doc-exports/docs/dws/dev/dws_04_0041.html

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.

   1	CREATE TABLE test(id int, time date);

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

   1	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.

   1	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 ----- 1 (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