November 2021
Intermediate to advanced
410 pages
12h 1m
Chinese
Content preview from MongoDB权威指南（第3版）
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
310
｜
第
18
章
> db.setProfilingLevel(1, 500)
{ "was" : 2, "slowms" : 100, "ok" : 1 }
要关闭分析器，可以将分析级别设置为
0
：
> db.setProfilingLevel(0)
{ "was" : 1, "slowms" : 500, "ok" : 1 }
将
slowms
设置为较低的值通常不是一个好主意。即使分析器处于关闭状态，
slowms
也会
对
mongod
产生影响
：因为它决定了在日志中打印慢速操作的阈值。因此，如果将
slowms
设置为
2
，那么每个耗时超过两毫秒的操作都将显示在日志中，即使分析器是关闭的。因
此，如果调低了
slowms
来分析某些东西，那么可能需要在关闭分析器之前将它重新调高。
可以使用
db.getProfilingLevel()
来查看当前的分析级别。分析级别不是持久的：重新启
动数据库会清除级别的设定值。
也有用于配置分析级别的命令行选项，即
--profile +
level
和
--slowms +
time
，但是提
升分析级别通常是临时的调试措施，而不应该长期添加到配置中。
在
MongoDB 4.2
中
，通过添加
queryHash
和
planCacheKey
字段，分析器条目和诊断日志消
息被扩展为读
/
写操作
，以帮助提高对慢查询的识别。
queryHash
字符串表示查询形状的
哈希值，并且仅依赖于查询的形状。每个查询形状都与一个
queryHash
相关联，从而更容
易突显出使用相同形状的查询。
planCacheKey
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.