Locking order in cursors (Oracle)

I wonder if the order in which records are locked is guaranteed when I use SELECT ... FOR UPDATE in cursors ?
For example,

DECLARE 
CURSOR test_cursor IS 
SELECT field1, field2 
FROM table1 
ORDER BY pk_field
FOR UPDATE OF field1;

When I open such a cursor, will it always lock records in the order of pk_field ?

From what I read so far order of locking is not guaranteed for regular SELECT ... ORDER BY pk_field FOR UPDATE , but I'm not sure if it's true for cursors. I'd expect it does lock in the order set in ORDER BY clause for cursors; however, I cannot find confirmation.

Thank you.

The order in which individual rows will be locked is undefined and certainly not something you should rely on since it will depend on the query plan.

In general, I would expect that the rows would not be locked in order-- the optimizer would generally expect it to be more efficient to access all the data unordered and then apply the ORDER BY. If there was a composite index on pk_field, field1, field2, I could see the optimizer potentially choosing to do an ordered scan of the index and then locking each row in the table but that seems unlikely.

StackExchange Database Administrators Q#19029, answer score: 2