Distributive Join Strategy Based on Tuple Inversion

In this paper, we propose a new direction for distributive join operations. We assume that there will be a scalable distributed computer system in which many computers (processors) are connected through a communication network that can be in a LAN or as part of the Internet with sufficient bandwidth. A relational database is then distributed across this network of processors. However, in our approach, the distribution of the database is very fine-grained and is based on the Distributed Hash Table (DHT) concept. A tuple of a table is assigned to a specific processor by using a fair hash function applied to its key value. For each joinable attribute, an inverted file list is further generated and distributed again based on the DHT. This pre-distribution is done when the tuple enters the system and therefore does not require any distribution of data tuples on the fly when the join is executed. When a join operation request is broadcast, each processor performs a local join and the results are sent back to a query processor which, in turn, merges the join results and returns them to the user. Note that the distribution of the DHT of the inverted file lists can be either pre-processed or distributed on the fly. If the lists are pre-processed and distributed, they have to be maintained. We evaluate our approach by comparing it empirically to two other approaches: the naive join method and the fully distributed join method. The results show a significantly higher performance of our method for a wide range of possible parameter

A survey of parallel execution strategies for transitive closure and logic programs

An important feature of database technology of the nineties is the use of parallelism for speeding up the execution of complex queries. This technology is being tested in several experimental database architectures and a few commercial systems for conventional select-project-join queries. In particular, hash-based fragmentation is used to distribute data to disks under the control of different processors in order to perform selections and joins in parallel. With the development of new query languages, and in particular with the definition of transitive closure queries and of more general logic programming queries, the new dimension of recursion has been added to query processing. Recursive queries are complex; at the same time, their regular structure is particularly suited for parallel execution, and parallelism may give a high efficiency gain. We survey the approaches to parallel execution of recursive queries that have been presented in the recent literature. We observe that research on parallel execution of recursive queries is separated into two distinct subareas, one focused on the transitive closure of Relational Algebra expressions, the other one focused on optimization of more general Datalog queries. Though the subareas seem radically different because of the approach and formalism used, they have many common features. This is not surprising, because most typical Datalog queries can be solved by means of the transitive closure of simple algebraic expressions. We first analyze the relationship between the transitive closure of expressions in Relational Algebra and Datalog programs. We then review sequential methods for evaluating transitive closure, distinguishing iterative and direct methods. We address the parallelization of these methods, by discussing various forms of parallelization. Data fragmentation plays an important role in obtaining parallel execution; we describe hash-based and semantic fragmentation. Finally, we consider Datalog queries, and present general methods for parallel rule execution; we recognize the similarities between these methods and the methods reviewed previously, when the former are applied to linear Datalog queries. We also provide a quantitative analysis that shows the impact of the initial data distribution on the performance of methods

Parallelizing Windowed Stream Joins in a Shared-Nothing Cluster

The availability of large number of processing nodes in a parallel and distributed computing environment enables sophisticated real time processing over high speed data streams, as required by many emerging applications. Sliding window stream joins are among the most important operators in a stream processing system. In this paper, we consider the issue of parallelizing a sliding window stream join operator over a shared nothing cluster. We propose a framework, based on fixed or predefined communication pattern, to distribute the join processing loads over the shared-nothing cluster. We consider various overheads while scaling over a large number of nodes, and propose solution methodologies to cope with the issues. We implement the algorithm over a cluster using a message passing system, and present the experimental results showing the effectiveness of the join processing algorithm.Comment: 11 page

Automatic Parallelization of Database Queries

Although automatic parallelization of conventional language programs is now widely accepted, relatively little emphasis has been placed on automatic parallelization of database query programs (sometimes referred to as “multiple queries” ). In this paper, we discuss the unique problems associated with automatic parallelization of database programs. From this discussion, we derive a complete approach to automatic parallelization of database programs. Beside integrating a number of existing techniques, our approach relies heavily on several new concepts, including the concepts of “algorithm-level” analysis and hybrid static/dynamic scheduling

Dynamic Range Partitioning in Multiprocessor Database Implementations

Multiprocessor implementation of the relational database operators has recently received great attention in literature [1-4, 8, 11]. As the complexity of implementing the relational operators rests on the inter-node communication patterns involved in an operation, greater research attention has been focused on Join algorithms. The Join traffic patterns subsume those of the remaining relational operators. To effectively exploit parallelism in bucket based join implementations, the domain of the joining attributes must be partitioned into equal subranges. That is, the processing of each subrange requires roughly the same amount of time. A skewed distribution of workload significantly hinders performance. As relations exhibit a non-uniform attribute value distribution, possibly resulting from a previous operation, a priori determination of subrange boundary conditions results in a non-balanced workload across the processors. Performance degradation in parallel systems employing such static boundary subrange partitioning is demonstrated in Lakshmi and Yu [6]. That study exemplified that even a low degree of attribute skew results in a significant performance penalty. This paper proposes a statistical algorithm for dynamic determination of domain partitioning in bucket based join implementations. This statistics-based approach guarantees a near-uniform processor workload. A parameterization of the sample size versus the number of tuples is developed, and a proof of the validity of the approach is discussed. A simple illustrative example is presented

Perbandingan Pencarian Data Menggunakan Query Hash Join dan Query Nested Join

Pengaksesan data atau pencarian data dengan menggunakan Query atau Join pada aplikasi yang terhubung dengan sebuah database perlu memperhatikan ketepatgunaan implementasi dari data itu sendiri serta waktu prosesnya. Ada banyak cara yang dapat dilakukan oleh database manajemen sistem dalam memproses dan menghasilkan jawaban sebuah query. Semua cara pada akhirnya akan menghasilkan jawaban (output) yang sama tetapi pasti mempunyai harga yang berbeda-beda, seperti kecepatan waktu untuk merespon data. Beberapa query yang sering digunakan untuk pemrosesan data yaitu Query Hash Join dan Query Nested Join, kedua query memiliki algoritma yang berbeda tapi menghasilkan output yang sama. Dengan menggunakan aplikasi yang dirancang menggunakan Microsoft Visual Studi 2010 dan Microsoft SQL Server 2008 berbasis jaringan untuk melakukan pengujian kedua algoritma atau query dengan parameter running time atau kecepatan waktu merespon data. Pengujian dilakukan dengan jumlah tabel yang dihubungkan dan jumlah baris/record. Hasil dari penelitian adalah kecepatan waktu query dalam merespon data untuk jumlah data yang kecil query hash join lebih baik dibandingkan dengan jumlah data yang besar query nested join

Efficient permutation-based range-join algorithms on N-dimensionalmeshes using data-shifting

©2001 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.In this paper, we present two efficient parallel algorithms for computing a non-equijoin, range-join, of two relations an N-dimensional mesh-connected computers. The proposed algorithms uses the data-shifting approach to effectively permute every sorted subset of relation S to each processor in turn recursively in dimensions from low to high, where it is joined with the local subset of relation RShao Dong Chen, Hong Shen, Rodeny Topo