Performance Analysis of Three Text-Join Algorithms

When a multidatabase system contains textual database systems (i.e., information retrieval systems), queries against the global schema of the multidatabase system may contain a new type of joins-joins between attributes ol textual type. Three algorithms for processing such a type of joins are presented and their l/O costs are analyzed in this paper. Since such a type of joins often involves document collections of very large size, it is very important to find etficrent algorithms to process them. The three algorithms differ on whether the documents themselves or the inverted files on the documents are used to process the join. Our analysis and the simulation results indicate that the relative performance of these algorithms depends on the input document collections, system characteristics, and the input query. For each algorithm, the type of input document collections with which the algorithm is likely to perform well is identified. An integrated algorithm that automatically selects the best algorithm to use is also proposed. lndexTerms-Query processing, textual database, iniormation retrieval, join algorithm, multidatabase.