information_schema.statistics.index_type

mysql

type: VARCHAR NOT NULL
5.7-8

mariadb

type: NULL
Note:
Index type, one of BTREE, RTREE, HASH or FULLTEXT. See Storage Engine Index Types.
© 2022 MariaDB
5.1-10.8
type: VARCHAR NOT NULL
Note:
Index type, one of BTREE, RTREE, HASH or FULLTEXT. See Storage Engine Index Types.
© 2022 MariaDB
10.2-10.7

tidb

type: VARCHAR(16) NULL
Note:
The type of the index.
© 2022 PingCAP
4-6.1

postgres

cockroachdb

mssql