Identifying missing indexes in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to list all indexes on the 'users' collection.

MongoDB

db.users.[1]()

Drag options to blanks, or click blank then click option'

AlistIndexes

BfindIndexes

CshowIndexes

DgetIndexes

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'findIndexes' which does not exist.

Using 'showIndexes' which is not a valid method.

Using 'getIndexes' which is incorrect.

The listIndexes() method returns all indexes on a collection in MongoDB.

2fill in blank

medium

Complete the code to check the current index usage statistics for the 'orders' collection.

MongoDB

db.orders.[1]()

Drag options to blanks, or click blank then click option'

AgetIndexStats

BindexStats

CshowIndexStats

DlistIndexStats

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'getIndexStats' which is not a MongoDB method.

Using 'showIndexStats' which does not exist.

Using 'listIndexStats' which is invalid.

The indexStats() method returns statistics about index usage on a collection.

3fill in blank

hard

Complete the code to find slow queries that might need indexes in the 'products' collection.

MongoDB

db.[1]({ millis: { $gt: 100 } })

Drag options to blanks, or click blank then click option'

AgetProfilingStatus

Bsystem.profile.find()

Cprofile.find

Dsystem.profile.find

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'getProfilingStatus' which only returns profiling settings.

Using 'system.profile.find()' which is a method call, not a property.

Using 'profile.find' which is not a valid collection name.

To find slow queries, you query the system.profile collection with find(). The correct syntax is db.system.profile.find({ millis: { $gt: 100 } }). To filter specifically for the 'products' collection, include a condition like { ns: /products$/, millis: { $gt: 100 } } (adjust db name as needed). Here, the blank expects system.profile.find.

4fill in blank

hard

Fill both blanks to create an index on the 'email' field in the 'customers' collection to improve query speed.

MongoDB

db.customers.createIndex({ [1]: [2] })

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Aemail

B1

C-1

Dusername

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'username' instead of 'email' as the field name.

Using -1 when ascending order is intended.

Swapping the field name and index order.

To create an ascending index on the 'email' field, use { email: 1 }. The field name is 'email' and the value 1 means ascending order.

5fill in blank

hard

Fill all three blanks to create a compound index on 'lastName' (ascending) and 'age' (descending) fields in the 'employees' collection.

MongoDB

db.employees.createIndex({ [1]: [2], [3]: -1 })

Drag options to blanks, or click blank then click option'

AlastName

B1

Cage

DfirstName

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'firstName' instead of 'lastName'.

Using -1 for the first field instead of 1.

Swapping the field names.

A compound index is created by specifying multiple fields. Here, 'lastName' is indexed ascending (1), and 'age' descending (-1).