Optimising Sargable Conjunctive Predicate Queries in the Context of Big Data

With the continued increase in the volume of data, the volume dimension of big data has become a significant factor in estimating query time. When all other factors are held constant, query time increases as the volume of data increases and vice versa. To enhance query time, several techniques have come out of research efforts in this direction. One of such techniques is factorisation of query predicates. Factorisation has been used as a query optimization technique for the general class of predicates but has been found inapplicable to the subclass of sargable conjunctive equality predicates. Experiments performed exposed a peculiar nature of sargable conjunctive equality predicates based on which insight, the concatenated predicate model was formulated as capable of optimising sargable conjunctive equality predicates. Equations from research results were combined in a way that theorems describing the application and optimality of the concatenated predicate model were derived and proved

Abstract A Strategy for Decomposing Complex Queries in a Heterogeneous DDB

In a generalised distributed database system with decentralised controls and heterogeneous and pre-existing nodes, queries can be very complex, particularly if they provide a data integration facility. We describe here an algorithm for the optimal decomposition of such queries into subqueries, taking into consideration the availability of nodal operations (some nodes may not be able to perform all operations) and other factors. This algorithm is being implemented in the PRECI* system. In a distributed database system, an efficient query processing strategy is essential for ameliorated performance. In general there will be many possible strategies for processing a particular query, and ideally each of these should be evaluated in order to determine the best strategy. Unfortunately, however, the,problem of selecting optimal strategies for complex queries 1s NP-complete, so it is not feasible to evaluate every strategy for such queries. Many query decomposition algorithms have therefore been designed to produce optimal or near-optimal strategies only under a set of highly restrictive assumptions that apply to a particular implementation (1, 2). The only algorithm developed for a DDB which allows heterogeneous pre-existing databases as nodes is that of the MULTIBASE project (3). The