Transactions and purging
This package provides executors for doctrine/orm, doctrine/mongodb-odm
and doctrine/phpcr-odm.
The executors purge the database, then load the fixtures. The ORM
implementation wraps these two steps in a database transaction, which
provides a nice additional property: atomicity.
Because of that transaction, the loading either succeeds or fails
cleanly, meaning nothing is actually changed in the database if the
loading fails. It delegates the purging to a separate class that can be
configured to either use a TRUNCATE or a DELETE statement to
empty tables.
Not all RDBMS have the capability to allow TRUNCATE statements
inside transactions though. Notably, MySQL will produce the infamous
"There is no active transaction" message when we attempt to close a
transaction that was already implicitly closed.