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MongoDB - Regular Expression

Regular Expressions are commonly used in programming languages to search for patterns or words within strings. MongoDB supports regular expressions for string pattern matching using the $regex operator, based on PCRE (Perl Compatible Regular Expression) syntax.

Using Regular Expressions​

Assume we have a document in the posts collection:

db.posts.insert({
   "post_text": "enjoy the mongodb articles on tutorialspoint",
   "tags": ["mongodb", "tutorialspoint"]
})

To search for posts containing the string "tutorialspoint" in their post_text field using a regular expression:

db.posts.find({ post_text: { $regex: "tutorialspoint" } }).pretty()

Diagram: Regular Expression Query Process​

To perform a case-insensitive search, use the optionsparameterwithvalue"options parameter with value "i" in the regex query:

db.posts.find({ post_text: { $regex: "tutorialspoint", $options: "$i" } })

Using Regex for Array Elements​

Regular expressions can also be applied to array fields, such as searching for posts with tags starting from "tutorial":

db.posts.find({ tags: { $regex: "tutorial" } })

Optimizing Regex Queries​

  • Indexed fields improve the performance of regular expression queries by using indexed values for matching.
  • Prefix expressions in regular expressions, like "^tut," optimize searches by matching strings starting with specific characters.

Table: Regex Search Options​

OptionDescription
$regexOperator for regular expression pattern matching.
$optionsOptional parameter for regex options like case insensitivity.
^Anchor for matching the start of a string.
$Anchor for matching the end of a string.