Results 291 to 300 of about 193,669 (327)
Some of the next articles are maybe not open access.
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.
Vijayshankar Raman +3 more
openaire +1 more source
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
openaire +2 more sources
Optimizing a Query by Transformation and Expansion
2017In the biomedical sector not only the amount of information produced and uploaded into the web is enormous, but also the number of sources where these data can be found. Clinicians and researchers spend huge amounts of time on trying to access this information and to filter the most important answers to a given question.
Alexander Knurr +8 more
openaire +3 more sources
Multiobjective query optimization
Proceedings of the twentieth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems, 2001The optimization of queries in distributed database systems is known to be subject to delicate trade-offs. For example, the Mariposa database system allows users to specify a desired delay-cost tradeoff (that is, to supply a decreasing function u(d), specifying how much the user is willing to pay in order to receive the query results within time d ...
Christos H. Papadimitriou +1 more
openaire +2 more sources
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 ...
Louiqa Raschid +4 more
openaire +1 more source
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 ...
Louiqa Raschid +4 more
openaire +1 more source
Query Evaluation and Optimization
2000The optimization of queries over constraint databases is aprerequisite to the use of this methodology for data intensiveapplications. It therefore constitutes a fundamental issue. In thischapter, we present some preliminary results, together with promisingdirections of research.
Grumbach, Stéphane +3 more
openaire +1 more source
Query Optimization and Execution
2014SQL Server Query Processor is perhaps the least visible and least well-known part of SQL Server. It does not expose a large set of public features, and it allows very limited control in a documented and supported way. It accepts a query as input, compiles and optimizes it to generate the execution plan, and finally executes it.
openaire +2 more sources
2006
Determining the best execution plan for a spatial query requires tools for measuring (more precisely, estimating) the number of (spatial) data items that are retrieved by a query as well as its cost, in terms of I/O and CPU effort. As in traditional databases, spatial query optimization tools include cost-based models, exploiting analytical formulae ...
Apostolos N. Papadopoulos +3 more
openaire +2 more sources
Determining the best execution plan for a spatial query requires tools for measuring (more precisely, estimating) the number of (spatial) data items that are retrieved by a query as well as its cost, in terms of I/O and CPU effort. As in traditional databases, spatial query optimization tools include cost-based models, exploiting analytical formulae ...
Apostolos N. Papadopoulos +3 more
openaire +2 more sources
2005
We propose and solve the optimal-location query in spatial databases. Given a set S of sites, a set O of weighted objects, and a spatial region Q, the optimal-location query returns a location in Q with maximum influence. Here the influence of a location l is the total weight of its RNNs, i.e.
Tian Xia, Donghui Zhang, Yang Du
openaire +2 more sources
We propose and solve the optimal-location query in spatial databases. Given a set S of sites, a set O of weighted objects, and a spatial region Q, the optimal-location query returns a location in Q with maximum influence. Here the influence of a location l is the total weight of its RNNs, i.e.
Tian Xia, Donghui Zhang, Yang Du
openaire +2 more sources
Optimizing Phylogenetic Queries for Performance
IEEE/ACM Transactions on Computational Biology and Bioinformatics, 2018The vast majority of phylogenetic databases do not support declarative querying using which their contents can be flexibly and conveniently accessed and the template based query interfaces they support do not allow arbitrary speculative queries. They therefore also do not support query optimization leveraging unique phylogeny properties.
openaire +3 more sources