用于在Oracle 12c上用ROWNUM锁定的更新跳过

Question

I searched all the forum but I didn't find any clue about it. I have a staging table that multiple threads consume. To avoid deadlock, I'm using something like this:

SELECT ID_MESSAGE
FROM TB_STAGE_IN S 
WHERE S.CD_STATUS = 0 
AND S.ID_JOB_SCHEDULE IS NULL 
AND ROWNUM <= 10000 
FOR UPDATE SKIP LOCKED; 

It works fine, but the threads don't reach the max of 10,000 rows. It's like:

• Thread 1: 5000
• Thread 2: 3000
• Thread 2: 2000

I know that happens because the rownumber for them is the same, but the table has thousands and thousands of rows. What I really need is the thread gets 10,000 rows unlocked on every step.

I tried using FETCH FIRST 10000 ROWS ONLY, but I receive the message below: ORA-02014: cannot select FOR UPDATE from view with DISTINCT, GROUP BY, etc.

Could you all please help me?

Thanks for the kind.

Answer 1

Ask Tom has a suggestion that goes like this

open C;  -- cursor C is select ... for update skip locked;

loop
  fetch C bulk collect into :my_array limit 100;
  append :my_array to :to_be_processed_array;
  exit when c%notfound or :to_be_processed_array.count >= 10000;
end loop;

-- process any rows in :to_be_processed_array

close C;