Results 251 to 260 of about 2,049,708 (294)
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Journal of Algorithms, 1993
Summary: Let \(\Gamma_ 0\) be a set of \(n\) halfspaces in \(E^ d\) (where the dimension \(d\) is fixed) and let \(m\) be a parameter, \(n\leq m\leq n^{\lfloor d/2\rfloor}\). We show that \(\Gamma_ 0\) can be preprocessed in time and space \(0(m^{1+\delta}\)) (for any fixed \(\delta>0\)) so that given a vector \(c\in E^ d\) and another set \(\Gamma_ q\)
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Summary: Let \(\Gamma_ 0\) be a set of \(n\) halfspaces in \(E^ d\) (where the dimension \(d\) is fixed) and let \(m\) be a parameter, \(n\leq m\leq n^{\lfloor d/2\rfloor}\). We show that \(\Gamma_ 0\) can be preprocessed in time and space \(0(m^{1+\delta}\)) (for any fixed \(\delta>0\)) so that given a vector \(c\in E^ d\) and another set \(\Gamma_ q\)
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Multidatabase Query Optimization
Distributed and Parallel Databases, 1997A multidatabase system (MDBS) allows the users to simultaneously access heterogeneous, and autonomous databases using an integrated schema and a single global query language. The query optimization problem in MDBSs is quite different from the query optimization problem in distributed homogeneous databases due to schema heterogeneity and autonomy of ...
Cem Evrendilek +3 more
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Parallelizing query optimization
Proceedings of the VLDB Endowment, 2008Many commercial RDBMSs employ cost-based query optimization exploiting dynamic programming (DP) to efficiently generate the optimal query execution plan. However, optimization time increases rapidly for queries joining more than 10 tables.
Wook-Shin Han +4 more
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Semantic query optimization for object queries
1995Semantic query optimization is an approach to query optimization that utilizes semantic knowledge to reformulate a query into one that would generate the same set of answers in a more efficient way. The semantic query optimization becomes more important in OODB systems where object queries are complex due to the presence of object-oriented concepts ...
Young-Whun Lee, Suk I. Yoo
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Progressive Query Optimization for Federated Queries
2006Database Management Systems (DBMS) perform query plan selection by mathematically modeling the execution cost of candidate execution plans and choosing the cheapest query execution plan (QEP) according to that cost model. The cost model requires accurate estimates of the sizes of intermediate results of all steps in the QEP.
Stephan Ewen +3 more
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Proceedings of 16th International Conference on Data Engineering (Cat. No.00CB37073), 2002
We demonstrate a Web Query Optimizer (WQO) within an architecture of mediators and wrappers, for WebSources of limited capability in a wide area environment. The WQO has several innovative features, including a CBR (capability based rewriting) tool, an enhanced randomized relational optimizer extended to a Web environment, and a WebWrapper cost model ...
Vladimir Zadorozhny +4 more
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We demonstrate a Web Query Optimizer (WQO) within an architecture of mediators and wrappers, for WebSources of limited capability in a wide area environment. The WQO has several innovative features, including a CBR (capability based rewriting) tool, an enhanced randomized relational optimizer extended to a Web environment, and a WebWrapper cost model ...
Vladimir Zadorozhny +4 more
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Query Optimization for Database-Returning Queries
Proceedings of the ACM on Management of DataRecently, the novel concept of database-returning SQL queries (DRQs) was introduced. Instead of a single, (potentially) denormalized result table, DRQs return an entire subdatabase with a single SQL query. This subdatabase represents a subset of the original database, reduced to the relations, tuples, and attributes that contribute
Simon Rink, Jens Dittrich
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Optimization of schemaSQL queries
Proceedings 2001 International Database Engineering and Applications Symposium, 2002We study the optimization of schemaSQL and schemaSQL-like languages. Our starting point is an extended relational algebra which can be used to implement schemaSQL and similar languages. We study transformation (rewrite) rules for the extended algebra which are used in a prototype cost-based optimizer for the rewriting of expressions into more efficient
Keir B. Davis, Fereidoon Sadri
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Bringing order to query optimization [PDF]
ACM SIGMOD Record, 2002 A variety of developments combine to highlight the need for respecting order when manipulating relations. For example, new functionality is being added to SQL to support OLAP-style querying in which order is frequently an important aspect. The set- or multiset-based frameworks for query optimization that are currently being taught to database students ...
Giedrius Slivinskas +2 more
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2009
Complex queries are becoming commonplace with the growing use of decision support systems. These complex queries often have a lot of common sub-expressions, either within a single query, or across multiple such queries. The focus of this work is to speed up query execution by exploiting these common subexpressions.
Prasan Roy, S. Sudarshan
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Complex queries are becoming commonplace with the growing use of decision support systems. These complex queries often have a lot of common sub-expressions, either within a single query, or across multiple such queries. The focus of this work is to speed up query execution by exploiting these common subexpressions.
Prasan Roy, S. Sudarshan
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