RIA: Query Optimization for Parallel Executions

查询优化指的是为以声明性语言（以SQL为代表）提出的数据库查询选择有效的执行策略。成功的顺序处理查询优化器的设计对关系数据库系统的成功做出了重要贡献。然而，当前针对并行执行的查询优化问题的解决方案是不充分的，并且限制了数据库系统在并行机器上的潜在成功。本项目涉及并行查询优化器的设计和实现。在并行查询优化器的设计中存在两个基本挑战。首先是设计近乎精确的成本模型，预测完成执行策略的并行执行所需的时间。二是设计合理高效的搜索算法，以最小的代价搜索方案。

Query Optimization refers to the selection of an efficient execution strategy for database queries posed in declarative languages, as typified by SQL. The design of successful query optimizers for sequential processing has contributed significantly to the success of relational database systems. However, current solutions to the problem of query optimization for parallel executions are inadequate 4 and limit the potential success of database systems on parallel machines. This project is concerned with the design an implementation of parallelizing query optimizers. There are two basic challenges in the design of parallelizing query optimizers. The first is the design of near-accurate cost models that predict the time it takes to complete the parallel execution of an execution strategy. The second is the design of reasonably efficient search algorithms which search for the plan with the minimum cost.