Iterative Query Processing based on Unified Optimization Techniques

2019 ◽  
Author(s):  
Kisung Park ◽  
Hojin Seo ◽  
Mostofa Kamal Rasel ◽  
Young-Koo Lee ◽  
Chanho Jeong ◽  
...  
Keyword(s):  
Query Processing ◽  
Optimization Techniques

Query Processing and Optimization Techniques over Streamed Fragmented XML

2008 ◽  
Vol 11 (3) ◽  
pp. 339-359 ◽  
Author(s):  
Guoren Wang ◽  
Huan Huo ◽  
Donghong Han ◽  
Xiaoyun Hui
Keyword(s):  
Query Processing ◽  
Optimization Techniques ◽  
Query Processing And Optimization

Elasticity in Cloud Databases and Their Query Processing

2013 ◽  
Vol 9 (2) ◽  
pp. 1-20 ◽  
Author(s):  
Goetz Graefe ◽  
Anisoara Nica ◽  
Knut Stolze ◽  
Thomas Neumann ◽  
Todd Eavis ◽  
...  
Keyword(s):  
Query Processing ◽  
Query Optimization ◽  
High Availability ◽  
Optimization Techniques ◽  
Cloud Services ◽  
Materialized Views ◽  
Short Period ◽  
Cloud Databases ◽  
Elastic Data ◽  
Entire Dataset

A central promise of cloud services is elastic, on-demand provisioning. The provisioning of data on temporarily available nodes is what makes elastic database services a hard problem. The essential task that enables elastic data services is bringing a node and its data up-to-date. Strategies for high availability do not satisfy the need in this context because they bring nodes online and up-to-date by repeating history, e.g., by log shipping. Nodes must become up-to-date and useful for query processing incrementally by key range. What is wanted is a technique such that in a newly added node, during each short period of time, an additional small key range becomes up-to-date, until eventually the entire dataset becomes up-to-date and useful for query processing, with overall update performance comparable to a traditional high-availability strategy that carries the entire dataset forward without regard to key ranges. Even without the entire dataset being available, the node is productive and participates in query processing tasks. The authors’ proposed solution relies on techniques from partitioned B-trees, adaptive merging, deferred maintenance of secondary indexes and of materialized views, and query optimization using materialized views. The paper introduces a family of maintenance strategies for temporarily available copies, the space of possible query execution plans and their cost functions, as well as appropriate query optimization techniques.

On the Efficiency of Querying and Storing RDF Documents

2011 ◽  
pp. 354-385
Author(s):  
Maria-Esther Vidal ◽  
Amadís Martínez ◽  
Edna Ruckhaus ◽  
Tomas Lampo ◽  
Javier Sierra
Keyword(s):  
Query Processing ◽  
Execution Time ◽  
Time Complexity ◽  
Low Cost ◽  
Data Access ◽  
Optimization Techniques ◽  
Experimental Results ◽  
Access Time ◽  
Alternative Representation ◽  
Rdf Data

In the context of the Semantic Web, different approaches have been defined to represent RDF documents, and the selected representation affects storage and time complexity of the RDF data recovery and query processing tasks. This chapter addresses the problem of efficiently querying and storing RDF documents, and presents an alternative representation of RDF data, Bhyper, which is based on hypergraphs. Additionally, access and optimization techniques to efficiently execute queries with low cost, are defined on top of this hypergraph based representation. The chapter’s authors have empirically studied the performance of the Bhyper based techniques, and their experimental results show that the proposed hypergraph based formalization reduces the RDF data access time as well as the space needed to store the Bhyper structures, while the query execution time of state-the-of-art RDF engines can be sped up by up to two orders of magnitude.

Review on the aerodynamics of intermediate compressor duct

2020 ◽  
Vol 14 (4) ◽  
pp. 7446-7468
Author(s):  
Manish Sharma ◽  
Beena D. Baloni
Keyword(s):  
High Pressure ◽  
Pressure Loss ◽  
Flow Analysis ◽  
Outer Wall ◽  
Optimization Techniques ◽  
Optimum Pressure ◽  
Research Areas ◽  
Static Pressure Distribution ◽  
High Pressure Compressor ◽  
Pressure Compressor

In a turbofan engine, the air is brought from the low to the high-pressure compressor through an intermediate compressor duct. Weight and design space limitations impel to its design as an S-shaped. Despite it, the intermediate duct has to guide the flow carefully to the high-pressure compressor without disturbances and flow separations hence, flow analysis within the duct has been attractive to the researchers ever since its inception. Consequently, a number of researchers and experimentalists from the aerospace industry could not keep themselves away from this research. Further demand for increasing by-pass ratio will change the shape and weight of the duct that uplift encourages them to continue research in this field. Innumerable studies related to S-shaped duct have proven that its performance depends on many factors like curvature, upstream compressor’s vortices, swirl, insertion of struts, geometrical aspects, Mach number and many more. The application of flow control devices, wall shape optimization techniques, and integrated concepts lead a better system performance and shorten the duct length.  This review paper is an endeavor to encapsulate all the above aspects and finally, it can be concluded that the intermediate duct is a key component to keep the overall weight and specific fuel consumption low. The shape and curvature of the duct significantly affect the pressure distortion. The wall static pressure distribution along the inner wall significantly higher than that of the outer wall. Duct pressure loss enhances with the aggressive design of duct, incursion of struts, thick inlet boundary layer and higher swirl at the inlet. Thus, one should focus on research areas for better aerodynamic effects of the above parameters which give duct design with optimum pressure loss and non-uniformity within the duct.

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