transactions.md

Transactions

Transactions let us update multiple documents in a batch. By using transactions, we can make sure that either the documents are all updated or none of them are updated.

let mut session = db.start_session().unwrap();
session.start_transaction(None).unwrap();
// ...
session.commit_transaction().unwrap();

We start a session first and then start a transaction. All operations in //... will be executed at commit_transaction().

Let us see an example.

use polodb_core::Database;

fn main() {
    let db = Database::open_memory().unwrap();
    
    let mut session = db.start_session().unwrap();
    session.start_transaction(None).unwrap();
    
    db.create_collection_with_session("name_of_the_collection", &mut session)
        .unwrap();
    
    let names = db.list_collection_names().unwrap();
    println!("{:?}", names);
    
    let names = db.list_collection_names_with_session(&mut session).unwrap();
    println!("{:?}", names);
    
    session.commit_transaction().unwrap();

    let names = db.list_collection_names().unwrap();
    println!("{:?}", names);
}

Output:

[]
["name_of_the_collection"]
["name_of_the_collection"]

We create a collection in the session. This does not change the database until we execute commit_transaction().

In addition to create_collection_with_session and list_collection_names_with_session, we can also use other methods that end with _with_session, such as insert_many_with_session and update_many_with_session.

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