Document size and growth patterns in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to find the size of a document in bytes.

MongoDB

db.collection.findOne({ _id: 1}).[1]()

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Asize

Bbsonsize

CObject.bsonsize

DgetSize

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'size' or 'getSize' which are not valid methods.

Trying to call bsonsize directly on the document.

The Object.bsonsize() method returns the size of a document in bytes in MongoDB.

2fill in blank

medium

Complete the code to calculate the average document size in a collection.

MongoDB

db.collection.aggregate([{ $group: { _id: null, avgSize: { $avg: { $[1]: "$${ROOT}" } } } }])

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Alength

Bsize

CobjectSize

DbsonSize

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent operators like $size or $length in aggregation for document size.

Confusing field size with document size.

The $bsonSize operator calculates the BSON size of each document, which can be averaged.

3fill in blank

hard

Fix the error in the code to correctly measure document size growth over time.

MongoDB

db.collection.find().forEach(doc => print(doc._id, Object.[1](doc)))

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Absonsize

BbsonSize

Cbson_size

DbsonSizeOf

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect casing like 'bsonsize' or 'bson_size'.

Trying to call a non-existent method.

The correct method name is Object.bsonSize() with a capital 'S'.

4fill in blank

hard

Fill both blanks to create a query that finds documents larger than 1KB.

MongoDB

db.collection.find({ $where: function() { return Object.[1](this) [2] 1024; } })

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AbsonSize

B>

C<

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' causing wrong filtering.

Using 'size' instead of 'bsonSize' method.

Use Object.bsonSize(this) to get document size and compare if it's greater than 1024 bytes.

5fill in blank

hard

Fill all three blanks to create a map-reduce that sums document sizes by category.

MongoDB

var map = function() { emit(this.[1], Object.[2](this)); };
var reduce = function(key, values) { return Array.[3](values, (a, b) => a + b, 0); };
db.collection.mapReduce(map, reduce, { out: 'sizeByCategory' });

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Acategory

BbsonSize

Creduce

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong field name or method names.

Using 'length' instead of 'reduce' for summing.

The map emits the category field and document size using Object.bsonSize(). The reduce uses Array.reduce() to sum sizes.