Simplified away CONNECT::host

Part of MDEV-19515 - Improve connect speed

sql/handle_connections_win.cc

@@ -376,7 +376,6 @@ struct Pipe_Listener : public Listener
       statistic_increment(connection_errors_internal, &LOCK_status);
       return;
     }
-    connect->host= my_localhost;
     create_new_thread(connect);
   }
 

sql/mysqld.cc

@@ -6293,7 +6293,6 @@ void create_new_thread(CONNECT *connect)
 void handle_accepted_socket(MYSQL_SOCKET new_sock, MYSQL_SOCKET sock)
 {
   CONNECT *connect;
-  bool is_unix_sock;
 
 #ifdef HAVE_LIBWRAP
   {
@@ -6342,8 +6341,8 @@ void handle_accepted_socket(MYSQL_SOCKET new_sock, MYSQL_SOCKET sock)
 
   if ((connect= new CONNECT()))
   {
-    is_unix_sock= (mysql_socket_getfd(sock) ==
-      mysql_socket_getfd(unix_sock));
+    bool is_unix_sock= mysql_socket_getfd(sock) ==
+                       mysql_socket_getfd(unix_sock);
 
     if (!(connect->vio=
       mysql_socket_vio_new(new_sock,
@@ -6365,9 +6364,6 @@ void handle_accepted_socket(MYSQL_SOCKET new_sock, MYSQL_SOCKET sock)
     return;
   }
 
-  if (is_unix_sock)
-    connect->host= my_localhost;
-
   if (mysql_socket_getfd(sock) == mysql_socket_getfd(extra_ip_sock))
   {
     connect->extra_port= 1;

sql/sql_connect.cc

@@ -1517,7 +1517,10 @@ THD *CONNECT::create_thd(THD *thd)
 
   init_net_server_extension(thd);
 
-  thd->security_ctx->host= host;
+  thd->security_ctx->host= thd->net.vio->type == VIO_TYPE_NAMEDPIPE ||
+                           thd->net.vio->type == VIO_TYPE_SOCKET ?
+                           my_localhost : 0;
+
   thd->extra_port=         extra_port;
   thd->scheduler=          scheduler;
   thd->real_id=            real_id;

sql/sql_connect.h

@@ -32,7 +32,6 @@ class CONNECT : public ilink {
 public:
   /* To be copied to THD */
   Vio *vio;                           /* Copied to THD with my_net_init() */
-  const char *host;
   scheduler_functions *scheduler;
   my_thread_id thread_id;
   pthread_t    real_id;
@@ -43,7 +42,7 @@ class CONNECT : public ilink {
   ulonglong    prior_thr_create_utime;
 
   CONNECT()
-    :vio(0), host(0), scheduler(thread_scheduler), thread_id(0), real_id(0),
+    :vio(0), scheduler(thread_scheduler), thread_id(0), real_id(0),
     extra_port(0),
     thread_count_incremented(0), prior_thr_create_utime(0)
   {