1. A method of processing a flashback query to return data from a prior target logical state of a database system, the method comprising the steps of: receiving, at said database system, said flashback query, wherein a response to the flashback query requires said database system to retrieve said data from said prior target logical state of said database system, where the prior target logical state corresponds to a target time; and in response to receiving said flashback query, computing said flashback query using an index structure that is not natively supported by said database system to retrieve said data, wherein said data that is retrieved using said index structure accurately reflects said prior target logical state of said database system, but does not reflect a different logical state of said database system that exists after said target logical state; wherein the method is performed by one or more computing devices.