In MongoDB, the explain
operation is used to return information about the execution of a query. This method is essential for understanding and optimizing query performance within MongoDB collections.
db.collection.explain(verbosity).find(query)
The explain
method takes a verbosity
parameter to specify the level of detail in the output and returns information about the execution of a query.
Let's look at some examples of how to use the explain
method in the programGuru
collection in MongoDB:
db.programGuru.explain().find({ age: { $gt: 30 } })
This command returns information about the execution of a query that retrieves documents where the age
is greater than 30.
db.programGuru.explain("queryPlanner").find({ age: { $gt: 30 } })
This command returns query planning information for a query that retrieves documents where the age
is greater than 30.
db.programGuru.explain("executionStats").find({ age: { $gt: 30 } })
This command returns query execution statistics for a query that retrieves documents where the age
is greater than 30.
db.programGuru.explain("allPlansExecution").find({ age: { $gt: 30 } })
This command returns detailed execution information for all query plans for a query that retrieves documents where the age
is greater than 30.
Let's go through a complete example that includes switching to a database, creating a collection, inserting documents, and using the explain
method to analyze a query.
This step involves switching to a database named myDatabase
.
use myDatabase
In this example, we switch to the myDatabase
database.
This step involves creating a new collection named programGuru
in the myDatabase
database.
db.createCollection("programGuru")
Here, we create a collection named programGuru
.
This step involves inserting documents into the programGuru
collection.
db.programGuru.insertMany([
{ name: "John Doe", age: 30, email: "john.doe@example.com" },
{ name: "Jane Smith", age: 25, email: "jane.smith@example.com" },
{ name: "Jim Brown", age: 35, email: "jim.brown@example.com" }
])
We insert multiple documents into the programGuru
collection.
This step involves using the explain
method to analyze the execution of a query in the programGuru
collection.
db.programGuru.explain().find({ age: { $gt: 30 } })
We return information about the execution of a query that retrieves documents where the age
is greater than 30.
db.programGuru.explain("queryPlanner").find({ age: { $gt: 30 } })
We return query planning information for a query that retrieves documents where the age
is greater than 30.
db.programGuru.explain("executionStats").find({ age: { $gt: 30 } })
We return query execution statistics for a query that retrieves documents where the age
is greater than 30.
db.programGuru.explain("allPlansExecution").find({ age: { $gt: 30 } })
We return detailed execution information for all query plans for a query that retrieves documents where the age
is greater than 30.
The MongoDB explain
operation is crucial for understanding and optimizing query performance. Understanding how to use this method allows you to analyze and improve the efficiency of your queries, ensuring optimal performance within MongoDB collections.