Add tokio_postgres::GenericClient

We have to make the trait methods differ from the normal methods a bit
by adding Sync + Send bounds to the ToStatement parameter which is a bit
unfortunate, but necessary until GATs async_trait unnecessary.

Closes #357

postgres/src/generic_client.rs

@@ -1,8 +1,7 @@
-use crate::{Statement, ToStatement, Transaction};
-use tokio_postgres::types::ToSql;
-use tokio_postgres::{Error, Row};
+use crate::types::ToSql;
+use crate::{Error, Row, Statement, ToStatement, Transaction};
 
-/// A trait allowing abstraction over connections and transactions
+/// A trait allowing abstraction over connections and transactions.
 pub trait GenericClient {
     /// Like `Client::execute`.
     fn execute<T>(&mut self, query: &T, params: &[&(dyn ToSql + Sync)]) -> Result<u64, Error>

tokio-postgres/Cargo.toml

@@ -35,6 +35,7 @@ with-serde_json-1 = ["postgres-types/with-serde_json-1"]
 with-uuid-0_8 = ["postgres-types/with-uuid-0_8"]
 
 [dependencies]
+async-trait = "0.1"
 bytes = "0.5"
 byteorder = "1.0"
 fallible-iterator = "0.2"

tokio-postgres/src/client.rs

@@ -4,18 +4,17 @@ use crate::connection::{Request, RequestMessages};
 use crate::copy_out::CopyOutStream;
 use crate::query::RowStream;
 use crate::simple_query::SimpleQueryStream;
-use crate::slice_iter;
 #[cfg(feature = "runtime")]
 use crate::tls::MakeTlsConnect;
 use crate::tls::TlsConnect;
-use crate::to_statement::ToStatement;
 use crate::types::{Oid, ToSql, Type};
 #[cfg(feature = "runtime")]
 use crate::Socket;
-use crate::{copy_in, copy_out, query, CancelToken, CopyInSink, Transaction};
-use crate::{prepare, SimpleQueryMessage};
-use crate::{simple_query, Row};
-use crate::{Error, Statement};
+use crate::{
+    copy_in, copy_out, prepare, query, simple_query, slice_iter, CancelToken, CopyInSink, Error,
+    GenericClient, Row, SimpleQueryMessage, Statement, ToStatement, Transaction,
+};
+use async_trait::async_trait;
 use bytes::{Buf, BytesMut};
 use fallible_iterator::FallibleIterator;
 use futures::channel::mpsc;
@@ -495,3 +494,32 @@ impl Client {
         self.inner.sender.is_closed()
     }
 }
+
+#[async_trait]
+impl GenericClient for Client {
+    async fn execute<T>(&mut self, query: &T, params: &[&(dyn ToSql + Sync)]) -> Result<u64, Error>
+    where
+        T: ?Sized + ToStatement + Sync + Send,
+    {
+        self.execute(query, params).await
+    }
+
+    async fn query<T>(
+        &mut self,
+        query: &T,
+        params: &[&(dyn ToSql + Sync)],
+    ) -> Result<Vec<Row>, Error>
+    where
+        T: ?Sized + ToStatement + Sync + Send,
+    {
+        self.query(query, params).await
+    }
+
+    async fn prepare(&mut self, query: &str) -> Result<Statement, Error> {
+        self.prepare(query).await
+    }
+
+    async fn transaction(&mut self) -> Result<Transaction<'_>, Error> {
+        self.transaction().await
+    }
+}

tokio-postgres/src/generic_client.rs

@@ -0,0 +1,27 @@
+use crate::types::ToSql;
+use crate::{Error, Row, Statement, ToStatement, Transaction};
+use async_trait::async_trait;
+
+/// A trait allowing abstraction over connections and transactions.
+#[async_trait]
+pub trait GenericClient {
+    /// Like `Client::execute`.
+    async fn execute<T>(&mut self, query: &T, params: &[&(dyn ToSql + Sync)]) -> Result<u64, Error>
+    where
+        T: ?Sized + ToStatement + Sync + Send;
+
+    /// Like `Client::query`.
+    async fn query<T>(
+        &mut self,
+        query: &T,
+        params: &[&(dyn ToSql + Sync)],
+    ) -> Result<Vec<Row>, Error>
+    where
+        T: ?Sized + ToStatement + Sync + Send;
+
+    /// Like `Client::prepare`.
+    async fn prepare(&mut self, query: &str) -> Result<Statement, Error>;
+
+    /// Like `Client::transaction`.
+    async fn transaction(&mut self) -> Result<Transaction<'_>, Error>;
+}

tokio-postgres/src/lib.rs

@@ -107,6 +107,7 @@ pub use crate::copy_in::CopyInSink;
 pub use crate::copy_out::CopyOutStream;
 use crate::error::DbError;
 pub use crate::error::Error;
+pub use crate::generic_client::GenericClient;
 pub use crate::portal::Portal;
 pub use crate::query::RowStream;
 pub use crate::row::{Row, SimpleQueryRow};
@@ -140,6 +141,7 @@ mod connection;
 mod copy_in;
 mod copy_out;
 pub mod error;
+mod generic_client;
 mod maybe_tls_stream;
 mod portal;
 mod prepare;

tokio-postgres/src/transaction.rs

@@ -12,6 +12,7 @@ use crate::{
     bind, query, slice_iter, CancelToken, Client, CopyInSink, Error, Portal, Row,
     SimpleQueryMessage, Statement, ToStatement,
 };
+use async_trait::async_trait;
 use bytes::Buf;
 use futures::TryStreamExt;
 use postgres_protocol::message::frontend;
@@ -285,3 +286,32 @@ impl<'a> Transaction<'a> {
         })
     }
 }
+
+#[async_trait]
+impl crate::GenericClient for Transaction<'_> {
+    async fn execute<T>(&mut self, query: &T, params: &[&(dyn ToSql + Sync)]) -> Result<u64, Error>
+    where
+        T: ?Sized + ToStatement + Sync + Send,
+    {
+        self.execute(query, params).await
+    }
+
+    async fn query<T>(
+        &mut self,
+        query: &T,
+        params: &[&(dyn ToSql + Sync)],
+    ) -> Result<Vec<Row>, Error>
+    where
+        T: ?Sized + ToStatement + Sync + Send,
+    {
+        self.query(query, params).await
+    }
+
+    async fn prepare(&mut self, query: &str) -> Result<Statement, Error> {
+        self.prepare(query).await
+    }
+
+    async fn transaction<'a>(&'a mut self) -> Result<Transaction<'a>, Error> {
+        self.transaction().await
+    }
+}