Optimization Algorithms for Simultaneous Multidimensional Queries in OLAP Environments

Kalnis, Panos; Papadias, Dimitris

doi:10.1007/3-540-44801-2_26

Cited by 4 publications

(4 citation statements)

References 15 publications

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“…The same motivation prompted much work in simultaneous query optimization in [10] and [4], to name a few. In these works, multiple queries are merged in a very explicit way.…”

Section: Single and Multi-olap Query Optimizationmentioning

confidence: 92%

Concise descriptions of subsets of structured sets

Mendelzon¹,

Pu²

2003

Proceedings of the Twenty-Second ACM SIGMOD-SIGACT-SIGART Symposium on Principles of Database Systems

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We study the problem of economical representation of subsets of structured sets, that is, sets equipped with a set cover. Given a structured set U , and a language L whose expressions define subsets of U , the problem of Minimum Description Length in L (L-MDL) is: "given a subset V of U , find a shortest string in L that defines V ".We show that the simple set cover is enough to model a number of realistic database structures. We focus on two important families: hierarchical and multidimensional organizations. The former is found in the context of semistructured data such as XML, the latter in the context of statistical and OLAP databases. In the case of general OLAP databases, data organization is a mixture of multidimensionality and hierarchy, which can also be viewed naturally as a structured set. We study the complexity of the L-MDL problem in several settings, and provide an efficient algorithm for the hierarchical case.Finally, we illustrate the application of the theory to summarization of large result sets, (multi) query optimization for ROLAP queries, and XML queries.

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“…The same motivation prompted much work in simultaneous query optimization in [10] and [4], to name a few. In these works, multiple queries are merged in a very explicit way.…”

Section: Single and Multi-olap Query Optimizationmentioning

confidence: 92%

Concise descriptions of subsets of structured sets

Mendelzon¹,

Pu²

2003

Proceedings of the Twenty-Second ACM SIGMOD-SIGACT-SIGART Symposium on Principles of Database Systems

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“…Multi-OLAP query optimization has been considered by Liang and Orlowska [2000], Zhao et al [1998], and Kalnis and Papadias [2001]. The underlying model for an OLAP cube is relational, and they considered the very-low-level costs of physical data access such as input/output cost, table join, and table scan cost.…”

Section: Some Related Query Optimization Techniquesmentioning

confidence: 99%

“…It is important to point out that in Liang and Orlowska [2000], Zhao et al [1998], and Kalnis and Papadias [2001], the content of the dimensions is not considered by the optimizer as it is thought of as part of the database. But our computation of query expression reduction makes explicit use of the dimensional structures.…”

Section: Some Related Query Optimization Techniquesmentioning

confidence: 99%

Concise descriptions of subsets of structured sets

Mendelzon

2005

ACM Trans. Database Syst.

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We study the problem of economical representation of subsets of structured sets, which are sets equipped with a set cover or a family of preorders. Given a structured set U , and a language L whose expressions define subsets of U , the problem of minimum description length in L (L-MDL) is: "given a subset V of U , find a shortest string in L that defines V ." Depending on the structure and the language, the MDL-problem is in general intractable. We study the complexity of the MDL-problem for various structures and show that certain specializations are tractable. The families of focus are hierarchy, linear order, and their multidimensional extensions; these are found in the context of statistical and OLAP databases. In the case of general OLAP databases, data organization is a mixture of multidimensionality, hierarchy, and ordering, which can also be viewed naturally as a cover-structured ordered set. Efficient algorithms are provided for the MDLproblem for hierarchical and linearly ordered structures, and we prove that the multidimensional extensions are NP-complete. Finally, we illustrate the application of the theory to summarization of large result sets and (multi) query optimization for ROLAP queries.

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“…Most the work on view selection problem focuses on data cube operations on multidimensional datasets [10,3,20,12,14,6]. The reason is not only that this kind of operations is particularly important in On Line Analytical Processing(OLAP) queries, but also because the search space for the problem with this simplified class of queries can be easily modeled and constructed as a multidimensional lattice.…”

Section: Introductionmentioning

confidence: 99%

Computing closest common subexpressions for view selection problems

Theodoratos

Zuzarte

2006

Proceedings of the 9th ACM International Workshop on Data Warehousing and OLAP

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Selecting a set of views for materialization is a required task in many current database and data warehousing applications including the design of a data warehouse, and the maintenance of multiple materialized views. The selected views can be materialized permanently or transiently depending on the specific view selection problem. The view selection algorithms are expensive due to the size of the search space of the problem.In this paper we propose an approach for generating candidate views for materialization for view selection problems based on the definition of the input queries. We also provide rewritings of the input queries using the generated candidate views. In generating candidate views, we do not apply costbased techniques but we try to maximize the operations in the views. Subsequently, view selection algorithms can exploit problem dependent cost functions to choose among the generated candidate views. Our approach is not restricted to a specific view selection problem. Compared to a previous one, it generates views that involve more relation occurrences (or operations) and can reduce the size of the search space which can be very large. We implement our approach and we report some experimental evaluation with comparison to previous works.

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Optimization Algorithms for Simultaneous Multidimensional Queries in OLAP Environments

Cited by 4 publications

References 15 publications

Concise descriptions of subsets of structured sets

Concise descriptions of subsets of structured sets

Concise descriptions of subsets of structured sets

Computing closest common subexpressions for view selection problems

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