Fix: skip compressing if message is a batch one

Author: paper777

src/producer/DefaultMQProducer.cpp

@@ -397,12 +397,13 @@ SendResult DefaultMQProducer::sendKernelImpl(MQMessage& msg,
       if (!isBatchMsg) {
         string unique_id = StringIdMaker::get_mutable_instance().get_unique_id();
         msg.setProperty(MQMessage::PROPERTY_UNIQ_CLIENT_MESSAGE_ID_KEYIDX, unique_id);
+
+        // batch does not support compressing right now,
+        tryToCompressMessage(msg);
       }
 
       LOG_DEBUG("produce before:%s to %s", msg.toString().c_str(), mq.toString().c_str());
 
-      tryToCompressMessage(msg);
-
       SendMessageRequestHeader* requestHeader = new SendMessageRequestHeader();
       requestHeader->producerGroup = getGroupName();
       requestHeader->topic = (msg.getTopic());