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Bulk Update

Posted on 2009-07-14
7
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Last Modified: 2013-12-19
Hi

We have a table with following structure.
The table don't have any primary key or unique key.
We want to use Bulk Collect to improve performence.
How can we rewrite the procedure using Bulk collect?

Thanks
Table structure FD_LOG_DATA
==========================
 
ID_BC	                NUMBER
STR_CODE	        NUMBER
ASS_ORDER	        NUMBER
EFFECTIVE_DATE	DATE
EXPIRATION_DATE	DATE
 
PROC
=====
 
create or replace procedure fix_y2k is
  v_max_dt date;
begin
  select max(expiration_date)
    into v_max_dt
    from FD_LOG_DATA;
  for rec in (select expiration_date from FD_LOG_DATA)
    loop
    if add_months(rec.expiration_date,1200) <= v_max_date then
      update FD_LOG_DATA 
         set expiration_date = add_months(rec.expiration_date,1200);
    end if;
  end loop;
end;
/

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Question by:basirana
  • 3
  • 3
7 Comments
 
LVL 143

Assisted Solution

by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 100 total points
ID: 24850268
.hmmm. what about a plain update:
create or replace procedure fix_y2k is
  v_max_dt date;
begin
  select max(expiration_date)
    into v_max_dt
    from FD_LOG_DATA; 
  UPDATE  FD_LOG_DATA 
    SET expiration_date = add_months(rec.expiration_date,1200)
  WHERE rec.expiration_date<= add_months(v_max_date,-1200)
  ;
  commit;
end;
/

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Accepted Solution

by:
sbarwood earned 400 total points
ID: 24851722
basirana, What data volumes are you looking to update? Angellll's solution is fine for small volumes but if the updates are going to hit 10000's rows then you would need a bulk update. Something like this:


CREATE OR REPLACE PROCEDURE fix_y2k IS
  
  TYPE t_rowid IS TABLE OF ROWID INDEX BY PLS_INTEGER;  
  TYPE r_rec IS RECORD ( row_id t_rowid );
  
  rec  r_rec;
  v_max_dt DATE;  
  
BEGIN
    
	SELECT MAX(expiration_date)
    INTO v_max_dt
    FROM FD_LOG_DATA;
	
	LOOP 
	
	  SELECT ROWID
	  BULK COLLECT INTO rec
	  FROM FD_LOG_DATA	  
	  WHERE ADD_MONTHS(expiration_date,1200) <= v_max_dt
	  AND   ROWNUM < 10001;
	  
	  EXIT WHEN rec.row_id.COUNT = 0;
	  
	  FORALL i IN 1..rec.row_id.COUNT
	    UPDATE FD_LOG_DATA 
		SET expiration_date = ADD_MONTHS(expiration_date,1200)
		WHERE ROWID = rec.row_id(i);
	  
	  COMMIT;
	
  END LOOP;
END;
/

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Author Comment

by:basirana
ID: 24852845
The table is having more then 700 million records so it is a very large table.
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Expert Comment

by:sbarwood
ID: 24857326
How many records on average do you think will be updated on a call to that function?
0
 

Author Comment

by:basirana
ID: 24872236
nearly 100000 records.. I am not user how undo tablespace effects.
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Expert Comment

by:sbarwood
ID: 24901809
Have you tried the bulk collect method I suggested and if so did it make any difference to performance? Could be worth trying it with different row counts to see the optimal commit count. i.e. 25000 commit count could be a lot faster than 10000 due to there being 6 less calls to the database but you need to make sure that memory allocation etc is ok. To be honest though, with the volumnes you are talking about (i.e. 100000) memory usage shouldn't be an issue.
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Author Closing Comment

by:basirana
ID: 31603294
Thanks
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