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When do you need to analyze MongoDB performance?
MongoDB Performance ¶ As you develop and operate applications with MongoDB, you may need to analyze the performance of the application and its database. When you encounter degraded performance, it is often a function of database access strategies, hardware availability, and the number of open database connections.
Why is the query so slow in MongoDB?
Unfortunately, since there are only two device types, mongo needs to scan 30060 documents to find the first one that matches ‘mobile’. I assume this is some kind of web tracking, and the user’s usage pattern makes the query slow (would he switch mobile and web on a daily basis, the query would be fast).
Do you need an index for every query in Mongo?
Mongo only uses 1 index per query. So if you want to filter on 2 fields, mongo will use the index with one of the fields, but still needs to scan the entire subset. This means that basically you’ll need an index for every type of query in order to achieve the best performance.
How does the database profiler work in mongod?
The Database Profiler collects detailed information about operations run against a mongod instance. The profiler’s output can help to identify inefficient queries and operations. You can enable and configure profiling for individual databases or for all databases on a mongod instance.
How to troubleshoot MongoDB 100% CPU load?
UPD: it’s recommended to check the Monalize tool as for the automated way of issues finding https://medium.com/mongodb-cowboys/quick-scan-tool-mongodb-monalize-22888e41b1fa I guess many of you faced once the following CPU spikes on your MongoDB server:
What does slowopsamplerate do in MongoDB profiler?
See Profiler Overhead for more information on potential performance degradation. When logLevel is set to 0, MongoDB records slow operations to the diagnostic log at a rate determined by slowOpSampleRate.
What are the diagnostic log messages in MongoDB?
Starting in MongoDB 4.2, the profiler entries and the diagnostic log messages (i.e. mongod/mongos log messages) for read/write operations include: queryHash to help identify slow queries with the same query shape. planCacheKey to provide more insight into the query plan cache for slow queries.