Reduce frequent alloc of Query_Processor_Output

A new Query_Processor_Output (qpo) is allocated for every query.
Allocation is now done once per session, thus speeding up execution time
under memory profiler

include/query_processor.h

@@ -125,6 +125,12 @@ class Query_Processor_Output {
 		l_free(sizeof(Query_Processor_Output),ptr);
 	}
 	Query_Processor_Output() {
+		init();
+	}
+	~Query_Processor_Output() {
+		destroy();
+	}
+	void init() {
 		ptr=NULL;
 		size=0;
 		destination_hostgroup=-1;
@@ -139,9 +145,10 @@ class Query_Processor_Output {
 		new_query=NULL;
 		error_msg=NULL;
 	}
-	~Query_Processor_Output() {
+	void destroy() {
 		if (error_msg) {
 			free(error_msg);
+			error_msg=NULL;
 		}
 	}
 };

lib/MySQL_Session.cpp

@@ -192,7 +192,7 @@ void MySQL_Session::operator delete(void *ptr) {
 MySQL_Session::MySQL_Session() {
 	thread_session_id=0;
 	pause_until=0;
-	qpo=NULL;
+	qpo=new Query_Processor_Output();
 //	Session_STMT_Manager=NULL;
 	start_time=0;
 	command_counters=new StatCounters(15,10,false);
@@ -255,6 +255,8 @@ MySQL_Session::~MySQL_Session() {
 	if (admin==false && connections_handler==false && mirror==false) {
 		__sync_fetch_and_sub(&MyHGM->status.client_connections,1);
 	}
+	assert(qpo);
+	delete qpo;
 //	if (Session_STMT_Manager) {
 //		delete Session_STMT_Manager;
 //	}
@@ -2826,10 +2828,11 @@ void MySQL_Session::RequestEnd(MySQL_Data_Stream *myds) {
 	}
 
 	// clean qpo
-	if (qpo) {
-		GloQPro->delete_QP_out(qpo);
-		qpo=NULL;
-	}
+	//if (qpo) {
+	//	GloQPro->delete_QP_out(qpo);
+	//	qpo=NULL;
+	//}
+	GloQPro->delete_QP_out(qpo);
 	// if there is an associated myds, clean its status
 	if (myds) {
 		// if there is a mysql connection, clean its status

lib/Query_Processor.cpp

@@ -602,8 +602,11 @@ SQLite3_result * Query_Processor::get_query_digests_reset() {
 
 
 Query_Processor_Output * Query_Processor::process_mysql_query(MySQL_Session *sess, void *ptr, unsigned int size, Query_Info *qi) {
-	Query_Processor_Output *ret=NULL;
-	ret=new Query_Processor_Output();
+	// to avoid unnecssary deallocation/allocation, we initialize qpo witout new allocation
+	//Query_Processor_Output *ret=NULL;
+	//ret=new Query_Processor_Output();
+	Query_Processor_Output *ret=sess->qpo;
+	ret->init();
 	SQP_par_t *qp=NULL;
 	if (qi) {
 		qp=(SQP_par_t *)&qi->QueryParserArgs;
@@ -829,7 +832,8 @@ __exit_process_mysql_query:
 void Query_Processor::delete_QP_out(Query_Processor_Output *o) {
 	//l_free(sizeof(QP_out_t),o);
 	if (o) {
-		delete o;
+		//delete o; // do not deallocate, but "destroy" it
+		o->destroy();
 	}
 };