基于传输代价最小原则的分布式数据库查询优化

分布式查询算法的核心部分是全局查询优化算法，将查询请求合理地优化分解为子查询任务，并尽量使子查询任务并行执行。分布式查询的优化需要权衡网络流量、响应时间、服务器负载、算法复杂性等多种因素。本着减少节点之间的数据传输量的目的，本文提出一个复杂度和延迟时间之间进行衡量的全局优化算法。本文就连接查询和复合查询进行了详细的分析，最后提出了一种基于半连接的查询优化算法，并分析了该改进算法的优缺点。

A Query Optimization Strategy for Distributed Databases Based on the Principle of Minimizing Transmission Costs

Distributed query algorithm is the core part of the overall query optimization algorithm.Inquiries request will be divided into sub-query optimization tasks reasonably and sub-tasks is to make parallel execution. Distributed query optimization need to balance network traffic, response time, server load and a variety of factors, such as the complexity of algorithms. In reducing the volume of data transmission between nodes, this paper presents a global optimization algorithm between complexity and delay time. This paper conducted a detailed analysis of complex inquiries and join inquiries. Finally, it presents a semi-join-based query optimization algorithm and its advantages and disadvantages.