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Introduction

Alchemy makes interacting with SQL databases a breeze. You can use raw SQL, the fully featured query builder or the built in ORM, Rune.

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Connecting to a Database

Out of the box, Alchemy supports connecting to Postgres & MySQL databases. Database is a Service and so is configurable with the config function.

Database.config(default: .postgres(
    host: Env.DB_HOST ?? "localhost",
    database: Env.DB ?? "db",
    username: Env.DB_USER ?? "user",
    password: Env.DB_PASSWORD ?? "password"
))

// Database queries are all asynchronous, using `EventLoopFuture`s in
// their API.
Database.default
    .rawQuery("select * from users;")
    .whenSuccess { rows in
        print("Got \(rows.count) results!")
    }

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Querying data

You can query with raw SQL strings using Database.rawQuery. It supports bindings to protect against SQL injection.

let email = "josh@withapollo.com"

// Executing a raw query
database.rawQuery("select * from users where email='\(email)';")

// Using bindings to protect against SQL injection
database.rawQuery("select * from users where email=?;", values: [.string(email)])

Note regardless of SQL dialect, please use ? as placeholders for bindings. Concrete Databases representing dialects that use other placeholders, such as PostgresDatabase, will replace ?s with the proper placeholder.

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Handling Query Responses

Every query returns a future with an array of SQLRows that you can use to parse out data. You can access all their columns with allColumns or try to get the value of a column with .get(String) throws -> SQLValue.

dataBase.rawQuery("select * from users;")
    .mapEach { (row: SQLRow) in
        print("Got a user with columns: \(row.columns.join(", "))")
        let email = try! row.get("email").string()
        print("The email of this user was: \(email)")
    }

Note that SQLValue contains functions for casting the value to a specific Swift data type, such as .string() above.

let value: SQLValue = ...

let uuid: UUID = try value.uuid()
let string: String = try value.string()
let int: Int = try value.int()
let bool: Bool = try value.bool()
let double: Double = try value.double()
let json: Data = try value.json()

These functions will throw if the value isn’t convertible to that type.

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Transactions

Sometimes, you’ll want to run multiple database queries as a single atomic operation. For this, you can use the transaction() function; a wrapper around SQL transactions. You’ll have exclusive access to a database connection for the lifetime of your transaction.

database.transaction { conn in
    conn.query()
        .where("account" == 1)
        .update(values: ["amount": 100])
        .flatMap { _ in
            conn.query()
                .where("account" == 2)
                .update(values: ["amount": 200])
        }
}