BIT 22 (1982), 150-168 P A R T I A L - M A T C H R E T R I E V A L F O R D Y N A M I C F I L E S JOHN W. LLOYD and K. RAMAMOHANARAO Department of Computer Science, University of Melbourne, Melbourne, Australia Abstract. This paper studies file designs for answering partial-match queries for dynamic files. A partial-match query is a specification of the value of zero or more fields in a record. An answer to a query consists of a listing of all records in the file satisfying the values specified. The main contribution is a general method whereby certain primary key hasing schemes can be ex- tended to partial-match retrieval schemes. These partial-match retrieval designs can handle arbitrarily dynamic files and can be optimized with respect to the number of page faults required to answer a query. We illustrate the method by considering in detail the extension of two recent dynamic primary key hashing schemes. Keywords and phrases : partial-match retrieval, dynamic files, extendible hashing, linear hashing. CR categories: 3.74, 4.33, 4.34. 1. Introduction. In recent years, there has been considerable interest in thespecial case of secondary key retrieval known as partial-match retrieval. See, for example, [1], E2], [3], [7], [8], [9], [10]. To explain what a partial-match query is we need to introduce some termino- logy. A file consists of a series of records. Each record consists of a number of fields which may be specified in a query (that is, these fields are secondary keys), plus other fields which are irrelevant to the considerations here. Let us suppose that there are k fields, ./'1, f2..., ,~, which may be specified in a query. Then a partial-match query is a specification of the values of zero or more of the fields fl,. • -,.)~. An answer to a query is a listing of all records in the file which have the specified values for the specified fields. The main problem addressed by this paper is the problem of handling partial- match queries for a dynamic file. A dynamic file is one for which there are many deletions and insertions. Most designs for partial-match retrieval have been based on hashing functions, which, until recently, has implied application to reasonably static files. However, the primary key hashing schemes of Fagin et al. [4], Litwin [6] and Larson [5] allow the design of efficient partial-match retrieval schemes Received September 10, 1981.