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Count Documents

You can count the number of documents in a collection by calling one of the following methods on a Collection instance:

  • count_documents(): counts the number of documents that match a query filter. To learn more about creating query filters, see the Specify a Query guide.

  • estimated_document_count(): estimates the total number of documents in a collection by using collection metadata.

Each method returns the count as a u64 instance.

Note

If you don't pass a filter to the count_documents() method, MongoDB counts the total number of documents in the collection.

This example counts documents in the restaurants collection of the sample_restaurants database.

The following code first uses the estimated_document_count() method to count the total number of documents in the collection. Then, the example uses the count_documents() method to count the number of documents that match a query filter. The filter matches documents in which the value of the name field includes the string "Sunset":

Select the Asynchronous or Synchronous tab to see the corresponding code for each runtime:

use std::env;
use mongodb::{ bson::doc, Client, Collection };
use bson::Document;
#[tokio::main]
async fn main() -> mongodb::error::Result<()> {
let uri = "<connection string>";
let client = Client::with_uri_str(uri).await?;
let my_coll: Collection<Document> = client
.database("sample_restaurants")
.collection("restaurants");
let ct = my_coll.estimated_document_count().await?;
println!("Number of documents: {}", ct);
let ct = my_coll.count_documents(doc! { "name": doc! { "$regex": "Sunset" } }).await?;
println!("Number of matching documents: {}", ct);
Ok(())
}
use std::env;
use mongodb::{
bson::{ Document, doc },
sync::{ Client, Collection }
};
fn main() -> mongodb::error::Result<()> {
let uri = "<connection string>";
let client = Client::with_uri_str(uri)?;
let my_coll: Collection<Document> = client
.database("sample_restaurants")
.collection("restaurants");
let ct = my_coll.estimated_document_count().run()?;
println!("Number of documents: {}", ct);
let ct = my_coll
.count_documents(doc! { "name": doc! { "$regex": "Sunset" } })
.run()?;
println!("Number of matching documents: {}", ct);
Ok(())
}

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