Using the lock manager to choose timestamps

Our goal is to support transaction-time functionality that enables the coexistence of ordinary, non-temporal tables with transaction-time tables. In such a system, each transaction updating a transaction-time or snapshot table must include a timestamp for its updated data that correctly reflects the serialization order of the transactions, including transactions on ordinary tables. A serious issue is coping with SQL CURRENT/spl I.bar/TIME functions, which should return a time consistent with a transaction's timestamp and serialization order. Prior timestamping techniques cannot support such junctions with this desired semantics. We show how to compatibly extend conventional database functionality for transaction-time support by exploiting the database system lock manager and by utilizing a spectrum of optimizations.