Abstract NoSQL databases are famed for the characteristics of high scalability, high availability, and high faulttolerance. So NoSQL databases are used in a lot of applications. The data partitioning strategy and frag...Abstract NoSQL databases are famed for the characteristics of high scalability, high availability, and high faulttolerance. So NoSQL databases are used in a lot of applications. The data partitioning strategy and fragment allocation strategy directly affect NoSQL database systems＇ performance. The data partition strategy of large, global databases is performed by horizontally, vertically partitioning or combination of both. In the general way the system scatters the related fragments as possible to improve operations＇ parallel degree. But the operations are usually not very complicated in some applications, and an operation may access to more than one fragment. At the same time, those fragments which have to be accessed by an operation may interact with each other. The general allocation strategies will increase system＇s communication cost during operations execution over sites. In order to improve those applications＇ performance and enable NoSQL database systems to work efficiently, these applications＇ fragments have to be allocated in a reasonable way that can reduce the communication cost i.e., to minimize the total volume of data transmitted during operations execution over sites. A strategy of clustering fragments based onhypergraph is proposed, which can cluster fragments which were accessed together in most operations to the same cluster. The method uses a weighted hypergraph to represent the fragments＇ access pattem of operations. A hypergraph partitioning algorithm is used to cluster fragments in our strategy. This method can reduce the amount of sites that an operation has to span. So it can reduce the communication cost over sites. Experimental results confirm that the proposed technique will effectively contribute in solving fragments re-allocation problem in a specific application environment of NoSQL database system.展开更多
Judicious bisection of hypergraphs asks for a balanced bipartition of the vertex set that optimizes several quantities simultaneously. In this paper, we prove that if G is a hypergraph with n vertices and ni edges of ...Judicious bisection of hypergraphs asks for a balanced bipartition of the vertex set that optimizes several quantities simultaneously. In this paper, we prove that if G is a hypergraph with n vertices and ni edges of size i for i = 1, 2,…, k, then G admits a bisection in which each vertex class spans at mostm1/2＋1/4m2＋…＋（1/2^k）mk＋o（m1＋…＋mk）edges, where G is dense enough or △（G） =o（n） but has no isolated vertex, which turns out to be a bisection version of a conjecture proposed by Bollobas and Scott.展开更多
基金Thanks to the anonymous reviewers for their insightful comments. This work was supported by National High Technology Research and Development Plan of China （＂863＂ plan）（2012AA012600, 2012AA01A402, 2012AA01A401, 2011AA010702 and 2010AA012505） the National Natural Science Foundation of China （Grant Nos. 60933005 and 91124002）+1 种基金 the National Key Technology Research and Development Program of China （2012BAH38B04 and 2012BAH38B06） National 242 Information Security Program of China （2011A010）.
文摘Abstract NoSQL databases are famed for the characteristics of high scalability, high availability, and high faulttolerance. So NoSQL databases are used in a lot of applications. The data partitioning strategy and fragment allocation strategy directly affect NoSQL database systems＇ performance. The data partition strategy of large, global databases is performed by horizontally, vertically partitioning or combination of both. In the general way the system scatters the related fragments as possible to improve operations＇ parallel degree. But the operations are usually not very complicated in some applications, and an operation may access to more than one fragment. At the same time, those fragments which have to be accessed by an operation may interact with each other. The general allocation strategies will increase system＇s communication cost during operations execution over sites. In order to improve those applications＇ performance and enable NoSQL database systems to work efficiently, these applications＇ fragments have to be allocated in a reasonable way that can reduce the communication cost i.e., to minimize the total volume of data transmitted during operations execution over sites. A strategy of clustering fragments based onhypergraph is proposed, which can cluster fragments which were accessed together in most operations to the same cluster. The method uses a weighted hypergraph to represent the fragments＇ access pattem of operations. A hypergraph partitioning algorithm is used to cluster fragments in our strategy. This method can reduce the amount of sites that an operation has to span. So it can reduce the communication cost over sites. Experimental results confirm that the proposed technique will effectively contribute in solving fragments re-allocation problem in a specific application environment of NoSQL database system.
文摘Judicious bisection of hypergraphs asks for a balanced bipartition of the vertex set that optimizes several quantities simultaneously. In this paper, we prove that if G is a hypergraph with n vertices and ni edges of size i for i = 1, 2,…, k, then G admits a bisection in which each vertex class spans at mostm1/2＋1/4m2＋…＋（1/2^k）mk＋o（m1＋…＋mk）edges, where G is dense enough or △（G） =o（n） but has no isolated vertex, which turns out to be a bisection version of a conjecture proposed by Bollobas and Scott.
