Results 231 to 240 of about 198,739 (283)
Some of the next articles are maybe not open access.
Optimizing query rewriting for multiple queries
Proceedings of the Ninth International Workshop on Information Integration on the Web, 2012We present an scalable algorithm for answering multiple conjunctive queries using views. This is an important problem in query optimization, data integration and ontology-based data access. Since rewriting one conjunctive query using views is an NP-hard problem, we develop an approach where answering n queries takes less than n times the cost of ...
George Konstantinidis, José Luis Ambite
openaire +1 more source
Proceedings of the 2009 ACM SIGMOD International Conference on Management of data, 2009
Query Optimization is expected to produce good execution plans for complex queries while taking relatively small optimization time. Moreover, it is expected to pick the execution plans with rather limited knowledge of data and without any additional input from the application.
openaire +1 more source
Query Optimization is expected to produce good execution plans for complex queries while taking relatively small optimization time. Moreover, it is expected to pick the execution plans with rather limited knowledge of data and without any additional input from the application.
openaire +1 more source
Query scheduling in multi query optimization
Proceedings 2001 International Database Engineering and Applications Symposium, 2002Complex queries are becoming commonplace, with the growing use of decision support systems. Decision support queries often have a lot of common sub-expressions within each query, and queries are often run as a batch. Multi query optimization aims at exploiting common sub-expressions, to reduce the evaluation cost of queries, by computing them once and ...
A. Gupta, S. Sudarshan, S. Vishwanathan
openaire +1 more source
Algebraic query optimization for distributed top-k queries
Informatik - Forschung und Entwicklung, 2007Distributed top-k query processing is increasingly becoming an essential functionality in a large number of emerging application classes. This paper addresses the efficient algebraic optimization of top-k queries in wide-area distributed data repositories where the index lists for the attribute values (or text terms) of a query are distributed across a
Neumann, T., Michel, S.
openaire +3 more sources
ACM SIGMOD Record, 1996
The strength of commercial query optimizers like DB2 comes from their ability to select an optimal order by generating all equivalent reorderings of binary operators. However, there are no known methods to generate all equivalent reorderings for a SQL query containing joins, outer joins, and groupby aggregations.
Piyush Goel, Bala Iyer
openaire +1 more source
The strength of commercial query optimizers like DB2 comes from their ability to select an optimal order by generating all equivalent reorderings of binary operators. However, there are no known methods to generate all equivalent reorderings for a SQL query containing joins, outer joins, and groupby aggregations.
Piyush Goel, Bala Iyer
openaire +1 more source
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 ...
V. Zadorozhny +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 ...
V. Zadorozhny +4 more
openaire +1 more source
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
openaire +1 more source
Proceedings of the 3rd VLDB Workshop on In-Memory Data Mangement and Analytics, 2015
In the recent past, in-memory distributed database management systems have become increasingly popular to manage and query huge amounts of data. For an in-memory distributed database like MemSQL, it is imperative that the analytical queries run fast.
Rajkumar Sen +2 more
openaire +1 more source
In the recent past, in-memory distributed database management systems have become increasingly popular to manage and query huge amounts of data. For an in-memory distributed database like MemSQL, it is imperative that the analytical queries run fast.
Rajkumar Sen +2 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 +1 more source
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 +1 more source