US Patent 7814117 Accessing data from asynchronously maintained index

A method and apparatus for computing queries in a way that is consistent with an index and the underlying base table is provided. A query is computed such that it is consistent with the state of an index and base table as of the last point at which the index and table were synchronized. For example, if an index is maintained asynchronously then it is not necessarily consistent with its base table when a query is to be run against the table and the index. Therefore, the query is computed such that it will be consistent with the last point at which the index and the table were synchronized. In one embodiment, a System Change Number (SCN) of the last successful synchronization operation is used to perform a flashback query on the table.