2,353 research outputs found
Complexity of estimating multi-way join result sizes for area skewed spatial data
No full textIn a real life environment, spatial data is highly skewed. In general, there are two kinds of skews in spatial data. One is the placement skew and the other is the area skew. This paper introduces methods and the complexity of estimating the result sizes of the multi-way join for the area skewed spatial data. Especially, this paper describes the number and sort of the statistics which the optimizer should keep in order to calculate the multi-way join result size. (C) 2000 Elsevier Science B.V. All rights reserved.This research was supported by the Software Technology Enhancement Program 2000 of the Ministry of Science and Technology of Korea and the Basic Research Program (grant number 99-2-315-001-3) of the Korea Science and Engineering Foundation
Multi-way Spatial Joins Using R-Trees: Methodology and Performance Evaluation
No full textAdvances in Spatial Databases, 6th International Symposium, SSD'99, Hong Kong, China, July 20-23, 199
Spatial query optimization utilizing early separated filter and refinement strategy
No full textDue to the high complexity and large volume of spatial data, a spatial query is usually processed in two steps, called the filter step and the refinement step. However, the two-step processing of the spatial query has been considered locally in one spatial predicate evaluation at the query execution level. This paper presents query optimization strategies which exploit the two-step processing of a spatial query at the query optimization level. The first strategy involves the separation of filter and refinement steps not in the query execution phase but in the query optimization phase. As the second strategy, several refinement operations can be combined in processing a complex query if they were already separated, and as the third strategy several filter operations can also be combined. We call the optimization technique utilizing these strategies the Early Separated Filter And Refinement (ESFAR). This paper also presents an algebra, which is called the Intermediate Spatial Object Algebra (ISOA), and optimization rules for ESFAR. Through experiments using real data, we compare the ESFAR optimization technique with a traditional optimization technique which does not separate filter and refinement steps from the query optimization phase. The experimental results show that the ESFAR optimization technique generates more efficient query execution plans than the traditional one in many cases. (C) 2000 Published by Elsevier Science Ltd. All rights reserved
Heuristic approach for early separated filter and refinement strategy in spatial query optimization
No full textRecently, we proposed an optimization strategy for spatial and non-spatial mixed queries. In the strategy, the filter step and the refinement step of a spatial operator are regarded as individual algebraic operators, and are early separated at the algebraic level by the query optimizer. By doing so, the optimizer using the strategy could generate more diverse and efficient plans that the traditional optimizer. We called this optimization strategy the Early Separated Filter And Refinement (ESFAR). In this paper, we improved the cost model of the ESFAR optimizer considering the real life environment such as the LRU buffer, the clustering of the dataset, and the selectivity of the real data distribution. And we conducted a new experiment for ESFAR by comparing the optimization result generated by the new cost model and the actual execution result using real data. The experimental result showed that our cost model is accurate and our ESFAR optimizer estimates the costs of execution plans well. Since the ESFAR strategy has more operators and more rules than the traditional one, it consumes more optimization time. In this paper, we apply two existing heuristic algorithms, the iterative improvement (11) and the simulated annealing (SA), to the ESFAR optimizer. Additionally we propose a new heuristic algorithm to find a good initial state of 11 and SA. Through experiments, we show that the 11 and SA algorithms in the ESFAR strategy find a good sub-optimal plan in reasonable time. Mostly the heuristic algorithms find a lower cost plan in less time than the optimal plan generated by the traditional optimizer. Especially the 11 algorithm with the initial state heuristic rapidly finds a plan of a high quality. (C) 2001 Elsevier Science Inc. All rights reserved.This research was supported by the Basic Research Program
grant number 99-2-315-001-3) of the Korea Science and
Engineering Foundation
Sectoral allocation by gender of Latin American workers over the liberalization period of the 1990s
Get PDFThe recent restructuring of Latin American economies has renewed interest in the effects of trade liberalization, on labor markets, and on the gender division of labor. The author does not attempt to establish casuality between economic reforms, and the types of jobs that men and women hold. Instead, she provides a detailed description of the trends in male, and female formal, and informal sector participation during the economic reform period in Argentina, Brazil, and Costa Rica. The author first compares the gender composition of the formal, informal wage, and self-employment sectors in a year before reforms (1988 for Argentina, 1989 for Brazil, and Costa Rica), and a year after reforms implementation (1997 for Argentina, 1995 for Brazil and Costa Rica). Although women continued to be more likely than men to work in the informal wage sector, there is no trend of"masculinization"or"feminization"of the informal sector, or any other. Instead, in Argentina men have overtaken women as the most prevalent workers in the informal wage sector, while in Brazil, the opposite has occurred (as men move into self-employment). In Costa Rica there have been no statistical, observable changes. The author then considers the distribution across sectors within each gender group, to identify whether men, and women are more likely to select different sectors in the post-reform period relative to the pre-reform period. Among both men, and women in all three countries (except Brazilian men), workers have become more likely to hold informal wage jobs, and less likely to hold formal sector jobs. Trends in human capital accumulation explain these changes for both men, and women, while changes in gender roles, primarily in homecare and marriage, do not seem to have an effect.Health Monitoring&Evaluation,Labor Policies,Population&Development,Public Health Promotion,Environmental Economics&Policies,Health Monitoring&Evaluation,Environmental Economics&Policies,Population&Development,Banks&Banking Reform,Work&Working Conditions
Spatial Query Processing Using Object Decomposition Method
No full textACM CIKM 96, Rockville MD USA.This work was supported by the National Geographic
Information Systems Technology Development Project of the
Ministry of Science and Technology of Korea
Early Separation of Filter and Refinement Steps in Spatial Query Optimization
No full textDatabase Systems for Advanced Applications, 1999. Proceedings., 6th International Conference on
04/19/1999 - 04/21/1999, Hsinchu, Taiwan
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