Database transactions support a weak form of multi-version con-currency control by allowing an uncommitted transaction’s writesto be either committed or rolled back by aborting the transaction [8].However, most databases do not allow one user to share the state ofan uncommitted transaction with another user, and most databasesdo not allow the user to find out what data has changed in anuncommitted transaction (the equivalent of git diff). Moreover,in most database systems, an uncommitted transaction may holdlocks and thus prevent other transactions from making progress.