bulk collect using “for update”

Question

I run into an interesting and unexpected issue when processing records in Oracle (11g) using BULK COLLECT.

The following code was running great, processing through

Answer 1

Adding to Justin's Explantion.

You should have seen the below error message.Not sure, if your Exception handler suppressed this.

And the message itself explains a Lot!

For this kind of Updates, it is better to create a shadow copy of the main table, and let the public synonym point to it. While some batch id, creates a private synonym to our main table and perform the batch operations, to keep it simpler for maintenance.

Error report -
ORA-01002: fetch out of sequence
ORA-06512: at line 7
01002. 00000 -  "fetch out of sequence"
*Cause:    This error means that a fetch has been attempted from a cursor
           which is no longer valid.  Note that a PL/SQL cursor loop
           implicitly does fetches, and thus may also cause this error.
           There are a number of possible causes for this error, including:
           1) Fetching from a cursor after the last row has been retrieved
           and the ORA-1403 error returned.
           2) If the cursor has been opened with the FOR UPDATE clause,
           fetching after a COMMIT has been issued will return the error.
           3) Rebinding any placeholders in the SQL statement, then issuing
           a fetch before reexecuting the statement.
*Action:   1) Do not issue a fetch statement after the last row has been
           retrieved - there are no more rows to fetch.
           2) Do not issue a COMMIT inside a fetch loop for a cursor
           that has been opened FOR UPDATE.
           3) Reexecute the statement after rebinding, then attempt to
           fetch again.

Also, you can change you Logic by Using rowid

An Example for Docs:

DECLARE
-- if "FOR UPDATE OF salary" is included on following line, an error is raised
   CURSOR c1 IS SELECT e.*,rowid FROM employees e;
   emp_rec  employees%ROWTYPE;
BEGIN
   OPEN c1;
   LOOP
     FETCH c1 INTO emp_rec; -- FETCH fails on the second iteration with FOR UPDATE
     EXIT WHEN c1%NOTFOUND;
     IF emp_rec.employee_id = 105 THEN
       UPDATE employees SET salary = salary * 1.05 WHERE rowid = emp_rec.rowid;
         -- this mimics WHERE CURRENT OF c1
     END IF;
     COMMIT;  -- releases locks
   END LOOP;
END;
/

You have to fetch a record row by row!! update it using the ROWID AND COMMIT immediately . And then proceed to the next row!

But by this, you have to give up the Bulk Binding option.

Answer 2

The problem is that you're trying to do a fetch across a commit.

When you open My_Data_Cur with the for update clause, Oracle has to lock every row in the My_Data_1 table before it can return any rows. When you commit, Oracle has to release all those locks (the locks Oracle creates do not span transactions). Since the cursor no longer has the locks that you requested, Oracle has to close the cursor since it can no longer satisfy the for update clause. The second fetch, therefore, must return 0 rows.

The most logical approach would almost always be to remove the commit and do the entire thing in a single transaction. If you really, really, really need separate transactions, you would need to open and close the cursor for every iteration of the loop. Most likely, you'd want to do something to restrict the cursor to only return 100 rows every time it is opened (i.e. a rownum <= 100 clause) so that you wouldn't incur the expense of visiting every row to place the lock and then every row other than the 100 that you processed and deleted to release the lock every time through the loop.