基于函数依赖的导出关系候选码计算  

Candidate Code Calculation of Derived Relation Based on Functional Dependencies

作　　者：黎章海 潘久辉[1] 

机构地区：[1]暨南大学信息科学技术学院,广州510632

出　　处：《计算机工程》2016年第5期60-65,共6页Computer Engineering

基　　金：广东省自然科学基金资助项目(S2012010008831;2015A030310208);广东省教育部产学研结合基金资助项目(2007B090400095)

摘　　要：基于函数依赖的候选码计算在基于压缩策略的快照差分算法、数据一致性检测、数据不一致修复、数据完整性约束等方面有重要的作用。分析选择、并、差、笛卡尔积等基本运算的函数依赖保持性,得出导出关系候选码与原准基础关系候选码的关系,针对投影、广义投影、笛卡尔积和聚集运算候选码可能存在冗余属性的情况,给出相应的算法优化组成候选码的属性。提出一种递归算法对给定的导出关系求出其候选码,运用快照差分算法进行实验,结果表明,运用该算法可以提高增量计算的运行效率。Candidate code calculation based on the functional dependencies has important uses in many aspects, such as in the snapshot differential algorithms based on the strategy of compression, in the data consistency inspection, in the data inconsistency repairmen and in the data integrity constraints. This paper discusses and analyzes the retaining ability of functional dependence for several basic operations such as selecting, excepting, unions and cartesian product. A conclusion on the relationship between the candidate code of derived relation and the candidate code of the original basic relations is presented. It proposes a corresponding algorithm to optimize the size of candidate attributes for projection,the generalized projection, cartesian product and aggregation operation that may have redundant attributes in their candidate code. An algorithm is proposed that can find out the candidate code for a given derived relation, and experiments are conducted applying into the snapshot differential algorithms. Results show that the algorithm can improve the efficiency of the incremental calculation.

关 键 词：候选码计算 导出关系 函数依赖 快照差分 一致性 

分 类 号：TP311[自动化与计算机技术—计算机软件与理论]