Extension:TitleKey/titlekey table

tk_page
Reference to

tk_namespace
A denormalized copy of the for filtering

tk_key
Normalized title with namespace prefix, case-folded, in space form

Schema
mysql> describe titlekey; +--+--+--+-+-+---+ +--+--+--+-+-+---+ +--+--+--+-+-+---+ 3 rows in set (0.00 sec)
 * Field       | Type             | Null | Key | Default | Extra |
 * tk_page     | int(10) unsigned | NO   | PRI | NULL    |       |
 * tk_namespace | int(11)         | NO   | MUL | NULL    |       |
 * tk_key      | varbinary(255)   | NO   |     | NULL    |       |