DataMapper ORM v1.8.1

[eluser]WanWizard[/eluser]
If you haven't enabled 'auto_transaction' in the config or in the model, Datamapper doesn't use any transactions.

If you have, MySQL doesn't support nested transactions, so if you start a second one (which $u->save() does), the first one is committed automatically.

The only way around it is to set 'auto_transation' to FALSE, en code your own begin and end of the transaction.

Cascading delete is automatic and enabled by default. It only deletes related records if they are detected to be children. If the records contains a FK, it will consider the record to be the child. To avoid deleting the parent (and by cascading delete half your table), it will set the FK to null to delete only the relation.