Blackbird

A SQLite database wrapper and model layer, using Swift concurrency and Codable, with no other dependencies.

Philosophy:

Prioritize speed of development over all else.
No code generation.
No schema definitions.
Automatic migrations.
Async by default.
Use Swift’s type system and key-paths instead of strings whenever possible.

Project status

Blackbird is a beta.

Minor changes may still occur that break backwards compatibility with code or databases.

I'm using Blackbird in shipping software now, but do so at your own risk.

BlackbirdModel

A protocol to store structs in the SQLite-powered Blackbird.Database, with compiler-checked key-paths for common operations.

Here's how you define a table:

import Blackbird

struct Post: BlackbirdModel {
    @BlackbirdColumn var id: Int
    @BlackbirdColumn var title: String
    @BlackbirdColumn var url: URL?
}

That's it. No CREATE TABLE, no separate table-definition logic, no additional steps.

And automatic migrations. Want to add or remove columns or indexes, or start using more of Blackbird's features such as custom enum columns, unique indexes, or custom primary keys? Just change the code:

struct Post: BlackbirdModel {
    static var primaryKey: [BlackbirdColumnKeyPath] = [ \.$guid, \.$id ]

    static var indexes: [[BlackbirdColumnKeyPath]] = [
        [ \.$title ],
        [ \.$publishedDate, \.$format ],
    ]

    static var uniqueIndexes: [[BlackbirdColumnKeyPath]] = [
        [ \.$guid ],
    ]
    
    enum Format: Int, BlackbirdIntegerEnum {
        case markdown
        case html
    }
    
    @BlackbirdColumn var id: Int
    @BlackbirdColumn var guid: String
    @BlackbirdColumn var title: String
    @BlackbirdColumn var publishedDate: Date?
    @BlackbirdColumn var format: Format
    @BlackbirdColumn var url: URL?
    @BlackbirdColumn var image: Data?
}

…and Blackbird will automatically migrate the table to the new schema at runtime.

Queries

Write instances safely and easily to a Blackbird.Database:

let post = Post(id: 1, title: "What I had for breakfast")
try await post.write(to: db)

Perform queries in many different ways, preferring structured queries using key-paths for compile-time checking, type safety, and convenience:

// Fetch by primary key
let post = try await Post.read(from: db, id: 2)

// Or with a WHERE condition, using compiler-checked key-paths:
let posts = try await Post.read(from: db, matching: \.$title == "Sports")

// Select custom columns, with row dictionaries typed by key-path:
for row in try await Post.query(in: db, columns: [\.$id, \.$image], matching: \.$url != nil) {
    let postID = row[\.$id]       // returns Int
    let imageData = row[\.$image] // returns Data?
}

SQL is never required, but it's always available:

try await Post.query(in: db, "UPDATE $T SET format = ? WHERE date < ?", .html, date)

let posts = try await Post.read(from: db, sqlWhere: "title LIKE ? ORDER BY RANDOM()", "Sports%")

for row in try await Post.query(in: db, "SELECT MAX(id) AS max FROM $T WHERE url = ?", url) {
    let maxID = row["max"]?.intValue
}

Monitor for row- and column-level changes with Combine:

let listener = Post.changePublisher(in: db).sink { change in
    if change.hasPrimaryKeyChanged(7) {
        print("Post 7 has changed")
    }

    if change.hasColumnChanged(\.$title) {
        print("A title has changed")
    }
}

// Or monitor a single column by key-path:
let listener = Post.changePublisher(in: db, columns: [\.$title]).sink { _ in
    print("A post's title changed")
}

// Or listen for changes for a specific primary key:
let listener = Post.changePublisher(in: db, primaryKey: 3, columns: [\.$title]).sink { _ in
    print("Post 3's title changed")
}

SwiftUI

Blackbird is designed for SwiftUI, offering async-loading, automatically-updating result wrappers:

struct RootView: View {
    // The database that all child views will automatically use
    @StateObject var database = try! Blackbird.Database.inMemoryDatabase()

    var body: some View {
        PostListView()
        .environment(\.blackbirdDatabase, database)
    }
}

struct PostListView: View {
    // Async-loading, auto-updating array of matching instances
    @BlackbirdLiveModels({ try await Post.read(from: $0, orderBy: .ascending(\.$id)) }) var posts
    
    // Async-loading, auto-updating rows from a custom query
    @BlackbirdLiveQuery(tableName: "Post", { try await $0.query("SELECT MAX(id) AS max FROM Post") }) var maxID

    var body: some View {
        VStack {
            if posts.didLoad {
                List {
                    ForEach(posts.results) { post in
                        NavigationLink(destination: PostView(post: post.liveModel)) {
                            Text(post.title)
                        }
                    }
                }
            } else {
                ProgressView()
            }
        }
        .navigationTitle(maxID.didLoad ? "\(maxID.results.first?["max"]?.intValue ?? 0) posts" : "Loading…")
    }
}

struct PostView: View {
    // Auto-updating instance
    @BlackbirdLiveModel var post: Post?

    var body: some View {
        VStack {
            if let post {
                Text(post.title)
            }
        }
    }
}

Blackbird.Database

A lightweight async wrapper around SQLite that can be used with or without BlackbirdModel.

let db = try Blackbird.Database(path: "/tmp/db.sqlite")

// SELECT with parameterized queries
for row in try await db.query("SELECT id FROM posts WHERE state = ?", 1) {
    let id = row["id"]?.intValue
    // ...
}

// Run direct queries
try await db.execute("UPDATE posts SET comments = NULL")

// Transactions with synchronous queries
try await db.transaction { core in
    try core.query("INSERT INTO posts VALUES (?, ?)", 16, "Sports!")
    try core.query("INSERT INTO posts VALUES (?, ?)", 17, "Dewey Defeats Truman")
}

Wishlist for future Swift-language capabilities

Static type reflection for cleaner schema detection: Swift currently has no way to reflect a type's properties without creating an instance — Mirror only reflects property names and values of given instances. If the language adds static type reflection in the future, my schema detection wouldn't need to rely on a hack using a Decoder to generate empty instances.
KeyPath to/from String, static reflection of a type's KeyPaths: With the abilities to get a type's available KeyPaths (without some awful hacks) and create KeyPaths from strings at runtime, many of my hacks using Codable could be replaced with KeyPaths, which would be cleaner and probably much faster.
Method to get CodingKeys enum names and custom values: It's currently impossible to get the names of CodingKeys cases without resorting to this awful hack. Decoders must know these names to perform proper decoding to arbitrary types that may have custom CodingKeys declared. If this hack ever stops working, BlackbirdModel cannot support custom CodingKeys.
Cleaner protocol name (Blackbird.Model): Protocols can't contain dots or be nested within another type.
Nested struct definitions inside protocols could make a lot of my "BlackbirdModel…" names shorter.

FAQ

why is it called blackbird

The plane, of course.

It's old, awesome, and ridiculously fast. Well, this database library is based on old, awesome tech (SQLite), and it's ridiculously fast.

(If I'm honest, though, it's mostly because it's a cool-ass plane. I don't even really care about planes, generally. Just that one.)

you know there are lots of other things called that

Of course there are. Who cares?

This is a database engine that'll be used by, at most, a handful of nerds. It doesn't matter what it's called.

I like unique names (rather than generic or descriptive names, like Model or SwiftSQLite) because they're easier to search for and harder to confuse with other types. So I wanted something memorable. I suppose I could've called it something like ButtDB — memorable! — but as I use it over the coming years, I wanted to type something cooler after all of my struct definitions.

why don't you support [SQLite feature]

Blackbird is designed to make it very fast and easy to write apps that have the most common, straightforward database needs.

Custom SQL is supported in many ways, but more advanced SQLite behavior like triggers, views, windows, foreign-key constraints, cascading writes, partial or expression indexes, virtual columns, etc. are not directly supported by Blackbird and may cause undefined behavior if used.

By not supporting esoteric or specialized features that apps typically don't need, Blackbird is able to offer a cleaner API and more useful functionality for common cases.

why didn't you just use [other SQLite library]

I like to write my own libraries.

My libraries can perfectly match my needs and the way I expect them to work. And if my needs or expectations change, I can change the libraries.

I also learn a great deal when writing them, exercising and improving my skills to benefit the rest of my work.

And when I write the libraries, I understand how everything works as I'm using them, therefore creating fewer bugs and writing more efficient software.

you know [other SQLite library] is faster

I know. Ironic, considering that I named this one after the fastest plane.

Blackbird is optimized for speed of development. It's pretty fast in execution, too, but clarity, ease of use, reduced repetition, and simple tooling are higher priorities.

Blackbird also offers automatic caching and fine-grained change reporting. This helps apps avoid many unnecessary queries, reloads, and UI refreshes, which can result in faster overall app performance.

Other Swift SQLite libraries can be faster at raw database performance by omitting much of Blackbird's reflection, abstraction, and key-path usage. Some use code-generation methods, which can execute very efficiently but complicate development more than I'd like. Others take less-abstracted approaches that enable more custom behavior but make usage more complicated.

I've chosen different trade-offs to better fit my needs. I've never written an app that was too slow to read its database, but I've frequently struggled with maintenance of large, complex codebases.

Blackbird's goal is to achieve my ideal balance of ease-of-use and bug-avoidance, even though it's therefore not the fastest SQLite library in execution.

Phones keep getting faster, but a bug is a bug forever.

marcoarment/Blackbird