Creating and Managing Scheduled Tasks

GaussDB(DWS) allows users to create scheduled tasks, which are automatically executed at specified time points, reducing O&M workload.

Database complies with the Oracle scheduled task function using the DBMS.JOB interface, which can be used to create scheduled tasks, execute tasks automatically, delete a task, and modify task attributes(including task ID, enable/disable a task, the task triggering time/interval and task contents).

  • The hybrid data warehouse (standalone) does not support scheduled tasks.
  • The execution statements of scheduled tasks are not recorded in the Real-time Top SQL logs. The statements can be recorded only in versions later than 8.2.1.
  • By default, GaussDB(DWS) uses the UTC time. The execution time of the scheduled task needs to be converted to the time zone of the user.

Periodic Task Management

  1. Creates a test table.

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    CREATE TABLE test(id int, time date);

    If the following information is displayed, the table has been created.

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    CREATE TABLE

  2. Create the customized storage procedure.

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    CREATE OR REPLACE PROCEDURE PRC_JOB_1()
AS
N_NUM integer :=1;
BEGIN
FOR I IN 1..1000 LOOP
INSERT INTO test VALUES(I,SYSDATE);
END LOOP;
END;
/

    If the following information is displayed, the procedure has been created.

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    CREATE PROCEDURE

  3. Create a task.

    • Create a task with unspecified job_id and execute the PRC_JOB_1 storage procedure every two minutes.
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      call dbms_job.submit('call public.prc_job_1(); ', sysdate, 'interval ''1 minute''', :a);
job
-----
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(1 row)
    • Create task with specified job_id.
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      call dbms_job.isubmit(2,'call public.prc_job_1(); ', sysdate, 'interval ''1 minute''');
isubmit
---------

(1 row)

  4. View the created task information about the current user in the USER_JOBS view.

    Only the system administrator can access this system view. For details about the fields, see Table 1.

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    select job,dbname,start_date,last_date,this_date,next_date,broken,status,interval,failures,what from user_jobs;
 job |  dbname  |         start_date         |         last_date          |         this_date          |      next_date      | broken | status |      interval       | failures |           what

-----+----------+----------------------------+----------------------------+----------------------------+---------------------+--------+--------+---------------------+----------+----------------
-----------
   1 | db_demo | 2022-03-25 07:58:01.829436 | 2022-03-25 07:58:03.174817 | 2022-03-25 07:58:01.829436 | 2022-03-25 07:59:01 | n      | s      | interval '1 minute' |        0 | call public.prc
_job_1();
   2 | db_demo | 2022-03-25 07:58:15.893383 | 2022-03-25 07:58:16.608959 | 2022-03-25 07:58:15.893383 | 2022-03-25 07:59:15 | n      | s      | interval '1 minute' |        0 | call public.prc
_job_1();
(2 rows)

  5. Stop a task.

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    call dbms_job.broken(1,true);
broken
--------

(1 row)

  6. Start a task.

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    call dbms_job.broken(1,false);
broken
--------

(1 row)

  7. Modify attributes of a task.

    • Modify the Next_date parameter information about a task. For example, change the value of Next_date of Job1 to 1 hour.
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      call dbms_job.next_date(1, sysdate+1.0/24);
next_date
-----------

(1 row)
    • Modify the Interval parameter information of a task. For example, change the value of Interval of Job1 to 1 hour.
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      call dbms_job.interval(1,'sysdate + 1.0/24');
interval
----------

(1 row)
    • Modify the What parameter information of a JOB. For example, change What of Job1 to insert into public.test values(333, sysdate+5).
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      call dbms_job.what(1,'insert into public.test values(333, sysdate+5);');
what
------

(1 row)
    • Modify Next_date, Interval, and What parameter information of JOB.
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      call dbms_job.change(1, 'call public.prc_job_1();', sysdate, 'interval ''1 minute''');
change
--------

(1 row)

  8. Delete a job.

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    call dbms_job.remove(1);
remove
--------

(1 row)

  9. Set job permissions.

    • During the creation of a job, the job is bound to the user and database that created the job. Accordingly, the user and database are added to dbname and log_user columns in the pg_job system view, respectively.
    • If the current user is a DBA user, system administrator, or the user who created the job (log_user in pg_job), the user has the permissions to delete or modify parameter settings of the job using the remove, change, next_data, what, or interval interface. Otherwise, the system displays a message indicating that the current user has no permission to perform operations on the JOB.
    • If the current database is the one that created a job, (that is, dbname in pg_job), you can delete or modify parameter settings of the job using the remove, change, next_data, what, or interval interface.
    • When deleting the database that created a job, (that is, dbname in pg_job), the system associatively deletes the job records of the database.
    • When deleting the user who created a job, (that is, log_user in pg_job), the system associatively deletes the job records of the user.

Parent topic: Defining Database Objects