Extension:Proofread Page/pr index table

mysql> describe pr_index; ++-+--+-+-+---+ ++-+--+-+-+---+ ++-+--+-+-+---+
 * Field     | Type    | Null | Key | Default | Extra |
 * pr_page_id | int(11) | NO  | PRI | NULL    |       |
 * pr_count  | int(11) | NO   |     | 0       |       |
 * pr_q0     | int(11) | NO   |     | 0       |       |
 * pr_q1     | int(11) | NO   |     | 0       |       |
 * pr_q2     | int(11) | NO   |     | 0       |       |
 * pr_q3     | int(11) | NO   |     | 0       |       |
 * pr_q4     | int(11) | NO   |     | 0       |       |