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Evaluate Performance of Current Operations

The following sections describe techniques for evaluating operational performance.

Use the Database Profiler to Evaluate Operations Against the Database

MongoDB provides a database profiler that shows performance characteristics of each operation against the database. Use the profiler to locate any queries or write operations that are running slow. You can use this information, for example, to determine what indexes to create.

For more information, see Database Profiling.

Use db.currentOp() to Evaluate mongod Operations

The db.currentOp() method reports on current operations running on a mongod instance.

Use explain to Evaluate Query Performance

The cursor.explain() and db.collection.explain() methods return information on a query execution, such as the index MongoDB selected to fulfill the query and execution statistics. You can run the methods in queryPlanner mode, executionStats mode, or allPlansExecution mode to control the amount of information returned.

Example

To use cursor.explain() on a query for documents matching the expression { a: 1 }, in the collection named records, use an operation that resembles the following in the mongo shell:

db.records.find( { a: 1 } ).explain("executionStats")

For more information, see Explain Results, cursor.explain(), db.collection.explain(), and Analyze Query Performance.