Question

Somehow I managed to get two indexes named user_id, as shown below. Should I drop, rename and rebuild one of them, or is this no problem?

SHOW INDEXES FROM core_item;

+-----------+------------+-----------+--------------+-----------------+-----------+-------------+----------+--------+------+------------+---------+
| Table     | Non_unique | Key_name  | Seq_in_index | Column_name     | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+-----------+------------+-----------+--------------+-----------------+-----------+-------------+----------+--------+------+------------+---------+
| core_item |          0 | PRIMARY   |            1 | id              | A         |      593642 |     NULL | NULL   |      | BTREE      |         | 
| core_item |          0 | user_id   |            1 | user_id         | A         |       11416 |     NULL | NULL   |      | BTREE      |         | 
| core_item |          0 | user_id   |            2 | product_id      | A         |      593642 |     NULL | NULL   |      | BTREE      |         |
+-----------+------------+-----------+--------------+-----------------+-----------+-------------+----------+--------+------+------------+---------+

Answer 1

It’s a single composite index covering 2 columns.

I think that output of SHOW CREATE TABLE core_item is easier to understand.