Using PostgreSQL from a Rust Agent

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

Imports

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

Open a Connection

let conn = DbConnection::open("postgres://user:password@localhost:5432/app")
    .map_err(|err| format!("{err:?}"))?;

In real apps, prefer a runtime env var or config value for the connection string instead of hardcoding it.

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

PostgreSQL placeholders use $1, $2, ...

let result = conn
    .query(
        "SELECT $1::text",
        vec![DbValue::Text("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::Text(value) | DbValue::Varchar(value) | DbValue::Bpchar(value) => value.clone(),
    other => return Err(format!("unexpected PostgreSQL value: {other:?}")),
};

Execute Statements

let affected = conn
    .execute(
        "INSERT INTO notes (id, body) VALUES ($1, $2)",
        vec![DbValue::Int4(1), DbValue::Text("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 = $1 WHERE id = $2",
    vec![DbValue::Text("updated".to_string()), DbValue::Int4(1)],
)
.map_err(|err| format!("{err:?}"))?;

tx.commit().map_err(|err| format!("{err:?}"))?;

Use rollback() instead of commit() when the operation should be reverted.