Enumerating answers to first-order queries over databases of low degree
Abstract
A class of relational databases has low degree if for all delta, all but finitely many databases in the class have degree at most n^delta, where n is the size of the database. Typical examples are databases of bounded degree or of degree bounded by log n. It is known that over a class of databases having low degree, first-order boolean queries can be checked in pseudo-linear time, i.e. in time bounded by n^(1+epsilon), for all epsilon. We generalise this result by considering query evaluation. We show that counting the number of answers to a query can be done in pseudo-linear time and that enumerating the answers to a query can be done with constant delay after a pseudo-linear time preprocessing.