ALTER TABLE ... DROP VERSIONING

don't add columns to the drop list, INVISIBLE_SYSTEM columns
cannot be recognized as specified by the user

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

@@ -28,6 +28,10 @@ t	CREATE TABLE `t` (
   `a` int(11) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 set system_versioning_alter_history= keep;
+alter table t add system versioning;
+alter table t drop system versioning, drop column row_start;
+ERROR 42000: Can't DROP COLUMN `row_start`; check that it exists
+alter table t drop system versioning;
 alter table t
 add column trx_start bigint(20) unsigned as row start invisible,
 add column trx_end bigint(20) unsigned as row end invisible,

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

@@ -20,6 +20,11 @@ show create table t;
 
 set system_versioning_alter_history= keep;
 
+alter table t add system versioning;
+--error ER_CANT_DROP_FIELD_OR_KEY
+alter table t drop system versioning, drop column row_start;
+alter table t drop system versioning;
+
 --error ER_VERS_FIELD_WRONG_TYPE
 alter table t
   add column trx_start bigint(20) unsigned as row start invisible,

sql/handler.cc

@@ -7135,23 +7135,6 @@ bool Table_scope_and_contents_source_st::vers_fix_system_fields(
   return false;
 }
 
-static bool add_field_to_drop_list_if_not_exists(THD *thd, Alter_info *alter_info, Field *field)
-{
-  DBUG_ASSERT(field);
-  DBUG_ASSERT(field->field_name.str);
-  List_iterator_fast<Alter_drop> it(alter_info->drop_list);
-  while (Alter_drop *drop= it++)
-  {
-    if (!my_strcasecmp(system_charset_info, field->field_name.str, drop->name))
-      return false;
-  }
-
-  alter_info->flags|= Alter_info::ALTER_DROP_COLUMN;
-  Alter_drop *ad= new (thd->mem_root)
-      Alter_drop(Alter_drop::COLUMN, field->field_name.str, false);
-  return !ad || alter_info->drop_list.push_back(ad, thd->mem_root);
-}
-
 static bool is_dropping_primary_key(Alter_info *alter_info)
 {
   List_iterator_fast<Alter_drop> it(alter_info->drop_list);
@@ -7176,8 +7159,7 @@ static bool is_adding_primary_key(Alter_info *alter_info)
 }
 
 bool Vers_parse_info::fix_alter_info(THD *thd, Alter_info *alter_info,
-                                          HA_CREATE_INFO *create_info,
-                                          TABLE *table)
+                                     HA_CREATE_INFO *create_info, TABLE *table)
 {
   TABLE_SHARE *share= table->s;
   const char *table_name= share->table_name.str;
@@ -7206,10 +7188,6 @@ bool Vers_parse_info::fix_alter_info(THD *thd, Alter_info *alter_info,
       return true;
     }
 
-    if (add_field_to_drop_list_if_not_exists(thd, alter_info, share->vers_start_field()) ||
-        add_field_to_drop_list_if_not_exists(thd, alter_info, share->vers_end_field()))
-      return true;
-
     if (share->primary_key != MAX_KEY && !is_adding_primary_key(alter_info) &&
         !is_dropping_primary_key(alter_info))
     {

sql/sql_table.cc

@@ -7950,7 +7950,7 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
           !my_strcasecmp(system_charset_info,field->field_name.str, drop->name))
         break;
     }
-    if (drop && (field->invisible < INVISIBLE_SYSTEM || field->vers_sys_field()))
+    if (drop && field->invisible < INVISIBLE_SYSTEM)
     {
       /* Reset auto_increment value if it was dropped */
       if (MTYP_TYPENR(field->unireg_check) == Field::NEXT_NUMBER &&
@@ -7966,6 +7966,14 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
       bitmap_set_bit(dropped_fields, field->field_index);
       continue;
     }
+    if (!drop && field->invisible == INVISIBLE_SYSTEM &&
+        field->flags & VERS_SYSTEM_FIELD &&
+        alter_info->flags & Alter_info::ALTER_DROP_SYSTEM_VERSIONING)
+    {
+      if (table->s->tmp_table == NO_TMP_TABLE)
+        (void) delete_statistics_for_column(thd, table, field);
+      continue;
+    }
     /* Check if field is changed */
     def_it.rewind();
     while ((def=def_it++))
@@ -7975,7 +7983,7 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
                           &def->change))
 	break;
     }
-    if (def && (field->invisible < INVISIBLE_SYSTEM || field->vers_sys_field()))
+    if (def && field->invisible < INVISIBLE_SYSTEM)
     {						// Field is changed
       def->field=field;
       /*