Control order of updates in hibernate

Question

I have a table with a unique column, "token", enforced by a unique constraint in the database. In a certain case, I need to change an existing row to have the same token as another existing row, changing the 2nd row to have a new value.

So, say I have:

id;token 0;'aaa' 1;'bbb'

I want id 0 ('aaa') to instead have the token 'bbb'. So I need to change 'bbb' to be 'jfeisefjse', and then I can change 'aaa' to be 'bbb'. This can be done in postgres in a single tranasction.

I've tried to do the same thing in code: In one transaction I get the token from the existing row (row 1), I set it to be a random value, I update the other row (row 0) to have row 1's token, then I commit. However hibernate doesn't respect the order I've done the commits in. It seems to always run the update statement for row 0 first, and postgres complains that it's violating a foreign key constraint.

How can I make hibernate do this? Either force a certain order of update statements, or some other way to do this?

Note: Doing this in two transactions (one for scrambling row 1, then another transaction to update row 0) is not an option.

Answer 1

Session.flush() will force hibernate to write any pending SQL without committing the transaction. It's a bit clunky but sometimes you do need to get a little less 'ORM' and make things just work :)