If a query will result in a large-scale data retrieval, the user should be informed and required to confirm the transaction or to narrow the query before processing.
Additional Information:
In this regard, it may be helpful to permit a user to set some upper bound for data output, in effect to define what constitutes a "large-scale" retrieval. It may help a user to decide whether to confirm or modify a pending query, if the user can request a partial display of the currently specified data output.