MDEV-21941 RENAME doesn't work for system time or period fields

- Ignore system-invisible fields (as well as for setting default value);
- Handle rename of system time and period fields.

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

@@ -174,3 +174,20 @@ alter table t add constraint mytime_1 check (x > 2);
 insert t values (3, @e, @s);
 ERROR 23000: CONSTRAINT `mytime_2` failed for `test`.`t`
 drop table t;
+#
+# MDEV-21941 RENAME doesn't work for system time or period fields
+#
+create or replace table t1 (
+a int, s date, e date,
+period for mytime(s, e));
+alter table t1 rename column s to x;
+alter table t1 rename column e to y;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL,
+  `x` date NOT NULL,
+  `y` date NOT NULL,
+  PERIOD FOR `mytime` (`x`, `y`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;

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

@@ -131,3 +131,17 @@ alter table t add constraint mytime_1 check (x > 2);
 insert t values (3, @e, @s);
 
 drop table t;
+
+--echo #
+--echo # MDEV-21941 RENAME doesn't work for system time or period fields
+--echo #
+create or replace table t1 (
+  a int, s date, e date,
+  period for mytime(s, e));
+
+alter table t1 rename column s to x;
+alter table t1 rename column e to y;
+
+show create table t1;
+# cleanup
+drop table t1;

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

@@ -687,3 +687,26 @@ add column c int without system versioning,
 change column c c int,
 change column b b int without system versioning;
 drop table t;
+#
+# MDEV-21941 RENAME doesn't work for system time or period fields
+#
+create or replace table t1 (a int) with system versioning;
+alter table t1 rename column row_start to x;
+ERROR 42S22: Unknown column 'row_start' in 't1'
+create or replace table t1 (
+a int,
+row_start timestamp(6) as row start invisible,
+row_end timestamp(6) as row end invisible,
+period for system_time (row_start, row_end)
+) with system versioning;
+alter table t1 rename column row_start to x;
+alter table t1 rename column row_end to y;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL,
+  `x` timestamp(6) GENERATED ALWAYS AS ROW START INVISIBLE,
+  `y` timestamp(6) GENERATED ALWAYS AS ROW END INVISIBLE,
+  PERIOD FOR SYSTEM_TIME (`x`, `y`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 WITH SYSTEM VERSIONING
+drop table t1;

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

@@ -581,3 +581,24 @@ alter table t
   change column b b int without system versioning;
 
 drop table t;
+
+--echo #
+--echo # MDEV-21941 RENAME doesn't work for system time or period fields
+--echo #
+create or replace table t1 (a int) with system versioning;
+--error ER_BAD_FIELD_ERROR
+alter table t1 rename column row_start to x;
+
+create or replace table t1 (
+  a int,
+  row_start timestamp(6) as row start invisible,
+  row_end timestamp(6) as row end invisible,
+  period for system_time (row_start, row_end)
+) with system versioning;
+
+alter table t1 rename column row_start to x;
+alter table t1 rename column row_end to y;
+
+show create table t1;
+# cleanup
+drop table t1;

sql/sql_table.cc

@@ -8142,6 +8142,13 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
   Field **f_ptr,*field;
   MY_BITMAP *dropped_fields= NULL; // if it's NULL - no dropped fields
   bool drop_period= false;
+  LEX_CSTRING period_start_name;
+  LEX_CSTRING period_end_name;
+  if (table->s->period.name)
+  {
+    period_start_name= table->s->period_start_field()->field_name;
+    period_end_name= table->s->period_end_field()->field_name;
+  }
   DBUG_ENTER("mysql_prepare_alter_table");
 
   /*
@@ -8338,13 +8345,24 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
                            alter->name.str))
 	  break;
       }
-      if (alter)
+      if (alter && field->invisible < INVISIBLE_SYSTEM)
       {
         if (alter->is_rename())
         {
           def->change= alter->name;
           def->field_name= alter->new_name;
           column_rename_param.fields.push_back(def);
+          if (field->flags & VERS_SYS_START_FLAG)
+            create_info->vers_info.as_row.start= alter->new_name;
+          else if (field->flags & VERS_SYS_END_FLAG)
+            create_info->vers_info.as_row.end= alter->new_name;
+          if (table->s->period.name)
+          {
+            if (field == table->period_start_field())
+              period_start_name= alter->new_name;
+            else if (field == table->period_end_field())
+              period_end_name= alter->new_name;
+          }
         }
         else
         {
@@ -8804,9 +8822,7 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
     }
     else
     {
-      Field *s= table->s->period.start_field(table->s);
+      create_info->period_info.set_period(period_start_name, period_end_name);
-      Field *e= table->s->period.end_field(table->s);
-      create_info->period_info.set_period(s->field_name, e->field_name);
       create_info->period_info.name= table->s->period.name;
     }
   }

sql/table.h

@@ -831,14 +831,28 @@ struct TABLE_SHARE
 
   Field *vers_start_field()
   {
+    DBUG_ASSERT(versioned);
     return field[vers.start_fieldno];
   }
 
   Field *vers_end_field()
   {
+    DBUG_ASSERT(versioned);
     return field[vers.end_fieldno];
   }
 
+  Field *period_start_field() const
+  {
+    DBUG_ASSERT(period.name);
+    return field[period.start_fieldno];
+  }
+
+  Field *period_end_field() const
+  {
+    DBUG_ASSERT(period.name);
+    return field[period.end_fieldno];
+  }
+
   /**
     Cache the checked structure of this table.
 
@@ -1625,6 +1639,19 @@ public:
     return field[s->vers.end_fieldno];
   }
 
+  Field *period_start_field() const
+  {
+    DBUG_ASSERT(s && s->period.name);
+    return field[s->period.start_fieldno];
+  }
+
+  Field *period_end_field() const
+  {
+    DBUG_ASSERT(s && s->period.name);
+    return field[s->period.end_fieldno];
+  }
+
+
   ulonglong vers_start_id() const;
   ulonglong vers_end_id() const;