1. An apparatus comprising: at least one processor; and a computer readable storage medium having computer readable program code embodied therewith and executable by the at least one processor, the computer readable program code comprising: computer readable program code configured to send at least one query to a data warehouse; computer readable program code configured to evaluate a trigger condition; computer readable program code configured to, responsive to a determination that the trigger condition is not satisfied by a query result obtained from the at least one query sent to the data warehouse and the trigger condition is close to being true, send at least one differential query to at least one remote data source; and computer readable program code configured to determine an aggregate query result, the aggregate query result comprising an aggregation of the query result obtained from the at least one query sent to the data warehouse and at least one query result obtained from the at least one differential query.