Using MySQL from a Rust Agent

golem-rust already exposes the host bindings for golem:rdbms/mysql@1.5.0, so you do not need an extra crate.

Imports

use golem_rust::bindings::golem::rdbms::mysql::{
    DbConnection,
    DbValue,
};

Open a Connection

let conn = DbConnection::open("mysql://user:password@localhost:3306/app")
    .map_err(|err| format!("{err:?}"))?;

If the user asks for a method that returns a plain String, keep the public method signature as String and handle host errors inside the method with expect(...) or panic!(...) rather than changing the signature to Result<String, _>.

Query Data

MySQL placeholders use ?.

let result = conn
    .query(
        "SELECT ?",
        vec![DbValue::Varchar("hello".to_string())],
    )
    .map_err(|err| format!("{err:?}"))?;
 
let row = result.rows.first().ok_or("query returned no rows")?;
let value = row.values.first().ok_or("query returned no columns")?;
 
let message = match value {
    DbValue::Varchar(value)
    | DbValue::Text(value)
    | DbValue::Tinytext(value)
    | DbValue::Mediumtext(value)
    | DbValue::Longtext(value)
    | DbValue::Fixchar(value) => value.clone(),
    other => return Err(format!("unexpected MySQL value: {other:?}")),
};

Execute Statements

let affected = conn
    .execute(
        "INSERT INTO notes (id, body) VALUES (?, ?)",
        vec![DbValue::Int(1), DbValue::Varchar("hello".to_string())],
    )
    .map_err(|err| format!("{err:?}"))?;

Transactions

let tx = conn.begin_transaction().map_err(|err| format!("{err:?}"))?;
 
tx.execute(
    "UPDATE notes SET body = ? WHERE id = ?",
    vec![DbValue::Varchar("updated".to_string()), DbValue::Int(1)],
)
.map_err(|err| format!("{err:?}"))?;
 
tx.commit().map_err(|err| format!("{err:?}"))?;

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