feat: store humans in an actual database

This uses `sqlx` to read/write humans from/to the sample-db.

The schema consists of a custom enum type for episodes, and a table for
humans. For now, the same structs as were used for the GraphQL schema
are being used to (de)serialize database values. This would have been
quite smooth, but sadly, `sqlx`'s derivation can't handle `Vec`s of
custom enums (launchbadge/sqlx#298), so we
have to jump through some hoops by introducing `EpisodeSlice` and
`EpisodeVec` newtypes, which can then implement the required traits
(plus all the required juniper traits, which is the bigger pain).

Since we're using `sqlx`'s macros to check queries at compile time, we
need to connect to the database during compilation. The macro will use
the `DATABASE_URL` environment variable, which it can read from a `.env`
file, so we now write one of these files as part of `make prepare-db`
(note that this is for the benefit of editors, language servers, etc.,
`make run` would already inherit the `DATABASE_URL` when compiling).

Author: Chris Connelly

.gitignore

@@ -1 +1,2 @@
+.env
 /target

Cargo.lock

@@ -8,14 +8,16 @@ edition = "2021"
 [dependencies]
 axum = "0.4.2"
 envy = "0.4.2"
+futures = "0.3.18"
 juniper = "0.15.7"
 juniper_hyper = "0.8.0"
-parking_lot = "0.11.2"
 serde = { version = "1.0.131", features = ["derive"] }
-sqlx = { version = "0.5.9", default-features = false, features = ["macros", "postgres", "runtime-tokio-rustls"] }
+sqlx = { version = "0.5.9", default-features = false, features = ["macros", "postgres", "runtime-tokio-rustls", "uuid"] }
 tokio = { version = "1.14.0", features = ["macros", "rt-multi-thread"] }
 tower = "0.4.11"
 tower-http = { version = "0.2.0", features = ["trace"] }
 tracing = "0.1.29"
 tracing-subscriber = { version = "0.3.3", features = ["env-filter"] }
 uuid = { version = "0.8.2", features = ["v4"] }
+
+[features]

Cargo.toml

@@ -11,6 +11,8 @@ export RUST_LOG ?= rust_graphql_sample=debug,tower_http=debug
 prepare-db: start-db
 	@sqlx database create
 	@sqlx migrate run
+# 	Write a .env file with DATABASE_URL, so that sqlx will always pick it up (e.g. from editor or language server)
+	@echo "DATABASE_URL=$(DATABASE_URL)" > .env
 
 start-db:
 	@scripts/start-db.sh

Makefile

@@ -0,0 +1,10 @@
+CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
+
+CREATE TYPE episode AS ENUM ('new_hope', 'empire', 'jedi');
+
+CREATE TABLE humans (
+	id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+	name TEXT NOT NULL UNIQUE,
+	appears_in episode[] NOT NULL,
+	home_planet TEXT NOT NULL
+);

migrations/20211210224745_create_initial_schema.sql

@@ -1,45 +1,56 @@
-use std::collections::HashMap;
-
-use parking_lot::RwLock;
 use uuid::Uuid;
 
-use super::{Human, NewHuman};
+use crate::model::{Human, NewHuman};
 
 pub(crate) struct Context {
-    _db: sqlx::PgPool,
-    humans: RwLock<HashMap<Uuid, Human>>,
+    db: sqlx::PgPool,
 }
 
 impl Context {
     pub(crate) fn new(db: sqlx::PgPool) -> Self {
-        Self {
-            _db: db,
-            humans: Default::default(),
-        }
+        Self { db }
     }
 
-    pub(crate) fn humans(&self) -> Vec<Human> {
-        self.humans.read().values().cloned().collect()
+    pub(crate) async fn humans(&self) -> Result<Vec<Human>, sqlx::Error> {
+        sqlx::query_as!(
+            Human,
+            "
+SELECT id, name, appears_in AS \"appears_in: _\", home_planet
+FROM humans
+            ",
+        )
+        .fetch_all(&self.db)
+        .await
     }
 
-    pub(crate) fn find_human(&self, id: &Uuid) -> Result<Human, &'static str> {
-        self.humans.read().get(id).cloned().ok_or("not found")
+    pub(crate) async fn find_human(&self, id: &Uuid) -> Result<Human, sqlx::Error> {
+        sqlx::query_as!(
+            Human,
+            "
+SELECT id, name, appears_in AS \"appears_in: _\", home_planet
+FROM humans
+WHERE id = $1
+            ",
+            id
+        )
+        .fetch_one(&self.db)
+        .await
     }
 
-    pub(crate) fn insert_human(&self, new_human: NewHuman) -> Result<Human, &'static str> {
-        let mut humans = self.humans.write();
-
-        if humans
-            .values()
-            .any(|human| human.name() == new_human.name())
-        {
-            return Err("a human with that name already exists");
-        }
-
-        let human = Human::new(new_human);
-        humans.insert(human.id(), human.clone());
-
-        Ok(human)
+    pub(crate) async fn insert_human(&self, new_human: NewHuman) -> Result<Human, sqlx::Error> {
+        sqlx::query_as!(
+            Human,
+            "
+INSERT INTO humans (name, appears_in, home_planet)
+VALUES ($1, $2, $3)
+RETURNING id, name, appears_in AS \"appears_in: _\", home_planet
+            ",
+            new_human.name(),
+            new_human.appears_in() as _,
+            new_human.home_planet(),
+        )
+        .fetch_one(&self.db)
+        .await
     }
 }
 

src/graphql/context.rs

@@ -1,7 +1,6 @@
 mod context;
 mod schema;
 
-use self::schema::{Human, NewHuman};
 pub(crate) use self::{
     context::Context,
     schema::{Mutation, Query},

src/graphql/mod.rs

@@ -1,7 +1,7 @@
 use juniper::FieldResult;
 use uuid::Uuid;
 
-use crate::Context;
+use crate::{Context, model::{NewHuman, Human}};
 
 pub(crate) struct Query;
 
@@ -14,13 +14,13 @@ impl Query {
     }
 
     /// All the humanoid creatures in the Star Wars universe that we know about.
-    fn humans(context: &Context) -> FieldResult<Vec<Human>> {
-        Ok(context.humans())
+    async fn humans(context: &Context) -> FieldResult<Vec<Human>> {
+        Ok(context.humans().await?)
     }
 
     /// A humanoid creature in the Star Wars universe.
-    fn human(context: &Context, id: Uuid) -> FieldResult<Human> {
-        let human = context.find_human(&id)?;
+    async fn human(context: &Context, id: Uuid) -> FieldResult<Human> {
+        let human = context.find_human(&id).await?;
         Ok(human)
     }
 }
@@ -30,77 +30,8 @@ pub(crate) struct Mutation;
 /// The root mutation structure.
 #[juniper::graphql_object(Context = Context)]
 impl Mutation {
-    fn create_human(context: &Context, new_human: NewHuman) -> FieldResult<Human> {
-        let human = context.insert_human(new_human)?;
+    async fn create_human(context: &Context, new_human: NewHuman) -> FieldResult<Human> {
+        let human = context.insert_human(new_human).await?;
         Ok(human)
     }
 }
-
-/// Episodes in the original (and best) Star Wars trilogy.
-#[derive(Clone, Copy, juniper::GraphQLEnum)]
-pub(crate) enum Episode {
-    /// Star Wars: Episode IV – A New Hope
-    NewHope,
-
-    /// Star Wars: Episode V – The Empire Strikes Back
-    Empire,
-
-    /// Star Wars: Episode VI – Return of the Jedi
-    Jedi,
-}
-
-/// A humanoid creature in the Star Wars universe.
-#[derive(Clone, juniper::GraphQLObject)]
-pub(crate) struct Human {
-    /// Their unique identifier, assigned by us.
-    id: Uuid,
-
-    /// Their name.
-    name: String,
-
-    /// The episodes in which they appeared.
-    appears_in: Vec<Episode>,
-
-    /// Their home planet.
-    home_planet: String,
-}
-
-impl Human {
-    pub(crate) fn new(new_human: NewHuman) -> Self {
-        Self {
-            id: Uuid::new_v4(),
-            name: new_human.name,
-            appears_in: new_human.appears_in,
-            home_planet: new_human.home_planet,
-        }
-    }
-
-    pub(crate) fn id(&self) -> Uuid {
-        self.id
-    }
-
-    pub(crate) fn name(&self) -> &str {
-        &self.name
-    }
-}
-
-/// A new humanoid creature in the Star Wars universe.
-///
-/// `id` is assigned by the server upon creation.
-#[derive(juniper::GraphQLInputObject)]
-pub(crate) struct NewHuman {
-    /// Their name.
-    name: String,
-
-    /// The episodes in which they appeared.
-    appears_in: Vec<Episode>,
-
-    /// Their home planet.
-    home_planet: String,
-}
-
-impl NewHuman {
-    pub(crate) fn name(&self) -> &str {
-        &self.name
-    }
-}

src/graphql/schema.rs

@@ -1,4 +1,5 @@
 mod graphql;
+pub(crate) mod model;
 
 use std::{
     net::{Ipv4Addr, SocketAddr, TcpListener},
@@ -17,7 +18,7 @@ use tower_http::trace::TraceLayer;
 use tracing::info;
 use tracing_subscriber::EnvFilter;
 
-use self::graphql::{Context, Mutation, Query};
+pub(crate) use self::graphql::{Context, Mutation, Query};
 
 #[derive(Debug, serde::Deserialize)]
 struct Config {