Retrieve a Random Document in MongoDB Using $sample
How to Retrieve a Random Document from MongoDB?
To retrieve a random document from a MongoDB collection, you can use the aggregation pipeline with the $sample stage. The $sample stage allows you to select a specified number of random documents from a collection, making it ideal for scenarios where you need a randomized subset or a single random record.
Description:
In MongoDB, you can fetch a random document by using the $sample stage in an aggregation pipeline. The $sample stage randomly selects a specified number of documents from the collection, providing an efficient and easy way to retrieve a random record. This approach is particularly useful for sampling data, showing a random item, or testing purposes.
Syntax:
To get a random record from a MongoDB collection, use the following syntax:
db.<collection>.aggregate([ { $sample: { size: 1 } } ])
Explanation:
- <collection>: The collection from which you want to retrieve a random document.
- size: The number of random documents you want to return. Set size to 1 to retrieve a single random document.
Example:
Suppose you have a products collection and want to fetch a single random product document:
Code:
// Use the aggregation pipeline to retrieve one random document from the products collection
db.products.aggregate([
{ $sample: { size: 1 } } // Select a single random document
])
Explanation:
- db.products.aggregate(...)
This command initiates an aggregation pipeline on the products collection, which allows for advanced data processing and transformations. - { $sample: { size: 1 } }
The $sample stage is used to retrieve random documents. The size parameter is set to 1, indicating that we want one random document. Increasing size will fetch more random documents as a sample from the collection.
The aggregation pipeline processes this query and returns a randomly selected document from the products collection. This approach is efficient because $sample is optimized for random selection, making it suitable for large collections as well.
Additional Options:
If you need more than one random document, simply adjust the size parameter. For example, setting { size: 5 } will retrieve five random documents.
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https://w3resource.com/mongodb/snippets/how-to-retrieve-a-random-document-from-mongodb.php
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