Dropped FULLTEXT helper index remains in mysql.innodb_index_stats

DROP DATABASE IF EXISTS test_ftsstats;

CREATE DATABASE test_ftsstats;

USE test_ftsstats;

CREATE TABLE t (

  id INT NOT NULL,

  v VARCHAR(32) NOT NULL,

  PRIMARY KEY (id)

) ENGINE=InnoDB;

CREATE FULLTEXT INDEX ft ON t (v);

DROP INDEX ft ON t;

TRUNCATE TABLE t;

-- These two lists should be the same index names for t.

-- STATISTICS / SHOW INDEX: PRIMARY only.

-- innodb_index_stats still has FTS_DOC_ID_INDEX (the dropped FULLTEXT helper).

SHOW INDEX FROM t;

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

| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Ignored |

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

| t     |          0 | PRIMARY  |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               | NO      |

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

SELECT DISTINCT INDEX_NAME

FROM information_schema.STATISTICS

WHERE TABLE_SCHEMA = 'test_ftsstats' AND TABLE_NAME = 't';

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

| INDEX_NAME |

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

| PRIMARY    |

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

SELECT DISTINCT index_name

FROM mysql.innodb_index_stats

WHERE database_name = 'test_ftsstats' AND table_name = 't';

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

| index_name       |

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

| FTS_DOC_ID_INDEX |

| PRIMARY          |

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