Before revision: We study the question of when we can answer a Conjunctive Query (CQ) with an ordering over the answers by constructing a structure for direct (random) access to the sorted list of answers, without actually materializing this list, so that the construction time is linear (or quasilinear ) in the size of the database.
After revision: We study the question of when we can answer a Conjunctive Query (CQ) with an ordering over the answers , following a preprocessing step that constructs a data structure in time quasilinear in the size of the database.