Change stream pipelines for filtering in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a change stream that listens for all changes.

MongoDB

const changeStream = collection.watch([1]);

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

Anull

B{}

C[]

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using an object {} instead of an array []

Passing null or true which are invalid pipeline arguments

The watch method takes an array as the pipeline argument. An empty array [] means no filtering, so all changes are listened to.

2fill in blank

medium

Complete the code to filter change events to only include inserts.

MongoDB

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

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

A'delete'

B'update'

C'replace'

D'insert'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'update' or 'delete' which filter other change types

Forgetting to put quotes around the string

The operationType field indicates the type of change. To filter for inserts, use 'insert'.

3fill in blank

hard

Fix the error in the pipeline to filter changes where the field 'status' is 'active'.

MongoDB

const pipeline = [ { $match: { 'fullDocument.status': [1] } } ];

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

A'active'

Bactive

C"status"

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted strings causing syntax errors

Using boolean true instead of the string

String values in MongoDB queries must be quoted. So 'active' is correct.

4fill in blank

hard

Fill both blanks to filter change events for updates where the 'age' field is greater than 30.

MongoDB

const pipeline = [ { $match: { operationType: [1], 'fullDocument.age': { [2]: 30 } } } ];

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

A'update'

B'insert'

C$gt

D$lt

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'insert' instead of 'update' for operationType

Using $lt instead of $gt for greater than comparison

To filter for update events, use 'update'. To check if 'age' is greater than 30, use the MongoDB operator $gt.

5fill in blank

hard

Fill all three blanks to create a pipeline that filters for delete operations where the document's 'score' is less than 50.

MongoDB

const pipeline = [ { $match: { operationType: [1], 'fullDocument.score': { [2]: 50 }, 'ns.db': [3] } } ];

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

A'insert'

B$lt

C'myDatabase'

D'delete'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'insert' instead of 'delete' for operationType

Using $gt instead of $lt for less than comparison

Not quoting the database name

To filter delete operations, use 'delete'. To check if 'score' is less than 50, use $lt. The database name is a string, so use 'myDatabase'.