Manual transaction management in DBD::Pg
My understanding is that if I want to manually manage transactions, I should turn off AutoCommit.
No, quite the opposite. Setting AutoCommit to 0 starts a transaction, so you want to set it to 1. To have your changes committed automatically (AutoCommit => 1) is to have the database not use transactions, which is the opposite of what you want.
My understanding is that if I want to manually manage transactions, I should turn off AutoCommit.
Correct.
However, DBD::Pg automatically starts your transactions for you. You can't start the transactions manually. Your best option is to leave autocommit off and then just do:
$dbh->commit;when you are ready to commit. This will both commit the existing transaction and start a new transaction.
Now if you set autocommit to on, then anything that exists outside of a transaction becomes its own transaction, one transaction per statement. If you want to be assured of manually managing transactions, you want to set it off.