Chapter 4. Transactions


Disabling and enabling automatic commits
begin_work(), commit_work() and rollback_work()

There are three mutually exclusive ways to implement transactions. They cannot be combined together. Pick one, and use it exclusively.

Disabling and enabling automatic commits

void move_money(const x::sql::connection &conn,
                int from_account, int to_account, double amount)
    auto statement=conn->prepare("INSERT INTO ledger(account_id, amount) VALUES(?, ?)");
    conn->execute(from_account, -amount);
    conn->execute(to_account, amount);

autocommit() changes the connection's autocommit mode. The default true setting commits each statement to the database, automatically. After turning it off, an explicit commit() commits all executed statements; and rollback() rolls them back. Afterwards, the next statement creates another transaction, collecting statements to be commit()ed or rollback()ed. Changing the autocommit setting back to true reenables automatic commit of every transaction.

commit() and rollback() take an optional bool parameter, which defaults to a false value. Explicitly setting the parameter to true has the effect of commiting or rolling back the transaction and reenabling autocommit mode, in one operation.