debug: don't hide row_start/row_end columns for testing

mysql-test/suite/versioning/r/debug.result

@@ -35,5 +35,20 @@ tt3	CREATE TEMPORARY TABLE `tt3` (
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 disconnect con1;
 connection default;
+set debug_dbug='+d,sysvers_show';
+show create table t3;
+Table	Create Table
+t3	CREATE TABLE `t3` (
+  `a` int(11) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 WITH SYSTEM VERSIONING
+create table t4 (a int);
+show create table t4;
+Table	Create Table
+t4	CREATE TABLE `t4` (
+  `a` int(11) DEFAULT NULL,
+  `row_start` timestamp(6) GENERATED ALWAYS AS ROW START,
+  `row_end` timestamp(6) GENERATED ALWAYS AS ROW END,
+  PERIOD FOR SYSTEM_TIME (`row_start`, `row_end`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 WITH SYSTEM VERSIONING
 set global debug_dbug=@old_dbug;
-drop table t1, t2, t3;
+drop table t1, t2, t3, t4;

mysql-test/suite/versioning/t/debug.test

@@ -25,5 +25,11 @@ show create table tt3;
 --disconnect con1
 --connection default
 
+set debug_dbug='+d,sysvers_show';
+
+show create table t3;
+create table t4 (a int);
+show create table t4;
+
 set global debug_dbug=@old_dbug;
-drop table t1, t2, t3;
+drop table t1, t2, t3, t4;

sql/handler.cc

@@ -6874,7 +6874,7 @@ static Create_field *vers_init_sys_field(THD *thd, const char *field_name, int f
     f->set_handler(&type_handler_timestamp2);
     f->length= MAX_DATETIME_PRECISION;
   }
-  f->invisible= INVISIBLE_SYSTEM;
+  f->invisible= DBUG_EVALUATE_IF("sysvers_show", VISIBLE, INVISIBLE_SYSTEM);
 
   if (f->check(thd))
     return NULL;