Fixed problem of sending ERROR to client after OK or EOF (BUG#6804)

include/mysql_com.h:
  Flag which prevent sending error after EOF or OK sent
mysql-test/r/kill.result:
  test of blocking of sending ERROR after OK or EOF
mysql-test/t/kill.test:
  test of blocking of sending ERROR after OK or EOF
sql/item_func.cc:
  typo fixed
sql/net_serv.cc:
  initialization of flag
sql/protocol.cc:
  check and set of flag no_send_error
sql/sql_parse.cc:
  droping flag no_send_error before new command/query execution

include/mysql_com.h

@@ -187,6 +187,11 @@ typedef struct st_net {
   char save_char;
   my_bool no_send_ok;  /* For SPs and other things that do multiple stmts */
   my_bool no_send_eof; /* For SPs' first version read-only cursors */
+  /*
+    Set if OK packet is already sent, and we do not need to send error
+    messages
+  */
+  my_bool no_send_error;
   /*
     Pointer to query object in query cache, do not equal NULL (0) for
     queries in cache that have not stored its results yet

mysql-test/r/kill.result

@@ -9,3 +9,15 @@ select 4;
 4
 4
 drop table t1;
+select get_lock("a", 10);
+get_lock("a", 10)
+1
+ select get_lock("a", 10);
+get_lock("a", 10)
+NULL
+select 1;
+1
+1
+select RELEASE_LOCK("a");
+RELEASE_LOCK("a")
+1

mysql-test/t/kill.test

@@ -35,3 +35,21 @@ select @id != connection_id();
 connection con2;
 select 4;
 drop table t1;
+
+#
+# test of blocking of sending ERROR after OK or EOF
+#
+connection con1;
+select get_lock("a", 10);
+connection con2;
+let $ID= `select connection_id()`;
+send select get_lock("a", 10);
+connection con1;
+disable_query_log;
+eval kill query $ID;
+enable_query_log;
+connection con2;
+reap;
+select 1;
+connection con1;
+select RELEASE_LOCK("a");

sql/item_func.cc

@@ -3578,7 +3578,7 @@ Item_func_sp::execute(Item **itp)
 #endif
 
   /*
-    We don't need to surpress senfing of ok packet here (by setting
+    We don't need to surpress sending of ok packet here (by setting
     thd->net.no_send_ok to true), because we are not allowing statements
     in functions now.
   */

sql/net_serv.cc

@@ -121,8 +121,7 @@ my_bool my_net_init(NET *net, Vio* vio)
     DBUG_RETURN(1);
   net->buff_end=net->buff+net->max_packet;
   net->vio = vio;
-  net->no_send_ok = 0;
+  net->no_send_ok= net->no_send_eof= net->no_send_error= 0;
-  net->no_send_eof = 0;
   net->error=0; net->return_errno=0; net->return_status=0;
   net->pkt_nr=net->compress_pkt_nr=0;
   net->write_pos=net->read_pos = net->buff;

sql/protocol.cc

@@ -65,6 +65,12 @@ void net_send_error(THD *thd, uint sql_errno, const char *err)
 		      err ? err : net->last_error[0] ?
 		      net->last_error : "NULL"));
 
+  if (net && net->no_send_error)
+  {
+    thd->clear_error();
+    DBUG_PRINT("info", ("sending error messages prohibited"));
+    DBUG_VOID_RETURN;
+  }
   if (thd->spcont && thd->spcont->find_handler(sql_errno,
                                                MYSQL_ERROR::WARN_LEVEL_ERROR))
   {
@@ -154,6 +160,13 @@ net_printf_error(THD *thd, uint errcode, ...)
   DBUG_ENTER("net_printf_error");
   DBUG_PRINT("enter",("message: %u",errcode));
 
+  if (net && net->no_send_error)
+  {
+    thd->clear_error();
+    DBUG_PRINT("info", ("sending error messages prohibited"));
+    DBUG_VOID_RETURN;
+  }
+
   if (thd->spcont && thd->spcont->find_handler(errcode,
                                                MYSQL_ERROR::WARN_LEVEL_ERROR))
   {
@@ -300,6 +313,9 @@ send_ok(THD *thd, ha_rows affected_rows, ulonglong id, const char *message)
   VOID(net_flush(net));
   /* We can't anymore send an error to the client */
   thd->net.report_error= 0;
+  thd->net.no_send_error= 1;
+  DBUG_PRINT("info", ("OK sent, so no more error sendong allowed"));
+
   DBUG_VOID_RETURN;
 }
 
@@ -357,6 +373,8 @@ send_eof(THD *thd, bool no_flush)
       if (!no_flush)
 	VOID(net_flush(net));
     }
+    thd->net.no_send_error= 1;
+    DBUG_PRINT("info", ("EOF sent, so no more error sendong allowed"));
   }
   DBUG_VOID_RETURN;
 }

sql/sql_parse.cc

@@ -960,6 +960,7 @@ void execute_init_command(THD *thd, sys_var_str *init_command_var,
   */
   save_vio= thd->net.vio;
   thd->net.vio= 0;
+  thd->net.no_send_error= 0;
   dispatch_command(COM_QUERY, thd, thd->query, thd->query_length+1);
   rw_unlock(var_mutex);
   thd->client_capabilities= save_client_capabilities;
@@ -1019,6 +1020,7 @@ pthread_handler_decl(handle_one_connection,arg)
     int error;
     NET *net= &thd->net;
     thd->thread_stack= (char*) &thd;
+    net->no_send_error= 0;
 
     if ((error=check_connection(thd)))
     {						// Wrong permissions
@@ -1057,6 +1059,7 @@ pthread_handler_decl(handle_one_connection,arg)
     thd->init_for_queries();
     while (!net->error && net->vio != 0 && !(thd->killed == THD::KILL_CONNECTION))
     {
+      net->no_send_error= 0;
       if (do_command(thd))
 	break;
     }
@@ -2087,6 +2090,7 @@ mysql_execute_command(THD *thd)
   /* most outer SELECT_LEX_UNIT of query */
   SELECT_LEX_UNIT *unit= &lex->unit;
   DBUG_ENTER("mysql_execute_command");
+  thd->net.no_send_error= 0;
 
   /*
     In many cases first table of main SELECT_LEX have special meaning =>