always emit end when command is complete; release connection to pool on end. Fixes #569

Author: sidorares

lib/commands/command.js

@@ -28,8 +28,10 @@ Command.prototype.execute = function(packet, connection) {
     var err = packet.asError(connection.clientEncoding);
     if (this.onResult) {
       this.onResult(err);
+      this.emit('end');
     } else {
       this.emit('error', err);
+      this.emit('end');
     }
     return true;
   }

lib/connection.js

@@ -714,6 +714,7 @@ Connection.prototype.execute = function execute(sql, values, cb) {
       } else {
         executeCommand.emit('error', err);
       }
+      executeCommand.emit('end');
       return;
     }
 

lib/pool.js

@@ -170,10 +170,9 @@ Pool.prototype.execute = function(sql, values, cb) {
       return cb(err);
     }
 
-    conn.config.namedPlaceholders = useNamedPlaceholders;
-    return conn.execute(sql, values, function() {
+    const executeCmd = conn.execute(sql, values, cb);
+    executeCmd.once('end', function() {
       conn.release();
-      cb.apply(this, arguments);
     });
   });
 };