procedure to delete several records from several tables

[crysu]

P.S.: can't do bulk insert since rows are created in those tables non-stop. If I do bulk insert I'll lose rows that are created when create a new table --> move the desired records --> delete old table --> rename new tables

[PAVB]

1. No
2. Between 70 and 90%

This is a text book case where you may want to consider deleting data by doing inserts instead of doing deletes.

Here is the scenario...
You want to delete 70%+ of the rows sitting on table_a
1- Rename table_a as table_b
2- Create table_a as select * from table_b where v_column_name > sysdate - v_retention_days
3- Build indexes
4- Gather fresh stats.
5- After business approval drop table_b

This is faster, generates less redo and ensures tables and indexes are not fragmented at the end of the process.

Can you afford a maintenance window to do it?

[PAVB]

P.S.: can't do bulk insert since rows are created in those tables non-stop. If I do bulk insert I'll lose rows that are created when create a new table --> move the desired records --> delete old table --> rename new tables

Okay ... when everything fails you have to rely on "delete" to "delete" rows.

Please find below a template I foiund years ago in Metalink, feel free to customize as needed.

------------------------------------------------------  
-- Create procedure
--
-- Remember to replace empno=' || empno
-- by your own purge condition
CREATE OR REPLACE PROCEDURE delete_tab (tablename IN VARCHAR2, 
                                            empno IN NUMBER  , 
                                            nrows IN NUMBER    ) IS
 sSQL1    VARCHAR2(2000);
 sSQL2    VARCHAR2(2000);
 nCount    NUMBER; 
BEGIN
  nCount := 0;
  sSQL1:='delete from '|| tablename || 
         ' where ROWNUM < ' || nrows || ' and empno=' || empno; 
  sSQL2:='select count(ROWID) from ' || tablename || 
         ' where empno= ' || empno;
  LOOP
    EXECUTE IMMEDIATE sSQL1;
    EXECUTE IMMEDIATE sSQL2 INTO nCount;
    DBMS_OUTPUT.PUT_LINE('Existing records: ' || to_char(ncount) );
    commit;    
    EXIT WHEN nCount = 0;
  END LOOP;
END delete_tab;
/
------------------------------------------------------  
-- Execute above created procedure
--
-- In this example we are asking
-- to delete from table BIG_EMP,
-- all rows belonging to empno=7369
-- in batches of 5000 rows
SQL> execute delete_tab('big_emp',7369,5000)
Existing records: 60537
Existing records: 55538
Existing records: 50539
Existing records: 45540
Existing records: 40541
Existing records: 35542
Existing records: 30543
Existing records: 25544
Existing records: 20545
Existing records: 15546
Existing records: 10547
Existing records: 5548
Existing records: 549
Existing records: 0

[crysu]

This is a text book case where you may want to consider deleting data by doing inserts instead of doing deletes.

Here is the scenario...
You want to delete 70%+ of the rows sitting on table_a
1- Rename table_a as table_b
2- Create table_a as select * from table_b where v_column_name > sysdate - v_retention_days
3- Build indexes
4- Gather fresh stats.
5- After business approval drop table_b

This is faster, generates less redo and ensures tables and indexes are not fragmented at the end of the process.

Can you afford a maintenance window to do it?

This will be the perfect case, but it's about a production database that can't be stopped or to interrupt activity to allow me a maintenance window.

I know that recreating the table with only the data that has to remain it is faster and more reliable but I'm afraid of losing rows.

[PAVB]

Check previous post sync issue

[crysu]

Check previous post sync issue

I'll give it a try.

Thanks for sharing this ... and also thanks for your time

Best regards

[PAVB]

Glad to help.

[crysu]

Glad to help.

I tested the script and seems to do the job excellent until now.

Thanks again