MDEV-8372 Use helper methods introduced in MDEV-7824 all around the code

Author: Alexander Barkov

sql/field.cc

@@ -10434,16 +10434,14 @@ Create_field::Create_field(THD *thd, Field *old_field, Field *orig_field)
  if (!default_now) // Give a constant default
  {
  /* Get the value from default_values */
- my_ptrdiff_t diff= orig_field->table->default_values_offset();
- orig_field->move_field_offset(diff);// Points now at default_values
- if (!orig_field->is_real_null())
+ const uchar *dv= orig_field->table->s->default_values;
+ if (!orig_field->is_null_in_record(dv))
  {
  StringBuffer<MAX_FIELD_WIDTH> tmp(charset);
- String *res= orig_field->val_str(&tmp);
+ String *res= orig_field->val_str(&tmp, orig_field->ptr_in_record(dv));
  char *pos= (char*) sql_strmake(res->ptr(), res->length());
  def= new (thd->mem_root) Item_string(thd, pos, res->length(), charset);
  }
- orig_field->move_field_offset(-diff);// Back to record[0]
  }
  }
 }

sql/sql_select.cc

@@ -16571,20 +16571,17 @@ create_tmp_table(THD *thd, TMP_TABLE_PARAM *param, List<Item> &fields,
  inherit the default value that is defined for the field referred
  by the Item_field object from which 'field' has been created.
  */
- my_ptrdiff_t diff;
- Field *orig_field= default_field[i];
+ const Field *orig_field= default_field[i];
  /* Get the value from default_values */
- diff= (my_ptrdiff_t) (orig_field->table->s->default_values-
- orig_field->table->record[0]);
- orig_field->move_field_offset(diff); // Points now at default_values
- if (orig_field->is_real_null())
+ if (orig_field->is_null_in_record(orig_field->table->s->default_values))
  field->set_null();
  else
  {
  field->set_notnull();
- memcpy(field->ptr, orig_field->ptr, field->pack_length());
+ memcpy(field->ptr,
+ orig_field->ptr_in_record(orig_field->table->s->default_values),
+ field->pack_length());
  }
- orig_field->move_field_offset(-diff); // Back to record[0]
  } 
 
  if (from_field[i])