MDEV-4875 Can't restore a mysqldump if --add-drop-database meets general_log

or slow query log when the log_output=TABLE.

When this happens, we temporary disable by changing log_output until
we've created the general_log and slow_log tables again.

Move </database> in xml mode until after the transaction_registry.

General_log and slow_log tables where moved to be first to be dumped so
that the disabling of the general/slow queries is minimal.

client/mysqldump.c

@@ -5229,6 +5229,55 @@ int init_dumping_views(char *qdatabase __attribute__((unused)))
 } /* init_dumping_views */
 
 
+/*
+mysql specific database initialization.
+
+SYNOPSIS
+  init_dumping_mysql_tables
+
+  protections around dumping general/slow query log
+  qdatabase      quoted name of the "mysql" database
+
+RETURN VALUES
+  0        Success.
+  1        Failure.
+*/
+static int init_dumping_mysql_tables(char *qdatabase)
+{
+  DBUG_ENTER("init_dumping_mysql_tables");
+
+  if (opt_drop_database)
+    fprintf(md_result_file,
+            "\n/*!50106 SET @save_log_output=@@LOG_OUTPUT*/;\n"
+            "/*M!100203 EXECUTE IMMEDIATE IF(@@LOG_OUTPUT='TABLE' AND (@@SLOW_QUERY_LOG=1 OR @@GENERAL_LOG=1),"
+              "\"SET GLOBAL LOG_OUTPUT='NONE'\", \"DO 0\") */;\n");
+
+  DBUG_RETURN(init_dumping_tables(qdatabase));
+}
+
+
+static void dump_first_mysql_tables(char *database)
+{
+  char table_type[NAME_LEN];
+  char ignore_flag;
+  DBUG_ENTER("dump_first_mysql_tables");
+
+  if (!get_table_structure((char *) "general_log",
+                           database, table_type, &ignore_flag) )
+    verbose_msg("-- Warning: get_table_structure() failed with some internal "
+                "error for 'general_log' table\n");
+  if (!get_table_structure((char *) "slow_log",
+                           database, table_type, &ignore_flag) )
+    verbose_msg("-- Warning: get_table_structure() failed with some internal "
+                "error for 'slow_log' table\n");
+  /* general and slow query logs exist now */
+  if (opt_drop_database)
+    fprintf(md_result_file,
+            "\n/*!50106 SET GLOBAL LOG_OUTPUT=@save_log_output*/;\n\n");
+  DBUG_VOID_RETURN;
+}
+
+
 /*
 Table Specific database initialization.
 
@@ -5335,7 +5384,6 @@ static int dump_all_tables_in_db(char *database)
   char table_buff[NAME_LEN*2+3];
   char hash_key[2*NAME_LEN+2];  /* "db.tablename" */
   char *afterdot;
-  my_bool general_log_table_exists= 0, slow_log_table_exists=0;
   my_bool transaction_registry_table_exists= 0;
   int using_mysql_db= !my_strcasecmp(charset_info, database, "mysql");
   DBUG_ENTER("dump_all_tables_in_db");
@@ -5343,11 +5391,15 @@ static int dump_all_tables_in_db(char *database)
   afterdot= strmov(hash_key, database);
   *afterdot++= '.';
 
-  if (init_dumping(database, init_dumping_tables))
+  if (init_dumping(database, using_mysql_db ? init_dumping_mysql_tables
+                   : init_dumping_tables))
     DBUG_RETURN(1);
   if (opt_xml)
     print_xml_tag(md_result_file, "", "\n", "database", "name=", database, NullS);
 
+  if (using_mysql_db)
+    dump_first_mysql_tables(database);
+
   if (lock_tables)
   {
     DYNAMIC_STRING query;
@@ -5436,24 +5488,16 @@ static int dump_all_tables_in_db(char *database)
     else
     {
       /*
-        If general_log and slow_log exists in the 'mysql' database,
+        If transaction_registry exists in the 'mysql' database,
          we should dump the table structure. But we cannot
          call get_table_structure() here as 'LOCK TABLES' query got executed
          above on the session and that 'LOCK TABLES' query does not contain
-         'general_log' and 'slow_log' tables. (you cannot acquire lock
-         on log tables). Hence mark the existence of these log tables here and
+         'transaction_registry'. Hence mark the existence of the table here and
          after 'UNLOCK TABLES' query is executed on the session, get the table
          structure from server and dump it in the file.
       */
-      if (using_mysql_db)
-      {
-        if (!my_strcasecmp(charset_info, table, "general_log"))
-          general_log_table_exists= 1;
-        else if (!my_strcasecmp(charset_info, table, "slow_log"))
-          slow_log_table_exists= 1;
-        else if (!my_strcasecmp(charset_info, table, "transaction_registry"))
-          transaction_registry_table_exists= 1;
-      }
+      if (using_mysql_db && !my_strcasecmp(charset_info, table, "transaction_registry"))
+        transaction_registry_table_exists= 1;
     }
   }
 
@@ -5474,39 +5518,25 @@ static int dump_all_tables_in_db(char *database)
     DBUG_PRINT("info", ("Dumping routines for database %s", database));
     dump_routines_for_db(database);
   }
-  if (opt_xml)
-  {
-    fputs("</database>\n", md_result_file);
-    check_io(md_result_file);
-  }
   if (lock_tables)
     (void) mysql_query_with_error_report(mysql, 0, "UNLOCK TABLES");
   if (using_mysql_db)
   {
-    char table_type[NAME_LEN];
-    char ignore_flag;
-    if (general_log_table_exists)
-    {
-      if (!get_table_structure((char *) "general_log",
-                               database, table_type, &ignore_flag) )
-        verbose_msg("-- Warning: get_table_structure() failed with some internal "
-                    "error for 'general_log' table\n");
-    }
-    if (slow_log_table_exists)
-    {
-      if (!get_table_structure((char *) "slow_log",
-                               database, table_type, &ignore_flag) )
-        verbose_msg("-- Warning: get_table_structure() failed with some internal "
-                    "error for 'slow_log' table\n");
-    }
     if (transaction_registry_table_exists)
     {
+       char table_type[NAME_LEN];
+       char ignore_flag;
       if (!get_table_structure((char *) "transaction_registry",
                                database, table_type, &ignore_flag) )
         verbose_msg("-- Warning: get_table_structure() failed with some internal "
                     "error for 'transaction_registry' table\n");
     }
   }
+  if (opt_xml)
+  {
+    fputs("</database>\n", md_result_file);
+    check_io(md_result_file);
+  }
   if (flush_privileges && using_mysql_db)
   {
     fprintf(md_result_file,"\n--\n-- Flush Grant Tables \n--\n");

mysql-test/main/mysqldump.test

@@ -2916,4 +2916,64 @@ DROP DATABASE test2;
 SET sql_mode=@save_sql_mode;
 --remove_file $MYSQLTEST_VARDIR/tmp/dumptest1.sql
 
+--echo #
+--echo # MDEV-4875 Can't restore a mysqldump if --add-drop-database meets general_log
+--echo #
+
+CREATE DATABASE test1;
+--echo # Dump mysql database
+--exec $MYSQL_DUMP --add-drop-database --databases mysql test1 > $MYSQLTEST_VARDIR/tmp/dumptest1.sql
+
+--disable_warnings
+DROP VIEW IF EXISTS mysql.user;
+DROP TABLE IF EXISTS mysql.global_priv;
+DROP TABLE IF EXISTS mysql.user;
+--enable_warnings
+#DROP TABLE IF EXISTS mysql.transaction_registry;
+#DROP TABLE IF EXISTS mysql.slow_log;
+#DROP TABLE IF EXISTS mysql.general_log;
+DROP TABLE IF EXISTS mysql.time_zone_transition_type;
+DROP TABLE IF EXISTS mysql.time_zone_transition;
+DROP TABLE IF EXISTS mysql.time_zone_name;
+DROP TABLE IF EXISTS mysql.time_zone_leap_second;
+DROP TABLE IF EXISTS mysql.time_zone;
+DROP TABLE IF EXISTS mysql.tables_priv;
+DROP TABLE IF EXISTS mysql.table_stats;
+DROP TABLE IF EXISTS mysql.servers;
+DROP TABLE IF EXISTS mysql.roles_mapping;
+DROP TABLE IF EXISTS mysql.proxies_priv;
+DROP TABLE IF EXISTS mysql.procs_priv;
+DROP TABLE IF EXISTS mysql.proc;
+DROP TABLE IF EXISTS mysql.plugin;
+DROP TABLE IF EXISTS mysql.innodb_table_stats;
+DROP TABLE IF EXISTS mysql.innodb_index_stats;
+DROP TABLE IF EXISTS mysql.index_stats;
+DROP TABLE IF EXISTS mysql.host;
+DROP TABLE IF EXISTS mysql.help_topic;
+DROP TABLE IF EXISTS mysql.help_relation;
+DROP TABLE IF EXISTS mysql.help_keyword;
+DROP TABLE IF EXISTS mysql.help_category;
+DROP TABLE IF EXISTS mysql.gtid_slave_pos;
+DROP TABLE IF EXISTS mysql.func;
+DROP TABLE IF EXISTS mysql.event;
+DROP TABLE IF EXISTS mysql.db;
+DROP TABLE IF EXISTS mysql.columns_priv;
+DROP TABLE IF EXISTS mysql.column_stats;
+
+--echo # Abbreviated contents
+--replace_regex /Create_time="[0-9]{4}-[0-9]{2}-[0-9]{2} [0-9]{2}:[0-9]{2}:[0-9]{2}"/Create_time="TIMESTAMP"/
+--exec $MYSQL_DUMP --xml --skip-comments --no-data --add-drop-database --databases mysql test1
+
+SET @save_general_log=@@GENERAL_LOG;
+SET GLOBAL LOG_OUTPUT='TABLE', GLOBAL GENERAL_LOG=1;
+
+--echo # Restore mysql database while general log is active
+--exec $MYSQL < $MYSQLTEST_VARDIR/tmp/dumptest1.sql
+--echo # No failure at this stage is the object of the test
+SELECT @@GLOBAL.LOG_OUTPUT, @@GLOBAL.GENERAL_LOG;
+SET GLOBAL LOG_OUTPUT=DEFAULT, GLOBAL GENERAL_LOG=@save_general_log;
+TRUNCATE TABLE mysql.general_log;
+DROP DATABASE test1;
+--remove_file $MYSQLTEST_VARDIR/tmp/dumptest1.sql
+
 --echo # End of 10.3 tests