There might/probably is a better way to achieve what I am trying to achieve. Let me explain:
I've got a typical Customer/Order/Orderdetail relation. merge() appeals to me because it does most all the same work I'd otherwise need to do. I get passed to me an "Order" object will the customer object and the details objects. Now, when I run merge, if there are any changes to the customer, these get automagically updated. If a line is missing, it is automatically deleted. If a new line exists, it is automatically inserted. session.merge() does all this. However, the above is a bit too simplified. If the Customer's primary key is not supplied, I need to create this in a special way (not from a sequence) and then insert it. In this case, I don't even want merge to *attempt* to get() from the database first because if, by chance, the customerid I construct is already in use, I do not want to accidentally update that record, I *want* the database to complain on the INSERT that the primary key already exists. Same with the order and orderdetails. If an orderdetail is supplied to me without a primary key, I would like to choose the next appropriate primary key and INSERT for that particular record, so that (if something is messed up or a race condition exists with another instance of the program choosing the same primary key) I get a database error instead of merge() accidentally updating that other record. I don't want to give up the benefits of merge() by programmatically figuring this out myself. In other words, if I add() to the session all the lines I *know* should be INSERTs then I need to work out all the other magical things merge() is doing for me (like deleting missing lines). I tried seeing what would happen if I just called session.add() for the cases of an INSERT and then calling session.merge() for the entire cascading order(customer/details), but when I tried that I got: New Instance conflicts with persistent instance type error. I assume this means: you tried to session.add() and object and now I just looked up this same instance during the session.merge(). So instead, I was wondering if there is a way to mark an object in such a way that when session.merge() recursively hits this object, it knows to not bother with the fetch but instead does a session.add()? Otherwise, is there a better approach to what I am trying to accomplish? -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
