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pg_cancel_backend(pid int)
pg_reload_conf()
pg_rotate_logfile()
pg_terminate_backend(pid int)
pg_wlm_jump_queue(pid int)
gs_wlm_switch_cgroup(pid int, cgroup text)
pg_cancel_query(queryId int)
pgxc_cancel_query(queryId int)
pg_terminate_query(queryId int)
pgxc_terminate_query(queryId int)

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Help Center/ GaussDB(DWS)/ SQL Syntax Reference (9.1.0.x)/ Functions and Operators/ System Administration Functions/ Server Signaling Functions

Server Signaling Functions

Updated on 2024-09-30 GMT+08:00

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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)