Regex in Mongodb

Regex Operator

The Regex (Regular Expression) operator is a helpful tool in MongoDB. It allows the users to perform pattern matching in a string. The Regex operator allows searching patterns easily from the data stored in the MongoDB collections.

The syntax to use the Regex function in MongoDB is given below.

Syntax

{ <field>: { $regex: /pattern/, $options: '<options>' } }

OR

{ <field>: { $regex: 'pattern', $options: '<options>' } }

$options:

The options parameter can be used with MongoDB to customize our Regex searches in MongoDB. Some options' variables to use in Regular Expression are shown below in a tabular format.

In the following sections, we will see some examples of pattern matching. We will see one example using the Regex function and one without using the Regex function to see the differences between them.

Pattern Matching without Regex Operator

This section will show an example of pattern matching in MongoDB without using the Regex operator.

This blog will use my database and the below collection to run MongoDB queries.
 

Database

db.users.insertMany([
{
	name: "Rahul",
	age: 30,
	email: "rahul@gmail.com",
	status: "active"
},
{
	name: "Raghav",
	age: 25,
	email: "raghav@gmail.com",
	status: "inactive"
},
{
	name: "Priya",
	age: 40,
	email: "priya@gmail.com",
	status: "active"
}
])

We need to follow the following steps to search patterns in MongoDB without Regex.

First, we need to state the field name we want to perform pattern searching. Then we must clearly state the pattern we wish to search in the string. For example, if we need to find a line containing Ra in the name field, we must follow the following syntax.

Syntax

db.users.find({name:/Ra/})

Output

Explanation

Since both "Rahul" and "Raghav" have the string Ra present in them, we get two objects in the console.

Pattern Matching with Regex Operator

In this section, we will look at the method of pattern matching using the Regex Operator.

Database

db.users.insertMany([
{
	name: "Rahul",
	age: 30,
	email: "rahul@gmail.com",
	status: "active"
},
{
	name: "Raghav",
	age: 25,
	email: "raghav@gmail.com",
	status: "inactive"
},
{
	name: "Priya",
	age: 40,
	email: "priya@gmail.com",
	status: "active"
}
])

Let's say we want to find an entry containing the string "Rahul" in the name field, but the name starts with the string "Rahul".

Syntax

db.users.find({ name: { $regex: '^Rahul' } })

Output

Explanation

Since only the entry "Rahul" starts with the string rahul, we only get a single entry as a result.

Frequently Asked Questions

How can we perform a case-insensitive search using Regex in MongoDB?

To perform a case-insensitive search using Regex, we can set the "$options" parameter to "i." By setting the options parameter to "i," we can perform a case-insensitive search using Regex in MongoDB.

How can we escape special characters in Regex patterns?

Like most programming languages like C and C++, we can use the backslash symbol ("\") to escape special characters in regex patterns. We can place the backslash before the unique character to escape special characters in Regex.

What are the limitations of Regex in MongoDB?

The regex function is resource intensive and requires a lot of computational power for large datasets and patterns. Hence, we should consider these limitations while using Regex functions in MongoDB.

Conclusion

In this article, we discussed the Regex Operator in MongoDB. We discussed MongoDB and the Regex operator in brief. We also discussed pattern matching examples, one using the Regex operator and one without using the Regex operator. In the end, we concluded by discussing some frequently asked questions.

So now that you know about Regex in MongoDB, you can refer to similar articles.
 

• Introduction to Mongodb
   
• Query and Projection Operators in MongoDB
   
• Mongodb Operators
   

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