Use cases for change streams in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to watch for changes in the 'orders' collection.

MongoDB

const changeStream = db.collection('orders').[1]();

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

Ainsert

Bfind

Caggregate

Dwatch

Attempts:

3 left

💡 Hint

Common Mistakes

Using find() instead of watch() to listen for changes.

Trying to use aggregate() without a pipeline for change streams.

The watch() method starts a change stream to listen for changes in the collection.

2fill in blank

medium

Complete the code to filter change events for only 'insert' operations.

MongoDB

const pipeline = [ { $match: { 'operationType': [1] } } ];

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

A'delete'

B'insert'

C'update'

D'replace'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'update' or 'delete' instead of 'insert' for filtering inserts.

Forgetting to put quotes around the operation type.

The operationType field filters events. To watch inserts, use 'insert'.

3fill in blank

hard

Fix the error in the code to properly handle change stream events.

MongoDB

changeStream.on('[1]', next => { console.log(next); });

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

Achange

Berror

Cdata

Dupdate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'update' which is an operation type, not an event name.

Using 'error' which listens for errors, not changes.

The event name to listen for change notifications is 'change'.

4fill in blank

hard

Fill both blanks to create a change stream that watches only 'delete' operations on the 'products' collection.

MongoDB

const pipeline = [ { $match: { 'operationType': [1] } } ]; const changeStream = db.collection([2]).watch(pipeline);

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

A'delete'

B'insert'

C'orders'

D'products'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'insert' instead of 'delete' for operationType.

Watching the wrong collection name.

To watch deletes on 'products', filter by 'delete' and watch the 'products' collection.

5fill in blank

hard

Fill all three blanks to create a change stream that watches 'update' operations and prints the updated fields.

MongoDB

const pipeline = [ { $match: { 'operationType': [1] } } ]; const changeStream = db.collection('users').watch(pipeline); changeStream.on('[2]', change => { console.log(change.updateDescription.[3]); });

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

A'update'

B'change'

CupdatedFields

D'insert'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'insert' instead of 'update' for operationType.

Listening on 'insert' event instead of 'change'.

Accessing wrong property instead of 'updatedFields'.

Filter for 'update' operations, listen on the 'change' event, and access updatedFields to see changed fields.