[MDEV-16888] Add virtual Type_handler::cond_notnull_field_isnull_to_field_eq_zero() - Jira

The code rewriting "datetime_field IS NULL" to "datetime_field='0000-00-00'" has tests for field_type():

class Item_func_isnull :public Item_func_null_predicate

..

  bool arg_is_datetime_notnull_field()

    Item **args= arguments();

    if (args[0]->real_item()->type() == Item::FIELD_ITEM)

      Field *field=((Item_field*) args[0]->real_item())->field;

      if (((field->type() == MYSQL_TYPE_DATE) ||

          (field->type() == MYSQL_TYPE_DATETIME)) &&

          (field->flags & NOT_NULL_FLAG))

        return true;

..

};

COND *

Item_func_isnull::remove_eq_conds(THD *thd, Item::cond_result *cond_value,

                                  bool top_level_arg)

..

   if (((field->type() == MYSQL_TYPE_DATE) ||

        (field->type() == MYSQL_TYPE_DATETIME)) &&

        (field->flags & NOT_NULL_FLAG))

..

This is not friendly to new data types.

We'll remove these tests and add a new method in Type_handler_instead:

  virtual bool cond_notnull_field_isnull_to_field_eq_zero() const

    return false;

and override it for Type_handler_date_common and Type_handler_datetime_common to return true.

blocks

MDEV-4912 Data type plugin API version 1

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