US Patent 7676453 Partial query caching

When a query is performed an execution plan is formed, which is made up of a plurality of plan operators. Before executing any given plan operator, a storage area is checked. If a results set has been stored corresponding to the plan operator, then the cached results set is used instead of the executing the plan operator. If no results set exists that corresponds to the particular plan operator, the plan operator is executed, and the results set that is output may be stored for use by another plan operator of another execution plan.