Count items in database as much as possible (#344)

* Count items in database as much as possible

* Fix the tests

* Remove two useless queries

* Run pragma directive before each sqlite connection

* Pragma for tests too

* Remove debug messages

plume-models/src/db_conn.rs

@@ -1,4 +1,4 @@
-use diesel::r2d2::{ConnectionManager, Pool, PooledConnection};
+use diesel::{dsl::sql_query, r2d2::{ConnectionManager, CustomizeConnection, Error as ConnError, Pool, PooledConnection}, ConnectionError, RunQueryDsl};
 use rocket::{
     http::Status,
     request::{self, FromRequest},
@@ -38,3 +38,15 @@ impl Deref for DbConn {
         &self.0
     }
 }
+
+// Execute a pragma for every new sqlite connection
+#[derive(Debug)]
+pub struct PragmaForeignKey;
+impl CustomizeConnection<Connection, ConnError> for PragmaForeignKey {
+    #[cfg(feature = "sqlite")] // will default to an empty function for postgres
+    fn on_acquire(&self, conn: &mut Connection) -> Result<(), ConnError> {
+        sql_query("PRAGMA foreign_keys = on;").execute(conn)
+            .map(|_| ())
+            .map_err(|_| ConnError::ConnectionError(ConnectionError::BadConnection(String::from("PRAGMA foreign_keys = on failed"))))
+    }
+}