Sort Results

Overview

In this guide, you can learn how to use the MongoDB Rust Driver to perform sort operations to specify the order of your read operation results.

Use the sort() method when building options to change the order in which read operations return documents. The sort() method tells MongoDB to order returned documents by the values of one or more fields in a certain direction. To sort returned documents by a field in ascending (lowest first) order, use a value of 1. To sort in descending (greatest first) order instead, use -1. If you do not specify a sort, MongoDB does not guarantee the order of query results.

Sample Data for Examples

The examples in this guide use the following Book struct as a model for documents in the books collection:

#[derive(Debug, Serialize, Deserialize)]
struct Book {
    name: String,
    author: String,
    length: i32,
}

The following code shows how to insert sample data into the books collection:

let uri = "connection string";
let client = Client::with_uri_str(uri).await?;
let my_coll: Collection<Book> = client.database("db").collection("books");
let books = vec![
    Book {
        id: 1,
        name: "The Brothers Karamazov".to_string(),
        author: "Dostoyevsky".to_string(),
        length: 824,
    },
    Book {
        id: 2,
        name: "Atlas Shrugged".to_string(),
        author: "Rand".to_string(),
        length: 1088,
    },
    Book {
        id: 3,
        name: "Les Misérables".to_string(),
        author: "Hugo".to_string(),
        length: 1462,
    },
    Book {
        id: 4,
        name: "A Dance with Dragons".to_string(),
        author: "Martin".to_string(),
        length: 1104,
    },
];
my_coll.insert_many(books).await?;

Methods for Sorting

You can sort results retrieved by a query, or you can sort results within an aggregation pipeline.

Chain the sort() method to the find() method to sort results retrieved by the query, as shown in the following example:

let mut cursor = my_coll
    .find(doc! {})
    // 1 for ascending order, -1 for descending order
    .sort(doc! { "author": 1 })
    .await?;
while let Some(result) = cursor.try_next().await? {
    println!("{:?}", result);
}

let find_options = FindOptions::builder()
    // 1 for ascending order, -1 for descending order
    .sort(doc! { "author": 1 })
    .skip(1)
    .build();
let mut cursor = my_coll.find(doc! {}).with_options(find_options).await?;
while let Some(result) = cursor.try_next().await? {
    println!("{:?}", result);
}

let pipeline = vec![
    doc! { "$match": {} },
    // 1 for ascending order, -1 for descending order
    doc! { "$sort": { "author": 1 } }
];
let mut cursor = my_coll.aggregate(pipeline).await?;
while let Some(result) = cursor.try_next().await? {
    println!("{:?}", result);
}

Sorting Direction

The direction of your sort can either be ascending or descending. An ascending sort orders your results from smallest to largest. A descending sort orders your results from largest to smallest.

The following list contains examples of data sorted in ascending order:

• Numbers: 1, 2, 3, 43, 43, 55, 120

• Dates: 1990-03-10, 1995-01-01, 2005-10-30, 2005-12-21

• Words (ASCII): Banana, Dill, carrot, cucumber, hummus

The following list contains examples of data sorted in descending order:

• Numbers: 100, 30, 12, 12, 9, 3, 1

• Dates: 2020-01-01, 1998-12-11, 1998-12-10, 1975-07-22

• Words (reverse ASCII): pear, grapes, apple, Cheese

The following subsections show how to specify these sort criteria.

let mut cursor = my_coll
    .find(doc! {})
    .sort(doc! { "name": 1 })
    .await?;
while let Some(result) = cursor.try_next().await? {
    println!("{:?}", result);
}

Book { "_id": 4, "name": "A Dance with Dragons", "author": Martin, "length": 1104 }
Book { "_id": 2, "name": "Atlas Shrugged", "author": Rand, "length": 1088 }
Book { "_id": 3, "name": "Les Miserables", "author": Hugo, "length": 1462 }
Book { "_id": 1, "name": "The Brothers Karamazov", "author": Dostoevsky, "length": 824 }

let mut cursor = my_coll
    .find(doc! {})
    .sort(doc! { "name": -1 })
    .await?;
while let Some(result) = cursor.try_next().await? {
    println!("{:?}", result);
}

Book { "_id": 1, "name": "The Brothers Karamazov", "author": Dostoevsky, "length": 824 }
Book { "_id": 3, "name": "Les Miserables", "author": Hugo, "length": 1462 }
Book { "_id": 2, "name": "Atlas Shrugged", "author": Rand, "length": 1088 }
Book { "_id": 4, "name": "A Dance with Dragons", "author": Martin, "length": 1104 }

Additional Information

To learn more about the operations mentioned in this guide, see the following:

• Specify a Query

• Retrieve Data

• Compound Operations

• Aggregation

• Skip Returned Results