Remove net_printf_error(). Do not talk to network directly in

check_user()/check_connection()/check_for_max_user_connections().

This is a pre-requisite patch for the fix for Bug#12713 "Error in a stored 
function called from a SELECT doesn't cause ROLLBACK of statem"

Implement review comments.


sql/mysql_priv.h:
  check_for_max_user_connections() is used in one place only, make it static.
sql/mysqld.cc:
  Remove net_printf_error(): a consolidation of error reporting facilities
  is necessary to simplify maintenance of the query cache, the 
  client-server protocol, stored procedure continue handlers. 
  Rewrite the only place where its use is somewhat justified 
  (my_error() can not be used since we need to report an error for the thread 
  that does not exist) with my_snprintf()/net_send_error().
sql/protocol.cc:
  Remove net_printf_error().
sql/protocol.h:
  Remove net_printf_error().
sql/sql_connect.cc:
  Remove net_printf_error(). In check_connection()/check_user()/
  check_for_max_user_connections() do not write directly to the network,
  but use the standard my_error() mechanism to record an error in THD.
  It will be sent to the client by the caller. This was the last place
  in the server that would attempt to send an error directly, mainly left 
  untouched by 5.0 refactoring because it is executed only during 
  thread startup.
sql/sql_parse.cc:
  In the old code, when res was greater than 0, it contained an exact 
  error code, e.g. ER_OUT_OF_RESOURCES or NO SUCH DATABASE, 
  or ER_HANDSHAKE_ERROR. I don't know the reason why this error code was 
  ignored, and instead a generic  ER_UNKNOWN_COM_ERROR was pushed into the
  error stack, but knowing the relaxed attitude towards preserving the error
  codes in the old code, I'm inclinded to think that it was a bug.
  
  After this patch, the most specific error message is already pushed,
  so calling my_message() again is useless.
  
  If res is < 0, the error used to be already sent. This is not done
  by the new code, but will be done later, in the end
  of dispatch_command(). When this is done, clear_error() will be called 
  for us - it is in the first lines of do_command.
  
  To sum up, this change is to remove COM_CHANGE_USER specific error handling
  in favor of the standard one employed for all other COM_* commands.

sql/mysql_priv.h

@@ -920,7 +920,6 @@ bool init_new_connection_handler_thread();
 void reset_mqh(LEX_USER *lu, bool get_them);
 bool check_mqh(THD *thd, uint check_command);
 void time_out_user_resource_limits(THD *thd, USER_CONN *uc);
-int check_for_max_user_connections(THD *thd, USER_CONN *uc);
 void decrease_user_connections(USER_CONN *uc);
 void thd_init_client_charset(THD *thd, uint cs_number);
 bool setup_connection_thread_globals(THD *thd);

sql/mysqld.cc

@@ -4302,6 +4302,7 @@ void create_thread_to_handle_connection(THD *thd)
   }
   else
   {
+    char error_message_buff[MYSQL_ERRMSG_SIZE];
     /* Create new thread to handle connection */
     int error;
     thread_created++;
@@ -4320,7 +4321,10 @@ void create_thread_to_handle_connection(THD *thd)
       thd->killed= THD::KILL_CONNECTION;			// Safety
       (void) pthread_mutex_unlock(&LOCK_thread_count);
       statistic_increment(aborted_connects,&LOCK_status);
-      net_printf_error(thd, ER_CANT_CREATE_THREAD, error);
+      /* Can't use my_error() since store_globals has not been called. */
+      my_snprintf(error_message_buff, sizeof(error_message_buff),
+                  ER(ER_CANT_CREATE_THREAD), error);
+      net_send_error(thd, ER_CANT_CREATE_THREAD, error_message_buff);
       (void) pthread_mutex_lock(&LOCK_thread_count);
       close_connection(thd,0,0);
       delete thd;

sql/protocol.cc

@@ -58,7 +58,7 @@ bool Protocol_binary::net_store_data(const uchar *from, size_t length)
 
    Design note:
 
-   net_printf_error and net_send_error are low-level functions
+   net_send_error is a low-level functions
    that shall be used only when a new connection is being
    established or at server startup.
    For SIGNAL/RESIGNAL and GET DIAGNOSTICS functionality it's
@@ -120,124 +120,6 @@ void net_send_error(THD *thd, uint sql_errno, const char *err)
   DBUG_VOID_RETURN;
 }
 
-/*
-   Write error package and flush to client
-   It's a little too low level, but I don't want to use another buffer for
-   this
-
-   Design note:
-
-   net_printf_error and net_send_error are low-level functions
-   that shall be used only when a new connection is being
-   established or at server startup.
-   For SIGNAL/RESIGNAL and GET DIAGNOSTICS functionality it's
-   critical that every error that can be intercepted is issued in one
-   place only, my_message_sql.
-*/
-
-void
-net_printf_error(THD *thd, uint errcode, ...)
-{
-  va_list args;
-  uint length,offset;
-  const char *format;
-#ifndef EMBEDDED_LIBRARY
-  const char *text_pos;
-  int head_length= NET_HEADER_SIZE;
-#else
-  char text_pos[1024];
-#endif
-  NET *net= &thd->net;
-
-  DBUG_ENTER("net_printf_error");
-  DBUG_PRINT("enter",("message: %u",errcode));
-
-  DBUG_ASSERT(!thd->spcont);
-
-  if (net && net->no_send_error)
-  {
-    thd->clear_error();
-    thd->is_fatal_error= 0;			// Error message is given
-    DBUG_PRINT("info", ("sending error messages prohibited"));
-    DBUG_VOID_RETURN;
-  }
-
-  thd->is_slave_error=  1; // needed to catch query errors during replication
-#ifndef EMBEDDED_LIBRARY
-  query_cache_abort(net);	// Safety
-#endif
-  va_start(args,errcode);
-  /*
-    The following is needed to make net_printf_error() work with 0 argument
-    for errorcode and use the argument after that as the format string. This
-    is useful for rare errors that are not worth the hassle to put in
-    errmsg.sys, but at the same time, the message is not fixed text
-  */
-  if (errcode)
-    format= ER(errcode);
-  else
-  {
-    format=va_arg(args,char*);
-    errcode= ER_UNKNOWN_ERROR;
-  }
-  offset= (net->return_errno ?
-	   ((thd->client_capabilities & CLIENT_PROTOCOL_41) ?
-	    2+SQLSTATE_LENGTH+1 : 2) : 0);
-#ifndef EMBEDDED_LIBRARY
-  text_pos=(char*) net->buff + head_length + offset + 1;
-  length= (uint) ((char*)net->buff_end - text_pos);
-#else
-  length=sizeof(text_pos)-1;
-#endif
-  length=my_vsnprintf(my_const_cast(char*) (text_pos),
-                      min(length, sizeof(net->last_error)),
-                      format,args);
-  va_end(args);
-
-  /* Replication slave relies on net->last_* to see if there was error */
-  net->last_errno= errcode;
-  strmake(net->last_error, text_pos, sizeof(net->last_error)-1);
-
-#ifndef EMBEDDED_LIBRARY
-  if (net->vio == 0)
-  {
-    if (thd->bootstrap)
-    {
-      /*
-	In bootstrap it's ok to print on stderr
-	This may also happen when we get an error from a slave thread
-      */
-      fprintf(stderr,"ERROR: %d  %s\n",errcode,text_pos);
-      thd->fatal_error();
-    }
-    DBUG_VOID_RETURN;
-  }
-
-  int3store(net->buff,length+1+offset);
-  net->buff[3]= (net->compress) ? 0 : (uchar) (net->pkt_nr++);
-  net->buff[head_length]=(uchar) 255;		// Error package
-  if (offset)
-  {
-    uchar *pos= net->buff+head_length+1;
-    int2store(pos, errcode);
-    if (thd->client_capabilities & CLIENT_PROTOCOL_41)
-    {
-      pos[2]= '#';      /* To make the protocol backward compatible */
-      memcpy(pos+3, mysql_errno_to_sqlstate(errcode), SQLSTATE_LENGTH);
-    }
-  }
-  VOID(net_real_write(net, net->buff, length+head_length+1+offset));
-#else
-  net->last_errno= errcode;
-  strmake(net->last_error, text_pos, length);
-  strmake(net->sqlstate, mysql_errno_to_sqlstate(errcode), SQLSTATE_LENGTH);
-#endif
-  if (thd->killed != THD::KILL_CONNECTION)
-    push_warning(thd, MYSQL_ERROR::WARN_LEVEL_ERROR, errcode,
-                 text_pos ? text_pos : ER(errcode));
-  thd->is_fatal_error=0;			// Error message is given
-  DBUG_VOID_RETURN;
-}
 
 /*
   Return ok to the client.

sql/protocol.h

@@ -172,7 +172,6 @@ class Protocol_binary :public Protocol
 };
 
 void send_warning(THD *thd, uint sql_errno, const char *err=0);
-void net_printf_error(THD *thd, uint sql_errno, ...);
 void net_send_error(THD *thd, uint sql_errno=0, const char *err=0);
 void send_ok(THD *thd, ha_rows affected_rows=0L, ulonglong id=0L,
 	     const char *info=0);

sql/sql_parse.cc

@@ -915,11 +915,6 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
 
     if (res)
     {
-      /* authentication failure, we shall restore old user */
-      if (res > 0)
-        my_message(ER_UNKNOWN_COM_ERROR, ER(ER_UNKNOWN_COM_ERROR), MYF(0));
-      else
-        thd->clear_error();                     // Error already sent to client
       x_free(thd->security_ctx->user);
       *thd->security_ctx= save_security_ctx;
       thd->user_connect= save_user_connect;