There are multiple keys on lang in org_openpsa_products_product_i;
mysql> show keys from org_openpsa_products_product_i;
+--------------------------------+------------+----------------------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+--------------------------------+------------+----------------------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| org_openpsa_products_product_i | 0 | PRIMARY | 1 | id | A | 811 | NULL | NULL | | BTREE | |
| org_openpsa_products_product_i | 1 | org_openpsa_products_product_i_sitegroup_idx | 1 | sitegroup | A | 1 | NULL | NULL | | BTREE | |
| org_openpsa_products_product_i | 1 | org_openpsa_products_product_i_sid_idx | 1 | sid | A | 811 | NULL | NULL | | BTREE | |
| org_openpsa_products_product_i | 1 | org_openpsa_products_product_i_sid_idx | 2 | lang | A | 811 | NULL | NULL | | BTREE | |
| org_openpsa_products_product_i | 1 | org_openpsa_products_product_i_lang_idx | 1 | lang | A | 1 | NULL | NULL | | BTREE | |
| org_openpsa_products_product_i | 1 | org_openpsa_products_product_i_title_idx | 1 | title | A | 405 | 200 | NULL | | BTREE | |
| org_openpsa_products_product_i | 1 | sitegroup | 1 | sitegroup | A | 1 | NULL | NULL | | BTREE | |
| org_openpsa_products_product_i | 1 | lang_idx | 1 | lang | A | 1 | NULL | NULL | | BTREE | |
| org_openpsa_products_product_i | 1 | sid_idx | 1 | sid | A | 811 | NULL | NULL | | BTREE | |
+--------------------------------+------------+----------------------------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
9 rows in set (0.00 sec)
