Managing risk and uncertainty in query optimization

管理查询优化中的风险和不确定性

• 批准号: 341812-2007
• 负责人: Yu, Xiaohui
• 金额: $ 1.24万
• 依托单位: York University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2010
• 资助国家: 加拿大
• 起止时间: 2010-01-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=458592
• 关键词: Managing; risk; uncertainty; query; optimization

The query optimizer, as one of the most important and most complex database system components, is key to the management of large databases. Its major task, query optimization, is to choose the best way to execute a query. Often there are several different ways (execution plans) to perform a given query, which might differ in the indices used, the orders of operators executed, etc., but all lead to the same correct result. The query optimizer generates and examines the candidate execution plans, and makes the decision as to which plan to follow for execution. The quality of the optimizer is very important, because costs of plans can vary dramatically and choosing a bad plan might result in extremely poor performance.

查询优化器作为数据库系统中最重要、最复杂的组件之一，是管理大型数据库的关键。它的主要任务，查询优化，是选择执行查询的最佳方式。通常有几种不同的方法（执行计划）来执行给定的查询，这些方法可能在使用的索引、执行操作符的顺序等方面有所不同，但都会导致相同的正确结果。查询优化器生成并检查候选执行计划，并决定按照哪个计划执行。优化器的质量非常重要，因为计划的成本可能变化很大，选择一个糟糕的计划可能会导致极其糟糕的性能。