Why is rust-mongodb so slow? [duplicate] - mongodb

Question

This question already has an answer here:
Why is my Rust program slower than the equivalent Java program?
(1 answer)
Closed last month.
I've written the following simple code to test the performance difference between Rust and Python.
Here's the Rust version:
#![allow(unused)]
use mongodb::{sync::Client, options::ClientOptions, bson::doc, bson::Document};
fn cursor_iterate()-> mongodb::error::Result<()>{
// setup
let mongo_url = "mongodb://localhost:27017";
let db_name = "MYDB";
let collection_name = "MYCOLLECTION";
let client = Client::with_uri_str(mongo_url)?;
let database = client.database(db_name);
let collection = database.collection::<Document>(collection_name);
// println!("{:?}", collection.count_documents(None, None));
let mut cursor = collection.find(None, None)?;
let mut count = 0;
for result in cursor {
count += 1;
}
println!("Doc count: {}", count);
Ok(())
}
fn main() {
cursor_iterate();
}
This simple cursor iterator takes around 8 seconds with time cargo run:
Finished dev [unoptimized + debuginfo] target(s) in 0.05s
Running `target/debug/bbson`
Doc count: 14469
real 0m8.545s
user 0m8.471s
sys 0m0.067s
Here's the equivalent Python code:
import pymongo
def main():
url = "mongodb://localhost:27017"
db = "MYDB"
client = pymongo.MongoClient(url)
coll = client.get_database(db).get_collection("MYCOLLECTION")
count = 0
for doc in coll.find({}):
count += 1
print('Doc count: ', count)
if __name__ == "__main__":
main()
It takes about a second to run with time python3 test.py:
Doc count: 14469
real 0m1.079s
user 0m0.603s
sys 0m0.116s
So what makes the Rust code this slow? Is it the sync? the equivalent C++ code takes about 100ms.
EDIT: After running in the --release mode, I get:
Doc count: 14469
real 0m0.928s
user 0m0.871s
sys 0m0.041s
still barely matching the python version.

Answer 1

The answer is already in your output:
Finished dev [unoptimized + debuginfo] target(s) in 0.05s
Running `target/debug/bbson`
Doc count: 14469
real 0m8.545s
user 0m8.471s
sys 0m0.067s
It says unoptimized.
Use cargo run --release to enable optimizations.
Further, don't use time cargo run, because that also times the time it takes to compile your program.
Instead, use:
cargo build --release
time target/release/bbson