Asynchronously connecting to a database

[pacman82]

Queries can already be executed asynchronously, but opening the connection is still blocking.

[genusistimelord]

ahh this is nice that your adding this. However can you add a few examples of how to use it?

Currently I am doing something like the below in my async code.

blocking! ( let query = format!(
                r#"SELECT DISTINCT trim(Client) as "Client"
                FROM DMS_Recordkeys
                where {}
                order by client
                OPTION (FORCE ORDER)"#,
                get_type(&dis)
            );

            if let Some(mut cursor) = connection.execute(&query, ()).ok().flatten() {
                let mut buffers = TextRowSet::for_cursor(5000, &mut cursor, Some(4096)).unwrap();
                let mut row_set_cursor = cursor.bind_buffer(&mut buffers).unwrap();

                while let Some(batch) = row_set_cursor.fetch().unwrap_or(None) {
                    for rid in 0..batch.num_rows() {
                        let client = batch.get_string(0, rid);
                        data.push(client);
                    }
                }
            };

            data.sort();
            data
        );

get_string is a custom trait implement which just does

fn get_string(&self, cid: usize, rid: usize) -> String {
        self.at_as_str(cid, rid)
            .unwrap_or(None)
            .unwrap_or_default()
            .to_owned()
            .replace(',', ";")
            .replace('(', "{")
            .replace(')', "}")
    }

any idea on how this could be converter to use the async code or will i need to wait for a few more implementations before I can?

[pacman82]

Most of that you can do already. For asynchronously executing something there is already a code example here: https://docs.rs/odbc-api/latest/odbc_api/struct.Connection.html#method.execute_polling

Of course you don't execute an insert statement, but a query with a result set. You'll find that CursorPolling works much like CursorImpl, but the fetch method is also async.

The Connection you cannot open asynchronously yet. This is what this issue is about. While connecting is not asynchronous, you can of course connect in asynchronous code.

Does this answer your question?

Cheers, Markus

[genusistimelord]

ahh I was having issue trying to figure out how to pass the cursor to TextRowSet::for_cursor(5000, &mut cursor, Some(4096)) so that way i could use the cursor the way I am currently using it.

[pacman82]

Nope, you are right. Oversight on my part. You currently have no (good) way to get metadata on the result set using an asynchronous cursor. I'll open an issue for this.

[genusistimelord]

Thank you. Yeah I was attempting to switch my Axum lib and depreciate my Block method in place of this and noticed there was no way that I could see to use it.

[pacman82]

Yeah, my mistake. Maybe announced it a tad to early 😅