PgConnection: use more obvious/safer query for ping()

sqlx-core/src/postgres/connection/mod.rs

@@ -117,7 +117,8 @@ impl Connection for PgConnection {
     }
 
     fn ping(&mut self) -> BoxFuture<'_, Result<(), Error>> {
-        self.execute("SELECT 1").map_ok(|_| ()).boxed()
+        // By sending a comment we avoid an error if the connection was in the middle of a rowset
+        self.execute("/* SQLx ping */").map_ok(|_| ()).boxed()
     }
 
     #[doc(hidden)]

tests/postgres/postgres.rs

@@ -1,6 +1,6 @@
 use futures::TryStreamExt;
 use sqlx::postgres::PgRow;
-use sqlx::{postgres::Postgres, Executor, Row};
+use sqlx::{postgres::Postgres, Connection, Executor, Row};
 use sqlx_core::postgres::{PgDatabaseError, PgErrorPosition, PgSeverity};
 use sqlx_test::new;
 
@@ -18,6 +18,15 @@ async fn it_connects() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[sqlx_macros::test]
+async fn it_pings() -> anyhow::Result<()> {
+    let mut conn = new::<Postgres>().await?;
+
+    conn.ping().await?;
+
+    Ok(())
+}
+
 #[sqlx_macros::test]
 async fn it_maths() -> anyhow::Result<()> {
     let mut conn = new::<Postgres>().await?;