Index usage for DATE(datetime_column) = const does not work for DELETE and UPDATE

create table t1 (pk int primary key, a datetime, c int, key(a));

INSERT INTO t1 (pk,a,c) VALUES (1,'2009-11-29 13:43:32', 2);

INSERT INTO t1 (pk,a,c) VALUES (2,'2009-11-29 03:23:32', 2);

INSERT INTO t1 (pk,a,c) VALUES (3,'2009-10-16 05:56:32', 2);

INSERT INTO t1 (pk,a,c) VALUES (4,'2010-11-29 13:43:32', 2);

INSERT INTO t1 (pk,a,c) VALUES (5,'2010-10-16 05:56:32', 2);

INSERT INTO t1 (pk,a,c) VALUES (6,'2011-11-29 13:43:32', 2);

INSERT INTO t1 (pk,a,c) VALUES (7,'2012-10-16 05:56:32', 2);

explain format=json  select * from t1 where year(a) = 2010;

explain format=json  update t1 set c = 0 where year(a) = 2010;

explain format=json  delete from t1 where year(a) = 2010;

drop table t1;

explain format=json  select * from t1 where year(a) = 2010;

EXPLAIN

{

  "query_block": {

    "select_id": 1,

    "cost": 0.003808422,

    "nested_loop": [

      {

        "table": {

          "table_name": "t1",

          "access_type": "range",

          "possible_keys": ["a"],

          "key": "a",

          "key_length": "6",

          "used_key_parts": ["a"],

          "loops": 1,

          "rows": 2,

          "cost": 0.003808422,

          "filtered": 100,

          "index_condition": "t1.a between '2010-01-01 00:00:00' and '2010-12-31 23:59:59'"

        }

      }

    ]

  }

}

explain format=json  update t1 set c = 0 where year(a) = 2010;

EXPLAIN

{

  "query_block": {

    "select_id": 1,

    "table": {

      "update": 1,

      "table_name": "t1",

      "access_type": "ALL",

      "rows": 7,

      "attached_condition": "year(t1.a) = 2010"

    }

  }

}

explain format=json  delete from t1 where year(a) = 2010;

EXPLAIN

{

  "query_block": {

    "select_id": 1,

    "table": {

      "delete": 1,

      "table_name": "t1",

      "access_type": "ALL",

      "rows": 7,

      "attached_condition": "year(t1.a) = 2010"

    }

  }

}