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数据库条件查询的非语义等价关系建模
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作者 何培蕾 游进国 +1 位作者 王宇轩 丁家满 《小型微型计算机系统》 北大核心 2025年第6期1523-1529,共7页
在数据库中,通过识别等价查询可以减少重复计算.现有方法通常从查询的语义等价关系方面来验证等价查询,然而查询的语义等价是查询结果等价的充分非必要条件,因此,仅依据语义等价关系来判断等价查询会漏掉一些语义不等价但结果相同的查询... 在数据库中,通过识别等价查询可以减少重复计算.现有方法通常从查询的语义等价关系方面来验证等价查询,然而查询的语义等价是查询结果等价的充分非必要条件,因此,仅依据语义等价关系来判断等价查询会漏掉一些语义不等价但结果相同的查询.针对这一问题,本文面向数据库条件查询提出一种非语义等价关系模型(Non-Semantic Equivalence Relation Model,NSERM):以查询的过滤条件间的包含关系作为偏序关系构建查询格,结合查询结果相等划分得到等价类,依据等价类的凸集性质,即包含等价类上界且被下界包含的查询属于该等价类,从而直接识别或回答语义不等价但结果相同的条件查询集.所提出的模型在开源数据库PostgreSQL中实现,基于TPC-H测试集的实验结果表明,NSERM能识别非语义等价的等价查询,同时还能为数据库带来性能上的提升. 展开更多
关键词 数据库 条件查询 非语义等价 查询格 等价类
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Bitmap lattice index in road networks
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作者 Doohee Song Keun-Ho Lee Kwangjin Park 《Journal of Central South University》 SCIE EI CAS 2014年第10期3856-3863,共8页
A novel technique called the bitmap lattice index(BLI) is proposed, which combines the advantages of a wireless broadcasting environment with a road network. Existing road networks are based on the on-demand method: a... A novel technique called the bitmap lattice index(BLI) is proposed, which combines the advantages of a wireless broadcasting environment with a road network. Existing road networks are based on the on-demand method: a server's workload increases as the query request increases when a server sends a client information. To solve this problem, we propose the BLI. The BLI denotes an object and a node as 0 and 1 in the Hilbert curve(HC) map. The BLI can identify the position of a node and an object through bit information; it can also reduce the broadcasting frequency of a server by reducing the size of the index, thereby decreasing the access latency and query processing times. Moreover, the BLI is highly effective for data filtering, as it can identify the positions of both an object and a node. In a road network, if filtering is done via the Euclidean distance, it may result in an error. To prevent this, we add another validation procedure. The experiment is conducted by applying the BLI to kNN query, and the technique is assessed by a performance evaluation experiment. 展开更多
关键词 road network wireless broadcast spatial query bitmap lattice index(BLI)
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