cleanup: remove hidden I_S.VARIABLES and I_S.STATUS tables

their only purpose was to distinguish between
SHOW and SELECT and there are cleaner ways of doing  it.

mysql-test/r/show_check.result

@@ -100,20 +100,20 @@ drop table t1;
 -- after Bug#29394 is implemented.
 show variables like "wait_timeout%";
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def	information_schema	VARIABLES	VARIABLES	VARIABLE_NAME	Variable_name	253	64	12	N	1	0	8
-def	information_schema	VARIABLES	VARIABLES	VARIABLE_VALUE	Value	253	1024	5	Y	0	0	8
+def	information_schema	SESSION_VARIABLES	SESSION_VARIABLES	VARIABLE_NAME	Variable_name	253	64	12	N	1	0	8
+def	information_schema	SESSION_VARIABLES	SESSION_VARIABLES	VARIABLE_VALUE	Value	253	1024	5	Y	0	0	8
 Variable_name	Value
 wait_timeout	28800
 show variables like "WAIT_timeout%";
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def	information_schema	VARIABLES	VARIABLES	VARIABLE_NAME	Variable_name	253	64	12	N	1	0	8
-def	information_schema	VARIABLES	VARIABLES	VARIABLE_VALUE	Value	253	1024	5	Y	0	0	8
+def	information_schema	SESSION_VARIABLES	SESSION_VARIABLES	VARIABLE_NAME	Variable_name	253	64	12	N	1	0	8
+def	information_schema	SESSION_VARIABLES	SESSION_VARIABLES	VARIABLE_VALUE	Value	253	1024	5	Y	0	0	8
 Variable_name	Value
 wait_timeout	28800
 show variables like "this_doesn't_exists%";
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def	information_schema	VARIABLES	VARIABLES	VARIABLE_NAME	Variable_name	253	64	0	N	1	0	8
-def	information_schema	VARIABLES	VARIABLES	VARIABLE_VALUE	Value	253	1024	0	Y	0	0	8
+def	information_schema	SESSION_VARIABLES	SESSION_VARIABLES	VARIABLE_NAME	Variable_name	253	64	0	N	1	0	8
+def	information_schema	SESSION_VARIABLES	SESSION_VARIABLES	VARIABLE_VALUE	Value	253	1024	0	Y	0	0	8
 Variable_name	Value
 show table status from test like "this_doesn't_exists%";
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr

sql/handler.h

@@ -748,7 +748,6 @@ enum enum_schema_tables
   SCH_SESSION_STATUS,
   SCH_SESSION_VARIABLES,
   SCH_STATISTICS,
-  SCH_STATUS,
   SCH_TABLES,
   SCH_TABLESPACES,
   SCH_TABLE_CONSTRAINTS,
@@ -758,7 +757,6 @@ enum enum_schema_tables
   SCH_TRIGGERS,
   SCH_USER_PRIVILEGES,
   SCH_USER_STATS,
-  SCH_VARIABLES,
   SCH_VIEWS
 };
 

sql/sql_parse.cc

@@ -2125,8 +2125,6 @@ int prepare_schema_table(THD *thd, LEX *lex, Table_ident *table_ident,
   case SCH_TABLE_STATS:
   case SCH_INDEX_STATS:
   case SCH_OPEN_TABLES:
-  case SCH_VARIABLES:
-  case SCH_STATUS:
   case SCH_PROCEDURES:
   case SCH_CHARSETS:
   case SCH_ENGINES:

sql/sql_show.cc

@@ -7237,8 +7237,8 @@ int fill_variables(THD *thd, TABLE_LIST *tables, COND *cond)
   enum enum_schema_tables schema_table_idx=
     get_schema_table_idx(tables->schema_table);
   enum enum_var_type option_type= OPT_SESSION;
-  bool upper_case_names= (schema_table_idx != SCH_VARIABLES);
-  bool sorted_vars= (schema_table_idx == SCH_VARIABLES);
+  bool upper_case_names= lex->sql_command != SQLCOM_SHOW_VARIABLES;
+  bool sorted_vars= lex->sql_command == SQLCOM_SHOW_VARIABLES;
 
   if (lex->option_type == OPT_GLOBAL ||
       schema_table_idx == SCH_GLOBAL_VARIABLES)
@@ -7265,9 +7265,9 @@ int fill_status(THD *thd, TABLE_LIST *tables, COND *cond)
   enum enum_schema_tables schema_table_idx=
     get_schema_table_idx(tables->schema_table);
   enum enum_var_type option_type;
-  bool upper_case_names= (schema_table_idx != SCH_STATUS);
+  bool upper_case_names= lex->sql_command != SQLCOM_SHOW_STATUS;
 
-  if (schema_table_idx == SCH_STATUS)
+  if (lex->sql_command == SQLCOM_SHOW_STATUS)
   {
     option_type= lex->option_type;
     if (option_type == OPT_GLOBAL)
@@ -9186,8 +9186,6 @@ ST_SCHEMA_TABLE schema_tables[]=
   {"STATISTICS", stat_fields_info, create_schema_table,
    get_all_tables, make_old_format, get_schema_stat_record, 1, 2, 0,
    OPEN_TABLE_ONLY|OPTIMIZE_I_S_TABLE},
-  {"STATUS", variables_fields_info, create_schema_table, fill_status,
-   make_old_format, 0, 0, -1, 1, 0},
   {"TABLES", tables_fields_info, create_schema_table,
    get_all_tables, make_old_format, get_schema_tables_record, 1, 2, 0,
    OPTIMIZE_I_S_TABLE},
@@ -9209,8 +9207,6 @@ ST_SCHEMA_TABLE schema_tables[]=
    fill_schema_user_privileges, 0, 0, -1, -1, 0, 0},
   {"USER_STATISTICS", user_stats_fields_info, create_schema_table, 
    fill_schema_user_stats, make_old_format, 0, -1, -1, 0, 0},
-  {"VARIABLES", variables_fields_info, create_schema_table, fill_variables,
-   make_old_format, 0, 0, -1, 1, 0},
   {"VIEWS", view_fields_info, create_schema_table,
    get_all_tables, 0, get_schema_views_record, 1, 2, 0,
    OPEN_VIEW_ONLY|OPTIMIZE_I_S_TABLE},

sql/sql_yacc.yy

@@ -12471,7 +12471,7 @@ show_param:
             LEX *lex= Lex;
             lex->sql_command= SQLCOM_SHOW_STATUS;
             lex->option_type= $1;
-            if (prepare_schema_table(thd, lex, 0, SCH_STATUS))
+            if (prepare_schema_table(thd, lex, 0, SCH_SESSION_STATUS))
               MYSQL_YYABORT;
           }
         | opt_full PROCESSLIST_SYM
@@ -12481,7 +12481,7 @@ show_param:
             LEX *lex= Lex;
             lex->sql_command= SQLCOM_SHOW_VARIABLES;
             lex->option_type= $1;
-            if (prepare_schema_table(thd, lex, 0, SCH_VARIABLES))
+            if (prepare_schema_table(thd, lex, 0, SCH_SESSION_VARIABLES))
               MYSQL_YYABORT;
           }
         | charset wild_and_where