--{skip-}merge option added which allows the user to disable merge engine and

to avoid the potential security problem.
(see bug #15195: Security Breach with MERGE table)

mysql-test/r/warnings.result

@@ -171,6 +171,13 @@ alter table t1 engine=isam;
 Warnings:
 Warning	1266	Using storage engine MyISAM for table 't1'
 drop table t1;
+create table t1 (id int) engine=merge;
+Warnings:
+Warning	1266	Using storage engine MyISAM for table 't1'
+alter table t1 engine=merge;
+Warnings:
+Warning	1266	Using storage engine MyISAM for table 't1'
+drop table t1;
 create table t1 (id int) type=heap;
 Warnings:
 Warning	1287	'TYPE=storage_engine' is deprecated; use 'ENGINE=storage_engine' instead

mysql-test/t/warnings-master.opt

---skip-isam
+--skip-isam --skip-merge

mysql-test/t/warnings.test

@@ -118,6 +118,10 @@ create table t1 (id int) engine=isam;
 alter table t1 engine=isam;
 drop table t1;
 
+create table t1 (id int) engine=merge;
+alter table t1 engine=merge;
+drop table t1;
+
 #
 # Test for deprecated TYPE= syntax
 #

sql/handler.cc

@@ -73,9 +73,9 @@ struct show_table_type_st sys_table_types[]=
    "Alias for MEMORY", DB_TYPE_HEAP},
   {"MEMORY",	&have_yes,
    "Hash based, stored in memory, useful for temporary tables", DB_TYPE_HEAP},
-  {"MERGE",	&have_yes,
+  {"MERGE",	&have_merge_db,
    "Collection of identical MyISAM tables", DB_TYPE_MRG_MYISAM},
-  {"MRG_MYISAM",&have_yes,
+  {"MRG_MYISAM",&have_merge_db,
    "Alias for MERGE", DB_TYPE_MRG_MYISAM},
   {"ISAM",	&have_isam,
    "Obsolete storage engine, now replaced by MyISAM", DB_TYPE_ISAM},

sql/mysql_priv.h

@@ -1021,7 +1021,7 @@ extern SHOW_COMP_OPTION have_query_cache, have_berkeley_db, have_innodb;
 extern SHOW_COMP_OPTION have_geometry, have_rtree_keys;
 extern SHOW_COMP_OPTION have_crypt;
 extern SHOW_COMP_OPTION have_compress;
-extern SHOW_COMP_OPTION have_blackhole_db;
+extern SHOW_COMP_OPTION have_blackhole_db, have_merge_db;
 
 #ifndef __WIN__
 extern pthread_t signal_thread;

sql/mysqld.cc

@@ -287,6 +287,7 @@ my_bool opt_safe_user_create = 0, opt_no_mix_types = 0;
 my_bool opt_show_slave_auth_info, opt_sql_bin_update = 0;
 my_bool opt_log_slave_updates= 0;
 my_bool	opt_console= 0, opt_bdb, opt_innodb, opt_isam, opt_ndbcluster;
+my_bool opt_merge;
 #ifdef HAVE_NDBCLUSTER_DB
 const char *opt_ndbcluster_connectstring= 0;
 my_bool	opt_ndb_shm, opt_ndb_optimized_node_selection;
@@ -420,7 +421,7 @@ CHARSET_INFO *system_charset_info, *files_charset_info ;
 CHARSET_INFO *national_charset_info, *table_alias_charset;
 
 SHOW_COMP_OPTION have_berkeley_db, have_innodb, have_isam, have_ndbcluster, 
-  have_example_db, have_archive_db, have_csv_db;
+  have_example_db, have_archive_db, have_csv_db, have_merge_db;
 SHOW_COMP_OPTION have_raid, have_openssl, have_symlink, have_query_cache;
 SHOW_COMP_OPTION have_geometry, have_rtree_keys;
 SHOW_COMP_OPTION have_crypt, have_compress;
@@ -4345,7 +4346,8 @@ enum options_mysqld
   OPT_DATETIME_FORMAT,
   OPT_LOG_QUERIES_NOT_USING_INDEXES,
   OPT_DEFAULT_TIME_ZONE,
-  OPT_LOG_SLOW_ADMIN_STATEMENTS
+  OPT_LOG_SLOW_ADMIN_STATEMENTS,
+  OPT_MERGE
 };
 
 
@@ -4705,6 +4707,9 @@ master-ssl",
 #endif /* HAVE_REPLICATION */
   {"memlock", OPT_MEMLOCK, "Lock mysqld in memory.", (gptr*) &locked_in_memory,
    (gptr*) &locked_in_memory, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
+  {"merge", OPT_MERGE, "Enable Merge storage engine. Disable with \
+--skip-merge.",
+   (gptr*) &opt_merge, (gptr*) &opt_merge, 0, GET_BOOL, NO_ARG, 1, 0, 0, 0, 0},
   {"myisam-recover", OPT_MYISAM_RECOVER,
    "Syntax: myisam-recover[=option[,option...]], where option can be DEFAULT, BACKUP, FORCE or QUICK.",
    (gptr*) &myisam_recover_options_str, (gptr*) &myisam_recover_options_str, 0,
@@ -6468,6 +6473,9 @@ get_one_option(int optid, const struct my_option *opt __attribute__((unused)),
       have_berkeley_db= SHOW_OPTION_DISABLED;
 #endif
     break;
+  case OPT_MERGE:
+    have_merge_db= opt_merge ? SHOW_OPTION_YES : SHOW_OPTION_DISABLED;
+    break;
   case OPT_ISAM:
 #ifdef HAVE_ISAM
     if (opt_isam)

sql/set_var.cc

@@ -738,6 +738,7 @@ struct show_var_st init_vars[]= {
   {"have_innodb",	      (char*) &have_innodb,		    SHOW_HAVE},
   {"have_isam",		      (char*) &have_isam,		    SHOW_HAVE},
   {"have_ndbcluster",         (char*) &have_ndbcluster,             SHOW_HAVE},
+  {"have_merge_engine",       (char*) &have_merge_db,               SHOW_HAVE},
   {"have_openssl",	      (char*) &have_openssl,		    SHOW_HAVE},
   {"have_query_cache",        (char*) &have_query_cache,            SHOW_HAVE},
   {"have_raid",		      (char*) &have_raid,		    SHOW_HAVE},