create table ten(a int);

insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);

create table t10 (

  a int not null

) partition by key(a);

insert into t10 select a from ten;

explain partitions select * from t10 where a in (2,3,4);

MariaDB [j2]> explain partitions select * from t10 where a in (2,3,4);

+------+-------------+-------+------------+------+---------------+------+---------+------+------+-------------+

| id   | select_type | table | partitions | type | possible_keys | key  | key_len | ref  | rows | Extra       |

+------+-------------+-------+------------+------+---------------+------+---------+------+------+-------------+

|    1 | SIMPLE      | t10   | p0         | ALL  | NULL          | NULL | NULL    | NULL |   10 | Using where |

+------+-------------+-------+------------+------+---------------+------+---------+------+------+-------------+

MariaDB [j2]> explain format=json select * from t10 where a in (2,3,4)\G

*************************** 1. row ***************************

EXPLAIN: {

  "query_block": {

    "select_id": 1,

    "table": {

      "table_name": "t10",

      "access_type": "ALL",

      "rows": 10,

      "filtered": 100,

      "attached_condition": "(t10.a in (2,3,4))"

    }

  }

}

MySQL [test]> explain format=json select * from t10 where a in (2,3,4)\G

*************************** 1. row ***************************

EXPLAIN: {

  "query_block": {

    "select_id": 1,

    "table": {

      "table_name": "t10",

      "partitions": [

        "p0"

      ],

      "access_type": "ALL",

      "rows": 10,

      "filtered": 100,

      "attached_condition": "(`test`.`t10`.`a` in (2,3,4))"

    }

  }

}