本文讨论了如何通过评估SQL查询中每返回一行数据所需的逻辑读取次数来衡量查询路径的效率。通常情况下，如果每次查询返回一行数据需要进行少于5次逻辑读取，则认为该查询路径较为优秀；若逻辑读取次数在10到15次之间，则可接受；超过15到20次则表明查询路径可能不够高效，存在改进空间。
- Access paths that lead to less than about 5 logical reads per returned row are probably good
- Access paths that lead to up to about 10-15 logical reads per returned row are probably acceptable.
- Access paths that lead to more than about 15-20 logical reads per returned row are probably ineffcient. In other words, there is probably room for improvement.
Oracle access path logical read "rules of thumb"
扫一扫
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
