A Survey of Techniques for Answering Top-k Queries

Top-k queries are useful in retrieving top-k records from a given set of records depending on the value of a function F on their attributes. Many techniques have been proposed in database literature for answering top-k queries. These are mainly categorized into three: Sorted-list based, layer based and View based. In first category, records are sorted along each dimension and then assigned a rank to each of the records using parallel scanning method. Threshold Algorithm (TA) and Fagin’s Algorithm (FA) are the examples of sorted-list based category. Second category is layer based category, in which all the records are organized into layers such as in onion technique and robust indexing technique. Third category includes methods such as PREFER and LPTA (Linear Programming Adaptation of Threshold Algorithm) and processing is based on the materialized views.