Disable foreign key checks once per client

This is better. Move from Writer to Client. We can use this in lieu of 
the ping test. Strictly speaking we do not need this set for reading, 
but it's not going to do any harm.

Author: atomicules

adaptor/mysql/client.go

@@ -104,6 +104,11 @@ func (c *Client) Connect() (client.Session, error) {
 			c.db = uri.Path[1:]
 		}
 	}
-	err = c.mysqlSession.Ping()
+	// Replace Ping with an Exec that we need to run for imports anyway
+	// TODO: Remove below rather than just have commented out
+	//err = c.mysqlSession.Ping()
+	// We need to disable Foreign Key Checks for imports
+	// Ideally we don't want to send this _every_ time just once per session
+	_, err = c.mysqlSession.Exec("SET FOREIGN_KEY_CHECKS=0;")
 	return &Session{c.mysqlSession, c.db}, err
 }

adaptor/mysql/writer.go

@@ -43,9 +43,6 @@ func (w *Writer) Write(msg message.Msg) func(client.Session) (message.Msg, error
 			}
 			return msg, nil
 		}
-		// We need to disable Foreign Key Checks for imports
-		// Ideally we don't want to send this _every_ time just once per session
-		s.(*Session).mysqlSession.Exec("SET FOREIGN_KEY_CHECKS=0;")
 		if err := writeFunc(msg, s.(*Session).mysqlSession); err != nil {
 			return nil, err
 		}