gistfile1.txt

MariaDB [drupal]> select count(ct.id) from contribution_tracking ct left join contribution_source cs on ct.id = cs.contribution_tracking_id where ct.id > 20000000 and cs.contribution_tracking_id is null;
+--------------+
| count(ct.id) |
+--------------+
|        46960 |
+--------------+
1 row in set (8.95 sec)

MariaDB [drupal]> select count(ct.id) from contribution_tracking ct join contribution_source cs on ct.id = cs.contribution_tracking_id where ct.id > 20000000;
+--------------+
| count(ct.id) |
+--------------+
|      6592941 |
+--------------+
1 row in set (12.81 sec)