Extension:CodeReview/code relations table

mysql> describe code_relations;
+------------+---------+------+-----+---------+-------+
| Field      | Type    | Null | Key | Default | Extra |
+------------+---------+------+-----+---------+-------+
| cf_repo_id | int(11) | NO   | PRI | NULL    |       |
| cf_from    | int(11) | NO   | PRI | NULL    |       |
| cf_to      | int(11) | NO   | PRI | NULL    |       |
+------------+---------+------+-----+---------+-------+