Dodatni indeks na tabeli master nije potreban jer mysql automatski pravi relaciju one-to-many izmedju tabela categories i master, jer je polje category_id u tabeli categories primarni kljuc. Dakle problem ne lezi u tome...
Kôd:
mysql> explain select * from categories,master where categories.category_id=master.category_id;
+----+-------------+------------+--------+---------------+---------+---------+-------------------------+-------+-------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+------------+--------+---------------+---------+---------+-------------------------+-------+-------+
| 1 | SIMPLE | master | ALL | NULL | NULL | NULL | NULL | 40000 | |
| 1 | SIMPLE | categories | eq_ref | PRIMARY | PRIMARY | 4 | test.master.category_id | 1 | |
+----+-------------+------------+--------+---------------+---------+---------+-------------------------+-------+-------+
2 rows in set (0.00 sec)
Dodatni indeksi ne mogu da poprave performanse upita, jer se i tako i tako citaju svi zapisi iz tabele master.
Mrzelo me da kreiram jos koju tabelu i da vidim sta se onda desava...
