Add indexing to tables

There are some strategic indexes that are not working, making the tables very slow with large joins. This works very well in combination with the previous patch I sent that changes the LEFT JOIN's into INNER JOINS.

Here is the EXPLAINS without and then with the patch:

WITHOUT

mysql> EXPLAIN
    -> SELECT s.sid, s.submitted, s.remote_addr, sd.cid, sd.no, sd.data
    -> FROM webform_submissions as s
    -> LEFT JOIN webform_submitted_data as sd on (sd.sid = s.sid)
    -> WHERE sd.nid = 8012;
+----+-------------+-------+------+---------------+---------+---------+----------------------+-------+-------------+
| id | select_type | table | type | possible_keys | key     | key_len | ref                  | rows  | Extra       |
+----+-------------+-------+------+---------------+---------+---------+----------------------+-------+-------------+
|  1 | SIMPLE      | s     | ALL  | NULL          | NULL    | NULL    | NULL                 | 31667 |             |
|  1 | SIMPLE      | sd    | ref  | PRIMARY       | PRIMARY | 8       | const,stevedev.s.sid |  2952 | Using where |
+----+-------------+-------+------+---------------+---------+---------+----------------------+-------+-------------+

WITH

mysql> EXPLAIN    
    -> SELECT s.sid, s.submitted, s.remote_addr, sd.cid, sd.no, sd.data
    -> FROM webform_submissions as s
    -> LEFT JOIN webform_submitted_data as sd on (sd.sid = s.sid)
    -> WHERE sd.nid = 8012;
+----+-------------+-------+------+---------------+------+---------+-----------------+--------+-------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref             | rows   | Extra       |
+----+-------------+-------+------+---------------+------+---------+-----------------+--------+-------------+
|  1 | SIMPLE      | sd    | ALL  | PRIMARY,sid   | NULL | NULL    | NULL            | 332068 | Using where |
|  1 | SIMPLE      | s     | ref  | sid           | sid  | 4       | stevedev.sd.sid |      1 |             |
+----+-------------+-------+------+---------------+------+---------+-----------------+--------+-------------+

steve