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semi-joins
相关语句
  半连接
     In the paper [1] a solution using semi-joins for tree queries is provided;
     在文献中,已经提供了用半连接对树查询的求解手段;
短句来源
  “semi-joins”译为未确定词的双语例句
     USING SEMI-JOINS TO REALIZE JOINS AND MIXED-SEMI(?)JOINS
     用半连接实现连接及广义半连接
短句来源
     An efficient optimization algorithm for distributed query, i.e., WPERF+, is presented in this paper. The advantages of W semi- joins and PERF joins have been combined into the WPERF+, and greatly enhanced the performance of W semi-joins and PERF joins.
     本文展示了一种新的分布式查询的算法,即WPERF+连接算法,它结合了W算法和PERF算法的特点,进一步强化了W算法和PERF的性能。
短句来源
  相似匹配句对
     On Mathematical Semi -otics
     数学符号学初探
短句来源
     Semi-analytical Function
     半解析函数
短句来源
     SEMI—SUPERNILPOTENT RADICALS
     半超幂零根
短句来源
     Semi Bianalytic Functions
     半双解析函数
短句来源
     On Philosophy Joins Economics
     论哲学与经济学的联袂
短句来源
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  semi-joins
The algorithm extends the SDD-1algorithm by considering local processing cost as well as communication cost.Whereas the SDD-1 algorithm only uses semi-joins to reduce communication cost,the algorithm reduces it with joins as well.
      
The inexpensive query strategy is obtained primarily by computing the most profitable semi-joins and by determining the best sequence of join operations per processing site.
      
Similar to semi-joins in distributed query processing, hash filters can be applied to eliminate non-matching tuples from joining relations before the execution of a join, thus reducing the join cost.
      


In DDBS query processing, Semi-Join is often used to realize joins of relations distributed among different sites. This method may reduce communication cost in performing joins. This paper provides an efficient algorithm to perform this kind of operations. In comparison wish the existing methods, our algorithm has the following advantages.

在分布式数据库系统的查询处理中,普遍采用半连接的方法实现分布在不同站点间的关系的连接,以降低通讯开销。本文提出一种实现这类运算的方案,同以前的方案相比,该方案具有如下优点: (1) 有一个简单实用的判据J,可判定同直接进行连接运算相比较,这一方法是否确有收益及收益的大小。(2) 可在实际开始数据传送之前就决定下一步是用半连接进行连接的预处理呢还是直接进行连接;这是以J为依据的(因此J是一个可进行及时指导的判据),可避免不必要的开销,提高查询处理的效率。本文对半连接运算进行了推广,给出了广义半连接的概念,及有关的性质,用以有效地处理更广泛的查询。例如在连接运算上的选择运算,这为解决S-P-J表达式(选择-投影-连接表达式)型查询提供了合理的基础。

The query processing in the distributed database systems is compre-hensively summarized.This paper shows that using HASHING method for thereduction of semi-join communication cost is beneficial.It also introduces arelational operator semi-join with ordinal numbers.By means of it,the fullreduction S~* of cyclic queries can be always obtained.

本文较全面地总结了分布式数据库系统的查询处理,并提出用HASHING 方法减少半连接通讯的开销是有利的。本文引进了带序号的半连接关系操作,用它总可以求得有回路查询的全缩减S。

This paper discusses the primary concepts and methods related to distributed query processing. The paper also shows the characteristics of query using semi-join to fully reduce relations occurring in the query qualification and brings out a method of cost measurement Query processing algorithm based on semi-join is divided into three phases: copy identification phase, reduction phase and assembly phase. We also raise the characteristics of tree query and cyclic query, tree query recognition algorithm and transformation...

This paper discusses the primary concepts and methods related to distributed query processing. The paper also shows the characteristics of query using semi-join to fully reduce relations occurring in the query qualification and brings out a method of cost measurement Query processing algorithm based on semi-join is divided into three phases: copy identification phase, reduction phase and assembly phase. We also raise the characteristics of tree query and cyclic query, tree query recognition algorithm and transformation algorithm from cyclic query to tree query. Moreover, the paper approaches the optimal strategies of simple query and tree query, as well as heuristics algorithms based on semijoins.

本文讨论了分布式查询处理中所涉及的主要概念和方法.文中给出了能用半连接运算完全简化出现在查询限制条件中的关系的查询特征.文中将基于半连接运算的查询处理算法分成三个阶段:副本标识阶段、简化阶段和综合阶段.我们讨论了树查询和循环查询的特征、树查询的识别和循环查询到树查询的转换.此外,本文还对简单查询和树查询的最佳策略以及半连接的启发式算法进行了讨论.

 
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