Conjunctive query algorithm

In computer science, an enumeration algorithm is an algorithm that enumerates the answers to a computational problem.
Formally, such an algorithm applies to problems that take an input and produce a list of solutions, similarly to function problems.
For each input, the enumeration algorithm must produce the list of all solutions, without duplicates, and then halt.
The performance of an enumeration algorithm is measured in terms of the time required to produce the solutions, either in terms of the total time required to produce all solutions, or in terms of the maximal delay between two consecutive solutions and in terms of a preprocessing time, counted as the time before outputting the first solution.
This complexity can be expressed in terms of the size of the input, the size of each individual output, or the total size of the set of all outputs, similarly to what is done with output-sensitive algorithms.