Reset insert_id on connection sent to pool #1093

Automatically reset mysql->insert_id when a connection is sent to connection pool.
If is not reset to 0 , when a backend connections is assigned to a client, this one can potentially read the last inserted id from the previous client.

lib/MySQL_Session.cpp

@@ -275,6 +275,7 @@ MySQL_Session::MySQL_Session() {
 
 	init(); // we moved this out to allow CHANGE_USER
 
+	last_insert_id=0; // #1093
 }
 
 void MySQL_Session::init() {

lib/MySQL_Thread.cpp

@@ -4215,6 +4215,8 @@ MySQL_Connection * MySQL_Thread::get_MyConn_local(unsigned int _hid) {
 void MySQL_Thread::push_MyConn_local(MySQL_Connection *c) {
 	MySrvC *mysrvc=NULL;
 	mysrvc=(MySrvC *)c->parent;
+	// reset insert_id #1093
+	c->mysql->insert_id = 0;
 	if (mysrvc->status==MYSQL_SERVER_STATUS_ONLINE) {
 		if (c->async_state_machine==ASYNC_IDLE) {
 			cached_connections->add(c);