Complex transitive closure queries on a fragmented graph

Houstsma, Maurice A. W.; Apers, Peter M. G.; Ceri, Stefano

doi:10.1007/3-540-53507-1_96

Cited by 10 publications

(12 citation statements)

References 15 publications

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“…In the context of PRISMA, parallel algorithms for transitive closure computations are particularly interesting. We are currently investigating this topic [24,25,26], to allow distributed computation of the transitive closure operations that result from our optimization strategy.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, one has started to study the use of distributed computation for transitive closure queries [19,40,44]. This is, however, still a difficult topic, and it seems that one should have some knowledge about the application domain to really benefit from parallel processing, as in [23,24,25]. Although in the context of PRISMA distributed transitive closure algorithms are very interesting, we will not go into this now.…”

Section: Transitive Closurementioning

confidence: 99%

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Algebraic optimization of recursive queries

Houtsma

Apers

1992

Data & Knowledge Engineering

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Over the past few years, much attention has been paid to deductive databases. They offer a logic-based interface, and allow formulation of complex recursive queries. However, they do not offer appropriate update facilities, and do not support existing applications. To overcome these problems an SQL-like interface is required besides a logic-based interface.In the PRISMA project we have developed a tightly-coupled distributed database, on a multiprocessor machine, with two user interfaces: SQL and PRISMAIog. Query optimization is localized in one component: the relational query optimizer. Therefore, we have defined an eXtended Relational Algebra that allows recursive query formulation and can also be used for expressing executable schedules, and we have developed algebraic optimization strategies for recursive queries. In this paper we describe an optimization strategy that rewrites regular (in the context of formal grammars) mutually recursive queries into standard Relational Algebra and transitive closure operations. We also describe how to push selections into the resulting transitive closure operations. The reason we focus on algebraic optimization is that, in our opinion, the new generation of advanced database systems will be built starting from existing state-of-the-art relational technology, instead of building a completely new class of systems.

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Section: Discussionmentioning

confidence: 99%

Section: Transitive Closurementioning

confidence: 99%

Algebraic optimization of recursive queries

Houtsma

Apers

1992

Data & Knowledge Engineering

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“…The basic idea that underlies the disconnection set approach presented by Houtsma, Apers, and Ceri in [27,28] is best illustrated by an example. Consider a railway network connecting cities in Europe, and a question about the shortest connection between Amsterdam and Milan.…”

Section: Semantic Fragmentationmentioning

confidence: 99%

“…Complementary information is different for each type of path problem; in [27,28] the considered queries are connectivity, shortest path, and bill of material. Complementary information is different for each type of path problem; in [27,28] the considered queries are connectivity, shortest path, and bill of material.…”

Section: Semantic Fragmentationmentioning

confidence: 99%

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

Cacace

Ceri

Houtsma

1993

Distrib Parallel Databases

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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.

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“…HE capability of computing path queries is an essential feature in new database systems for many advanced applications such as navigation systems Geographical Information Systems (GIS), and computer networks [1], [2], [4], [5], [6], [11], [12], [14], [21], [22], [23], [24], [31]. For example, one of the primary functionalities of Intelligent Transportation Systems (ITS) [10], [27], [28], [32], [33] is to find routes from the current location of a vehicle to a desired destination with a minimum cost (where cost could represent travel time, shortest distance, minimal toll charges, etc.).…”

Section: Introductionmentioning

confidence: 99%

Hierarchical encoded path views for path query processing: an optimal model and its performance evaluation

Jing

Huang

Rundensteiner

1998

IEEE Trans. Knowl. Data Eng.

169

129

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Efficient path computation is essential for applications such as intelligent transportation systems (ITS) and network routing. In ITS navigation systems, many path requests can be submitted over the same, typically huge, transportation network within a small time window. While path precomputation (path view) would provide an efficient path query response, it raises three problems which must be addressed: 1) precomputed paths exceed the current computer main memory capacity for large networks; 2) disk-based solutions are too inefficient to meet the stringent requirements of these target applications; and 3) path views become too costly to update for large graphs (resulting in out-of-date query results). We propose a hierarchical encoded path view (HEPV) model that addresses all three problems. By hierarchically encoding partial paths, HEPV reduces the view encoding time, updating time and storage requirements beyond previously known path precomputation techniques, while significantly minimizing path retrieval time. We prove that paths retrieved over HEPV are optimal. We present complete solutions for all phases of the HEPV approach, including graph partitioning, hierarchy generation, path view encoding and updating, and path retrieval. In this paper, we also present an in-depth experimental evaluation of HEPV based on both synthetic and real GIS networks. Our results confirm that HEPV offers advantages over alternative path finding approaches in terms of performance and space efficiency.

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Complex transitive closure queries on a fragmented graph

Cited by 10 publications

References 15 publications

Algebraic optimization of recursive queries

Algebraic optimization of recursive queries

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

Hierarchical encoded path views for path query processing: an optimal model and its performance evaluation

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