bowlkasce.blogg.se - Mongo db optimizer

MongoDB offers a broad range of index types and features with Our compound index can still be used to filter queries that specify the last name only. Indexing File storage Aggregation Special collection types Question 2 (2 points) True or false: MongoDB supports horizontal scaling out.Īnalyze Query Performance, Best practices for delivering performance at scale with MongoDB. Question 1 (2 points) Which MongoDB feature can be used to enhance the performance of queries? Select one. that, to improve efficiency, the query might benefit from the use of an index. Query Optimization, These statistics can be useful in measuring if and how a query uses an index. Use hint () to support performance testing, or on some queries where you must select a field or field included in several indexes. Optimize Query Performance, To improve the performance of this query, add an ascending or a descending A covered query is a query that can be satisfied entirely using an index and does In most cases the query optimizer selects the optimal index for a specific operation however, you can force MongoDB to use a specific index using the hint () method. I have done a reasonable amount of Which MongoDB feature can be used to enhance the Performance of queries

Ask Question Asked 7 years, 10 months ago.

Use Projections to Return Only MongoDB Query Performance Analysis.

Limit the Number of Query Results to Reduce Network Demand.

Optimize Query Performance, Optimize Query Performance¶ Fortunately, MongoDB provides very handy tool which can be used to evaluate query performance: explain ("executionStats"). Analyze query performance in mongodb may became complicated if we do not really know which part should be measured. You can use this information, for example, to determine what indexes to create. Use the profiler to locate any queries or write operations that are running slow. db.collection.explain () provides information on the execution of other operations, such as db.collection.update ().Įvaluate Performance of Current Operations, MongoDB provides a database profiler that shows performance characteristics of each operation against the database. These statistics can be useful in measuring if and how a query uses an index. The cursor.explain ("executionStats") and the db.collection.explain ("executionStats") methods provide statistics about the performance of a query. all documents in the collection) to find the three matching documents. Documents Examined displays 10 to indicate that MongoDB had to scan ten documents (i.e. > db.students.find(īy executing the above statement, it can be seen that detailed query information is recorded in of number of projections on query performance MongoDB query performance analysisĪnalyze Query Performance, The Query Performance Summary shows the execution stats of the query: Index Keys Examined displays 0 to indicate that this query is not using an index.

You can use the db. () command to directly find the profiler logs whose execution time is greater than a certain limit (such as 5ms) So as long as you query the records of this collection, you can get the logs recorded by the profiler. The profile is the capped collection collection mentioned earlier. The mysql slow query log is stored on the disk, and the mongodb profiler record is directly stored in the system db.

The default time for slow query is 100ms, of course, it can also be set by the parameter slowsms. If set to 2, it means that all statements will be recorded in the log. The profiler information is saved in the system.profile table, and the current profiler level can be obtained by executing the "db.getProfilingLevel ()" command:Īs you can see in the figure above, there are three parameters in total, 0 is off, 1 is slow query, and 2 is all. The second is to execute the "db.setProfilingLevel (level)" command on the client The first is to set it directly in the startup parameters, just add -profile = level when the eggplant mongodb There are two types of profier functions: Mongodb's own profiler can easily record all time-consuming operations for easy tuning 1. In the mysql database, the slow query log is often used as the basis for optimizing the database, and mongodb still has similar functions.