Bug#30079 A check for "hidden" I_S tables is flawed

added check for hidden I_S tables for 'show columns|keys' commands

mysql-test/r/information_schema.result

@@ -1386,3 +1386,7 @@ f7	datetime	NO		NULL
 f8	datetime	YES		2006-01-01 00:00:00	
 drop table t1;
 End of 5.0 tests.
+show fields from information_schema.TABLE_NAMES;
+ERROR 42S02: Unknown table 'TABLE_NAMES' in information_schema
+show keys from information_schema.TABLE_NAMES;
+ERROR 42S02: Unknown table 'TABLE_NAMES' in information_schema

mysql-test/t/information_schema.test

@@ -1089,3 +1089,12 @@ show columns from t1;
 drop table t1;
 
 --echo End of 5.0 tests.
+
+#
+# Bug#30079 A check for "hidden" I_S tables is flawed
+#
+--error 1109
+show fields from information_schema.TABLE_NAMES;
+--error 1109
+show keys from information_schema.TABLE_NAMES;
+

sql/sql_parse.cc

@@ -6427,7 +6427,12 @@ TABLE_LIST *st_select_lex::add_table_to_list(THD *thd,
     ST_SCHEMA_TABLE *schema_table= find_schema_table(thd, ptr->table_name);
     if (!schema_table ||
         (schema_table->hidden && 
-         lex->orig_sql_command == SQLCOM_END))  // not a 'show' command
+         (lex->orig_sql_command == SQLCOM_END ||         // not a 'show' command
+          /*
+            this check is used for show columns|keys from I_S hidden table
+          */
+          lex->orig_sql_command == SQLCOM_SHOW_FIELDS ||
+          lex->orig_sql_command == SQLCOM_SHOW_KEYS)))
     {
       my_error(ER_UNKNOWN_TABLE, MYF(0),
                ptr->table_name, INFORMATION_SCHEMA_NAME.str);