Description

• The caching of accessed disk pages has been successfully used for decades in database technology, resulting in effective amortization of I/O operations needed within a stream of query or update requests. • The modern complex databases, like multimedia databases, the I/O cost becomes a minor performance factor. • In metric access methods (MAMs), used for similarity search in complex unstructured data, have been designed to minimize rather the number of distance computations than I/O cost (when indexing or querying). • I/O caching in traditional databases, in this paper we introduce the idea of distance caching for usage with MAMs—a novel approach to streamline similarity data. • The D-cache, a main-memory data structure which can be easily implemented into any MAM, in order to spare the distance computations spent by queries/updates. • The two state-of-the-art MAMs to make use of D-cache—the M-tree and Pivot tables. • The D-file, an index-free MAM based on simple sequential search augmented by D-cache. • The experimental evaluation shows that performance gain achieved due to D-cache is significant for all the MAMs, especially for the D-file.