This paper concerns the following problem: given a set of multi-attribute records, a fixed number of buckets and a two-disk system, arrange the records into the buckets and then store the buckets between the disks in such a way that, over all possible orthogonal range queries (ORQs), the disk access concurrency is maximized. We shall adopt the multiple key hashing (MKH) method for arranging records into buckets and use the disk modulo (DM) allocation method for storing buckets onto disks. Since the DM allocation method has been shown to be superior to any other allocation methods for allocating an MKH file onto a two-disk system for answering ORQs, the real issue is knowing how to determine an optimal way for organizing the records into buckets based upon the MKH concept.
A performance formula that can be used to evaluate the average response time, over all possible ORQs, of an MKH file in a two-disk system using the DM allocation method is first presented. Based upon this formula, it is shown that our design problem is related to a notoriously difficult problem, namely the Prime Number Problem. Then a performance lower bound and an efficient algorithm for designing optimal MKH files in certain cases are presented. It is pointed out that in some cases the optimal MKH file for ORQs in a two-disk system using the DM allocation method is identical to the optimal MKH file for ORQs in a single-disk system and the optimal average response time in a two-disk system is slightly greater than one half of that in a single-disk system. 相似文献
The continuous top-t most influential place (CTtMIP)query is defined formally and solved efficiently in this paper.A CTtMIP query continuously monitors the t places with the maximum influence from the ... 相似文献
In wireless sensor networks, query execution over a specific geographical region is an essential function for collecting sensed
data. However, sensor nodes deployed in sensor networks have limited battery power. Hence, the minimum number of connected
sensor nodes that covers the queried region in a sensor network must be determined. This paper proposes an efficient distributed
protocol to find a subset of connected sensor nodes to cover the queried region. Each node determines whether to be a sensing node to sense the queried region according to its priority. The proposed protocol can efficiently construct a subset of connected
sensing nodes and respond the query request to the sink node. In addition, the proposed protocol is extended to solve the k-coverage request. Simulation results show that our protocol is more efficient and has a lower communication overhead than
the existing protocol. 相似文献