Make Pool generic over Backend

examples/contacts/src/main.rs

@@ -1,6 +1,5 @@
 #![feature(async_await)]
 
-use futures::future;
 use failure::Fallible;
 use fake::{
     faker::{
@@ -10,7 +9,8 @@ use fake::{
     },
     Dummy, Fake, Faker,
 };
-use sqlx::pool::Pool;
+use futures::future;
+use sqlx::{pool::Pool, postgres::Postgres};
 
 #[derive(Debug, Dummy)]
 struct Contact {
@@ -40,7 +40,7 @@ async fn main() -> Fallible<()> {
         .user("postgres")
         .database("sqlx__dev__contacts");
 
-    let pool = Pool::new(options);
+    let pool = Pool::<Postgres>::new(options);
 
     {
         let mut conn = pool.acquire().await?;

rust-toolchain

@@ -1 +1 @@
-nightly-2019-08-01
+nightly-2019-08-08

src/backend.rs

@@ -1,6 +1,8 @@
-use crate::row::RawRow;
+use crate::{connection::RawConnection, row::RawRow};
 
 pub trait Backend {
+    type RawConnection: RawConnection;
+
     type RawRow: RawRow;
 
     /// The type used to represent metadata associated with a SQL type.

src/connection.rs

@@ -0,0 +1,9 @@
+use crate::{backend::Backend, ConnectOptions};
+use futures::future::BoxFuture;
+use std::io;
+
+pub trait RawConnection {
+    fn establish(options: ConnectOptions<'_>) -> BoxFuture<io::Result<Self>>
+    where
+        Self: Sized;
+}

src/lib.rs

@@ -35,4 +35,5 @@ pub mod mariadb;
 pub mod postgres;
 
 // TODO: This module is not intended to be directly public
+pub mod connection;
 pub mod pool;

src/pool.rs

@@ -1,7 +1,7 @@
-use crate::{postgres::Connection as C, ConnectOptions};
+use super::connection::RawConnection;
+use crate::{backend::Backend, ConnectOptions};
 use crossbeam_queue::{ArrayQueue, SegQueue};
-use futures::TryFutureExt;
-use futures::channel::oneshot;
+use futures::{channel::oneshot, TryFutureExt};
 use std::{
     io,
     ops::{Deref, DerefMut},
@@ -15,33 +15,51 @@ use std::{
 // TODO: Reap old connections
 // TODO: Clean up (a lot) and document what's going on
 // TODO: sqlx::ConnectOptions needs to be removed and replaced with URIs everywhere
-// TODO: Make Pool generic over Backend (requires a generic sqlx::Connection type)
 
-#[derive(Clone)]
-pub struct Pool {
-    inner: Arc<InnerPool>,
+pub struct Pool<B>
+where
+    B: Backend,
+{
+    inner: Arc<InnerPool<B>>,
 }
 
-struct InnerPool {
+impl<B> Clone for Pool<B>
+where
+    B: Backend,
+{
+    fn clone(&self) -> Self {
+        Self {
+            inner: Arc::clone(&self.inner),
+        }
+    }
+}
+
+struct InnerPool<B>
+where
+    B: Backend,
+{
     options: ConnectOptions<'static>,
-    idle: ArrayQueue<Idle>,
-    waiters: SegQueue<oneshot::Sender<Live>>,
+    idle: ArrayQueue<Idle<B>>,
+    waiters: SegQueue<oneshot::Sender<Live<B>>>,
     total: AtomicUsize,
 }
 
-impl Pool {
-    pub fn new<'a>(options: ConnectOptions<'a>) -> Pool {
-        Pool {
+impl<B> Pool<B>
+where
+    B: Backend,
+{
+    pub fn new<'a>(options: ConnectOptions<'a>) -> Self {
+        Self {
             inner: Arc::new(InnerPool {
                 options: options.into_owned(),
                 idle: ArrayQueue::new(10),
                 total: AtomicUsize::new(0),
-                waiters: SegQueue::new()
+                waiters: SegQueue::new(),
             }),
         }
     }
 
-    pub async fn acquire(&self) -> io::Result<Connection> {
+    pub async fn acquire(&self) -> io::Result<Connection<B>> {
         self.inner
             .acquire()
             .map_ok(|live| Connection::new(live, &self.inner))
@@ -49,8 +67,11 @@ impl Pool {
     }
 }
 
-impl InnerPool {
-    async fn acquire(&self) -> io::Result<Live> {
+impl<B> InnerPool<B>
+where
+    B: Backend,
+{
+    async fn acquire(&self) -> io::Result<Live<B>> {
         if let Ok(idle) = self.idle.pop() {
             log::debug!("acquire: found idle connection");
 
@@ -79,7 +100,7 @@ impl InnerPool {
         self.total.store(total + 1, Ordering::SeqCst);
         log::debug!("acquire: no idle connections; establish new connection");
 
-        let connection = C::establish(self.options.clone()).await?;
+        let connection = B::RawConnection::establish(self.options.clone()).await?;
         let live = Live {
             connection,
             since: Instant::now(),
@@ -88,7 +109,7 @@ impl InnerPool {
         Ok(live)
     }
 
-    fn release(&self, mut connection: Live) {
+    fn release(&self, mut connection: Live<B>) {
         while let Ok(waiter) = self.waiters.pop() {
             connection = match waiter.send(connection) {
                 Ok(()) => {
@@ -107,13 +128,20 @@ impl InnerPool {
 }
 
 // TODO: Need a better name here than [pool::Connection] ?
-pub struct Connection {
-    connection: Option<Live>,
-    pool: Arc<InnerPool>,
+
+pub struct Connection<B>
+where
+    B: Backend,
+{
+    connection: Option<Live<B>>,
+    pool: Arc<InnerPool<B>>,
 }
 
-impl Connection {
-    fn new(connection: Live, pool: &Arc<InnerPool>) -> Self {
+impl<B> Connection<B>
+where
+    B: Backend,
+{
+    fn new(connection: Live<B>, pool: &Arc<InnerPool<B>>) -> Self {
         Self {
             connection: Some(connection),
             pool: Arc::clone(pool),
@@ -121,8 +149,11 @@ impl Connection {
     }
 }
 
-impl Deref for Connection {
-    type Target = C;
+impl<B> Deref for Connection<B>
+where
+    B: Backend,
+{
+    type Target = B::RawConnection;
 
     #[inline]
     fn deref(&self) -> &Self::Target {
@@ -131,7 +162,10 @@ impl Deref for Connection {
     }
 }
 
-impl DerefMut for Connection {
+impl<B> DerefMut for Connection<B>
+where
+    B: Backend,
+{
     #[inline]
     fn deref_mut(&mut self) -> &mut Self::Target {
         // PANIC: Will not panic unless accessed after drop
@@ -139,7 +173,10 @@ impl DerefMut for Connection {
     }
 }
 
-impl Drop for Connection {
+impl<B> Drop for Connection<B>
+where
+    B: Backend,
+{
     fn drop(&mut self) {
         log::debug!("release: dropping connection; store back in queue");
         if let Some(connection) = self.connection.take() {
@@ -148,12 +185,18 @@ impl Drop for Connection {
     }
 }
 
-struct Idle {
-    connection: Live,
+struct Idle<B>
+where
+    B: Backend,
+{
+    connection: Live<B>,
     since: Instant,
 }
 
-struct Live {
-    connection: C,
+struct Live<B>
+where
+    B: Backend,
+{
+    connection: B::RawConnection,
     since: Instant,
 }

src/postgres/connection/establish.rs

@@ -1,4 +1,4 @@
-use super::Connection;
+use super::RawConnection;
 use crate::{
     postgres::protocol::{Authentication, Message, PasswordMessage, StartupMessage},
     ConnectOptions,
@@ -6,7 +6,7 @@ use crate::{
 use std::{borrow::Cow, io};
 
 pub async fn establish<'a, 'b: 'a>(
-    conn: &'a mut Connection,
+    conn: &'a mut RawConnection,
     options: ConnectOptions<'b>,
 ) -> io::Result<()> {
     let user = &*options.user.expect("user is required");

src/postgres/connection/mod.rs

@@ -2,6 +2,7 @@ use super::protocol::{Encode, Message, Terminate};
 use crate::ConnectOptions;
 use bytes::{BufMut, BytesMut};
 use futures::{
+    future::BoxFuture,
     io::{AsyncReadExt, AsyncWrite, AsyncWriteExt},
     ready,
     task::{Context, Poll},
@@ -16,7 +17,7 @@ mod get;
 mod prepare;
 mod select;
 
-pub struct Connection {
+pub struct RawConnection {
     stream: TcpStream,
 
     // Do we think that there is data in the read buffer to be decoded
@@ -39,7 +40,7 @@ pub struct Connection {
     secret_key: u32,
 }
 
-impl Connection {
+impl RawConnection {
     pub async fn establish(options: ConnectOptions<'_>) -> io::Result<Self> {
         let stream = TcpStream::connect((&*options.host, options.port)).await?;
         let mut conn = Self {
@@ -135,3 +136,10 @@ impl Connection {
         Ok(())
     }
 }
+
+impl crate::connection::RawConnection for RawConnection {
+    #[inline]
+    fn establish(options: ConnectOptions<'_>) -> BoxFuture<io::Result<Self>> {
+        Box::pin(RawConnection::establish(options))
+    }
+}

src/postgres/connection/prepare.rs

@@ -1,4 +1,4 @@
-use super::Connection;
+use super::RawConnection;
 use crate::{
     postgres::{
         protocol::{self, BindValues},
@@ -10,12 +10,12 @@ use crate::{
 
 pub struct Prepare<'a, 'b> {
     query: &'b str,
-    pub(super) connection: &'a mut Connection,
+    pub(super) connection: &'a mut RawConnection,
     pub(super) bind: BindValues,
 }
 
 #[inline]
-pub fn prepare<'a, 'b>(connection: &'a mut Connection, query: &'b str) -> Prepare<'a, 'b> {
+pub fn prepare<'a, 'b>(connection: &'a mut RawConnection, query: &'b str) -> Prepare<'a, 'b> {
     // TODO: Use a hash map to cache the parse
     // TODO: Use named statements
     Prepare {
@@ -41,7 +41,7 @@ impl<'a, 'b> Prepare<'a, 'b> {
         self
     }
 
-    pub(super) fn finish(self) -> &'a mut Connection {
+    pub(super) fn finish(self) -> &'a mut RawConnection {
         self.connection.write(protocol::Parse {
             portal: "",
             query: self.query,

src/postgres/mod.rs

@@ -2,7 +2,7 @@ use crate::backend::Backend;
 
 mod connection;
 
-pub use connection::Connection;
+pub use connection::RawConnection;
 
 mod protocol;
 
@@ -11,6 +11,7 @@ pub mod types;
 pub struct Postgres;
 
 impl Backend for Postgres {
+    type RawConnection = RawConnection;
     type RawRow = protocol::DataRow;
     type TypeMetadata = types::TypeMetadata;
 }

src/row.rs

@@ -45,6 +45,7 @@ where
     }
 }
 
+#[allow(unused)]
 macro_rules! impl_from_row_tuple {
     ($B:ident: $( ($idx:tt) -> $T:ident, $ST:ident );+;) => {
         impl<$($ST,)+ $($T,)+> crate::row::FromRow<$B, ($($ST,)+)> for ($($T,)+)
@@ -60,6 +61,7 @@ macro_rules! impl_from_row_tuple {
     };
 }
 
+#[allow(unused)]
 macro_rules! impl_from_row_tuples_for_backend {
     ($B:ident) => {
         impl_from_row_tuple!($B: