 rows)
SELECT pg_terminate_query(0);
pg_terminate_query
--------------------
f
(1 row)
pgxc_terminate_query(queryId int)¶
Description: Terminates the query that is being executed in the current cluster. This function is supported in 8.1.2 or later.
Return type: boolean
Example:
SELECT query_id FROM pgxc_stat_activity;
query_id
-----------------
72339069014638631
(1 rows)
SELECT pgxc_terminate_query(72339069014638631);
pgxc_terminate_query
----------------------
t
(1 row)