Hello, I'm using MariaDB 13.3.14 I have a very simple test table with an email column and I am using |ANALYZE|to see the behavior of the indexes. If I understand correctly the output of |ANALYZE|, '|rows'|indicates the estimate of records accessed in the table, and |'r_rows'|the actual number of accesses. (Am I correct?) If yes, the issue is that, for a query as simple as: | SELECT*FROMuserWHEREemail ='user@domain.com'| ||| -- user@domain.com exists in email column and it is unique| || If I create a normal index in the |'email'|field, |r_rows=|1. However, if I create a unique index, |r_rows|=|NULL|. If I understand correctly, a NULL value on 'r_rows' means that no access to data has been performed ( https://mariadb.com/kb/en/library/analyze-statement/ ). So my question is, if I have a valid result, how can it be that the table is not accessed? How is the data retrieved when a unique index is used? Here is my output (I remember that the email in the query exists): MariaDB [test2]> create index email on usuario(email); Query OK, 95236 rows affected (0.451 sec) Records: 95236 Duplicates: 0 Warnings: 0 MariaDB [test2]> analyze select * from usuario where email = 'nec.urna.et@volutpatornare.com'; +------+-------------+---------+------+---------------+-------+---------+-------+------+--------+----------+------------+-----------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | r_rows | filtered | r_filtered | Extra | +------+-------------+---------+------+---------------+-------+---------+-------+------+--------+----------+------------+-----------------------+ | 1 | SIMPLE | usuario | ref | email | email | 302 | const | 1 | 1.00 | 100.00 | 100.00 | Using index condition | +------+-------------+---------+------+---------------+-------+---------+-------+------+--------+----------+------------+-----------------------+ 1 row in set (0.001 sec) MariaDB [test2]> drop index email on usuario; Query OK, 95236 rows affected (0.237 sec) Records: 95236 Duplicates: 0 Warnings: 0 MariaDB [test2]> create unique index email on usuario(email); Query OK, 95236 rows affected (0.484 sec) Records: 95236 Duplicates: 0 Warnings: 0 MariaDB [test2]> analyze select * from usuario where email = 'nec.urna.et@volutpatornare.com'; +------+-------------+---------+-------+---------------+-------+---------+-------+------+--------+----------+------------+-------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | r_rows | filtered | r_filtered | Extra | +------+-------------+---------+-------+---------------+-------+---------+-------+------+--------+----------+------------+-------+ | 1 | SIMPLE | usuario | const | email | email | 302 | const | 1 | NULL | 100.00 | NULL | | +------+-------------+---------+-------+---------------+-------+---------+-------+------+--------+----------+------------+-------+ 1 row in set (0.001 sec) Regards. ||