Change streams on databases in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to watch changes on the entire database.

MongoDB

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

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Adatabase

Bwatch

CwatchStream

Dcollection

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'collection' instead of 'database' to watch changes on the whole database.

Trying to call 'watch' directly on 'db' without specifying 'database'.

To watch changes on the whole database, use db.database.watch().

2fill in blank

medium

Complete the code to listen for change events and print them.

MongoDB

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

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Aevent

Bnext

Cdata

Dchange

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'next' or 'data' as event names instead of 'change'.

Not using quotes around the event name.

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

3fill in blank

hard

Fix the error in the code to start watching changes on a database named 'shopDB'.

MongoDB

const changeStream = client.db('[1]').watch();

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Ashop

BShopDB

CshopDB

Dshop_db

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'shop' or 'ShopDB' which do not match the exact database name.

Using underscores instead of camel case.

The database name must match exactly, including case. Here it is 'shopDB'.

4fill in blank

hard

Fill both blanks to filter change events to only 'insert' operations on the database.

MongoDB

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

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A'insert'

BfullDocument

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'true' instead of 'false' for fullDocument option.

Not quoting the operationType string.

The filter uses 'insert' for operationType, and fullDocument: false disables full document retrieval.

5fill in blank

hard

Fill all three blanks to close the change stream properly after use.

MongoDB

async function watchAndClose() {
  const changeStream = db.database.watch();
  changeStream.on('change', data => console.log(data));
  await changeStream.[1]();
  console.log('[2] closed');
  return [3];
}

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

Aclose

BChange stream

Ctrue

Dstop

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'stop' instead of 'close' to end the stream.

Returning a string instead of a boolean.

Use close() to stop the stream, print a message, and return true to indicate success.