Regex queries in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of using regex queries in MongoDB?

Regex queries in MongoDB are used to search for documents where a string field matches a specific pattern, allowing flexible and partial text matching.

beginner

How do you write a basic regex query in MongoDB to find documents where the 'name' field starts with 'A'?

Use the query: { name: { $regex: '^A' } } which matches any 'name' starting with the letter 'A'.

beginner

What option do you add to a MongoDB regex query to make it case-insensitive?

Add the option '$options: "i"' to the regex query. For example: { name: { $regex: 'abc', $options: 'i' } } matches 'abc', 'Abc', 'ABC', etc.

intermediate

Explain the difference between using $regex and $text in MongoDB queries.

$regex matches string patterns using regular expressions, good for flexible pattern matching. $text searches text indexes for words or phrases, optimized for full-text search but less flexible for patterns.

intermediate

What is a potential performance consideration when using regex queries in MongoDB?

Regex queries that do not start with a fixed prefix can cause full collection scans, which are slow. Using anchored regex (like '^pattern') helps MongoDB use indexes and improves performance.

Which MongoDB operator is used to perform regex pattern matching?

A $regex

B $text

C $match

D $search

The $regex operator is used to match string fields against regular expression patterns.

How do you make a regex query case-insensitive in MongoDB?

A Add $options: 'i'

B Add $case: true

C Use $text instead

D Use $ignoreCase: true

Adding $options: 'i' makes the regex match case-insensitive.

What does the regex pattern '^abc' match in MongoDB?

A Strings ending with 'abc'

B Strings starting with 'abc'

C Strings containing 'abc' anywhere

D Strings exactly equal to 'abc'

The '^' anchors the pattern to the start of the string.

Which of the following is a performance tip for regex queries in MongoDB?

A Use unanchored regex for faster queries

B Avoid using indexes

C Always use $text instead of $regex

D Use anchored regex patterns starting with '^'

Anchored regex patterns allow MongoDB to use indexes and improve query speed.

What is the difference between $regex and $text in MongoDB?

A They are the same

B $regex is faster than $text

C $regex matches patterns; $text searches text indexes

D $text uses regex internally

$regex matches string patterns; $text searches full-text indexes for words or phrases.

Describe how to write a MongoDB query using regex to find documents where a field contains a specific substring, ignoring case.

Think about how to match anywhere in the string and ignore uppercase/lowercase differences.

Explain why using unanchored regex patterns in MongoDB queries might affect performance and how to improve it.

Consider how MongoDB uses indexes with regex patterns.