Automatically close dead statements

postgres-tokio/src/lib.rs

@@ -16,6 +16,8 @@ use postgres_shared::RowData;
 use std::collections::HashMap;
 use std::fmt;
 use std::io;
+use std::mem;
+use std::sync::mpsc::{self, Sender, Receiver};
 use tokio_core::reactor::Handle;
 
 #[doc(inline)]
@@ -40,6 +42,8 @@ pub struct CancelData {
 
 struct InnerConnection {
     stream: PostgresStream,
+    close_receiver: Receiver<(u8, String)>,
+    close_sender: Sender<(u8, String)>,
     parameters: HashMap<String, String>,
     cancel_data: CancelData,
     next_stmt_id: u32,
@@ -122,8 +126,11 @@ impl Connection {
         stream::connect(params.host(), params.port(), handle)
             .map_err(ConnectError::Io)
             .map(|s| {
+                let (sender, receiver) = mpsc::channel();
                 Connection(InnerConnection {
                     stream: s,
+                    close_sender: sender,
+                    close_receiver: receiver,
                     parameters: HashMap::new(),
                     cancel_data: CancelData {
                         process_id: 0,
@@ -321,6 +328,7 @@ impl Connection {
                     _ => Err(bad_message())
                 }
             })
+            .and_then(|(t, s)| s.close_gc().map(|s| (t, s)))
             .boxed()
     }
 
@@ -336,7 +344,9 @@ impl Connection {
     }
 
     pub fn batch_execute(self, query: &str) -> BoxFuture<Connection, Error> {
-        self.simple_query(query).map(|r| r.1).boxed()
+        self.simple_query(query)
+            .map(|r| r.1)
+            .boxed()
     }
 
     fn raw_prepare(self,
@@ -346,9 +356,9 @@ impl Connection {
         let mut parse = vec![];
         let mut describe = vec![];
         let mut sync = vec![];
+        frontend::sync(&mut sync);
         frontend::parse(name, query, None, &mut parse)
             .and_then(|()| frontend::describe(b'S', name, &mut describe))
-            .and_then(|()| Ok(frontend::sync(&mut sync)))
             .into_future()
             .and_then(move |()| {
                 let it = Some(parse).into_iter()
@@ -457,6 +467,7 @@ impl Connection {
         let mut bind = vec![];
         let mut execute = vec![];
         let mut sync = vec![];
+        frontend::sync(&mut sync);
         let r = frontend::bind(portal,
                                stmt,
                                Some(1),
@@ -482,10 +493,6 @@ impl Connection {
                     .map(|()| s)
                     .map_err(Error::Io)
             })
-            .map(|s| {
-                frontend::sync(&mut sync);
-                s
-            })
             .into_future()
             .and_then(|s| {
                 let it = Some(bind).into_iter()
@@ -546,6 +553,7 @@ impl Connection {
         self.raw_prepare(&name, query)
             .map(|(params, columns, conn)| {
                 let stmt = Statement {
+                    close_sender: conn.0.close_sender.clone(),
                     name: name,
                     params: params,
                     columns: columns,
@@ -555,29 +563,41 @@ impl Connection {
             .boxed()
     }
 
-    fn raw_close(self, type_: u8, name: &str) -> BoxFuture<Connection, Error> {
-        let mut close = vec![];
-        let mut sync = vec![];
-        frontend::close(type_, name, &mut close)
-            .map(|()| frontend::sync(&mut sync))
-            .into_future()
-            .and_then(move |()| {
-                let it = Some(close).into_iter().chain(Some(sync)).map(Ok::<_, io::Error>);
-                self.0.send_all(futures::stream::iter(it))
-            })
-            .and_then(|s| s.0.read())
+    fn close_gc(self) -> BoxFuture<Connection, Error> {
+        let mut messages = vec![];
+        while let Ok((type_, name)) = self.0.close_receiver.try_recv() {
+            let mut buf = vec![];
+            frontend::close(type_, &name, &mut buf).unwrap(); // this can only fail on bad names
+            messages.push(buf);
+        }
+        if messages.is_empty() {
+            return Ok(self).into_future().boxed();
+        }
+
+        let mut buf = vec![];
+        frontend::sync(&mut buf);
+        messages.push(buf);
+        self.0.send_all(futures::stream::iter(messages.into_iter().map(Ok::<_, io::Error>)))
+            .map_err(Error::Io)
+            .and_then(|s| Connection(s.0).finish_close_gc())
+            .boxed()
+    }
+
+    fn finish_close_gc(self) -> BoxFuture<Connection, Error> {
+        self.0.read()
             .map_err(Error::Io)
             .and_then(|(m, s)| {
                 match m {
-                    backend::Message::CloseComplete => Either::A(Ok(Connection(s)).into_future()),
+                    backend::Message::ReadyForQuery(_) => {
+                        Either::A(Ok(Connection(s)).into_future())
+                    }
+                    backend::Message::CloseComplete => Either::B(Connection(s).finish_close_gc()),
                     backend::Message::ErrorResponse(body) => {
                         Either::B(Connection(s).ready_err(body))
                     }
                     _ => Either::A(Err(bad_message()).into_future()),
                 }
             })
-            .and_then(|s| s.ready(()))
-            .map(|((), s)| s)
             .boxed()
     }
 
@@ -601,11 +621,19 @@ struct Column {
 }
 
 pub struct Statement {
+    close_sender: Sender<(u8, String)>,
     name: String,
     params: Vec<Type>,
     columns: Vec<Column>,
 }
 
+impl Drop for Statement {
+    fn drop(&mut self) {
+        let name = mem::replace(&mut self.name, String::new());
+        let _ = self.close_sender.send((b'S', name));
+    }
+}
+
 impl Statement {
     pub fn execute(self,
                    params: &[&ToSql],
@@ -616,10 +644,6 @@ impl Statement {
             .map(|(n, conn)| (n, self, conn))
             .boxed()
     }
-
-    pub fn close(self, conn: Connection) -> BoxFuture<Connection, Error> {
-        conn.raw_close(b'S', &self.name)
-    }
 }
 
 fn connect_err(fields: &mut ErrorFields) -> ConnectError {

postgres-tokio/src/test.rs

@@ -113,11 +113,8 @@ fn prepare_execute() {
             c.unwrap().prepare("CREATE TEMPORARY TABLE foo (id SERIAL PRIMARY KEY, name VARCHAR)")
         })
         .and_then(|(s, c)| s.execute(&[], c))
-        .and_then(|(n, s, c)| {
+        .and_then(|(n, _, c)| {
             assert_eq!(0, n);
-            s.close(c)
-        })
-        .and_then(|c| {
             c.prepare("INSERT INTO foo (name) VALUES ($1), ($2)")
         })
         .and_then(|(s, c)| s.execute(&[&"steven", &"bob"], c))