class ActiveRecord::TransactionRollbackError

dev.mysql.com/doc/mysql-errors/en/server-error-reference.html#error_er_lock_deadlock<br>* www.postgresql.org/docs/current/static/transaction-iso.html<br><br>See the following:
manually by users.
Due to the aforementioned side-effects, this exception should not be raised
the affected test class (self.use_transactional_tests = false).
these exceptions in tests please consider disabling transactional tests in
cases in their own umbrella transaction. If you absolutely need to handle
In that case, beware of transactional tests, however, because they run test
root transaction block, though.
and internal Active Record state. They can be rescued if you are above the
blocks, because they have side-effects in the actual enclosing transaction
These exceptions should not be generally rescued in nested transaction
back by the database due to a serialization failure or a deadlock.
TransactionRollbackError will be raised when a transaction is rolled