Get and batch get

.one(id) reads one document by its ID, and returns None when it does not exist. .batch(ids) reads several documents in one request, and streams each ID with its document or None:

use firestore::*;
use futures::stream::BoxStream;
use serde::{Deserialize, Serialize};
#[derive(Debug, Clone, Deserialize, Serialize)]
struct MyTestStructure {
    some_id: String,
}
const TEST_COLLECTION_NAME: &str = "test";
async fn example(db: FirestoreDb, my_struct: MyTestStructure) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
let find_it_again: Option<MyTestStructure> = db
    .fluent()
    .select()
    .by_id_in(TEST_COLLECTION_NAME)
    .obj()
    .one(&my_struct.some_id)
    .await?;

let object_stream: BoxStream<(String, Option<MyTestStructure>)> = db
    .fluent()
    .select()
    .by_id_in(TEST_COLLECTION_NAME)
    .obj()
    .batch(vec!["test-0", "test-5"])
    .await?;
Ok(())
}

What a read by ID costs on each edition is in Query plans and cost.