Using PostgreSQL from a MoonBit Agent
The MoonBit SDK already includes the generated package for golem:rdbms/postgres@1.5.0.
Add the Package Import
In the component's moon.pkg, add an alias for the package:
import {
"golemcloud/golem_sdk/interface/golem/rdbms/postgres" @pg,
}Open a Connection
let conn = @pg.DbConnection::open("postgres://user:password@localhost:5432/app")
.or_error!("failed to connect to PostgreSQL")Query Data
PostgreSQL placeholders use $1, $2, ...
let result = conn.query(
"SELECT $1::text",
[@pg.DbValue::Text("hello")],
).or_error!("query failed")
let row = result.rows[0]
let value = row.values[0]
let message = match value {
@pg.DbValue::Text(value) => value
@pg.DbValue::Varchar(value) => value
@pg.DbValue::Bpchar(value) => value
_ => abort("unexpected PostgreSQL value")
}Execute Statements
conn.execute(
"INSERT INTO notes (id, body) VALUES ($1, $2)",
[@pg.DbValue::Int4(1), @pg.DbValue::Text("hello")],
).or_error!("insert failed")Transactions
let tx = conn.begin_transaction().or_error!("failed to start transaction")
tx.execute(
"UPDATE notes SET body = $1 WHERE id = $2",
[@pg.DbValue::Text("updated"), @pg.DbValue::Int4(1)],
).or_error!("update failed")
tx.commit().or_error!("commit failed")