BSON data types overview in MongoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this BSON document query?

Given a MongoDB collection with documents containing a field value of type Int32, what will be the output of this query?

db.collection.find({ value: { $type: 16 } })

Note: $type: 16 filters documents where value is of BSON type Int32.

MongoDB

db.collection.find({ value: { $type: 16 } })

A Returns documents where 'value' is a 32-bit integer (Int32).

B Returns documents where 'value' is a 64-bit integer (Int64).

C Returns documents where 'value' is a double (floating point).

D Returns documents where 'value' is a string.

💡 Hint

Check the BSON type number for Int32 in MongoDB documentation.

In MongoDB, BSON type 16 corresponds to Int32. The query filters documents where 'value' is exactly a 32-bit integer.

🧠 Conceptual

intermediate

Which BSON data type is used to store date and time?

In BSON, which data type is used to store date and time values?

A Date

B Timestamp

C String

D ObjectId

💡 Hint

Think about the type that stores calendar dates and times.

The BSON 'Date' type stores date and time as milliseconds since the Unix epoch.

📝 Syntax

advanced

Identify the BSON type code for a 64-bit integer

Which BSON type number corresponds to a 64-bit integer (Int64) in MongoDB?

A 16

B 18

C 1

D 2

💡 Hint

Int32 is 16, double is 1, string is 2.

BSON type 18 represents Int64 (64-bit integer).

🔧 Debug

advanced

Why does this query return no results?

A user runs this query to find documents with a field score of type double:

db.collection.find({ score: { $type: 1 } })

But no documents are returned, even though some documents have score as a floating-point number. What is the most likely reason?

A The query syntax is incorrect; $type expects a string, not a number.

B The collection is empty.

C The <code>score</code> field is stored as Int32, not double.

D The <code>score</code> field is stored as string, not double.

💡 Hint

Check the actual BSON type of the score field in documents.

If score is stored as a string, filtering by $type:1 (double) returns no matches.

❓ optimization

expert

Optimizing queries filtering by BSON type

You want to optimize a MongoDB query that filters documents by the BSON type of a field data. Which approach is the most efficient for large collections?

A Use <code>{ data: { $exists: true } }</code> and then check type in application.

B Use <code>{ $where: function() { return typeof this.data === 'number'; } }</code>.

C Use <code>{ data: { $type: <type_number> } }</code> with an index on <code>data</code>.

D Scan all documents and filter in application code after fetching.

💡 Hint

Indexes help queries run faster when used properly.

Using $type with an index on the field allows MongoDB to efficiently filter documents by BSON type.