Here is the plan on cvs.openacs.org
QUERY PLAN
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Sort (cost=1179.86..1180.00 rows=55 width=1303)
Sort Key: notification_requests.user_id, notifications.type_id, notifications.notif_date
-> Nested Loop Left Join (cost=26.19..1178.27 rows=55 width=1303)
Filter: ("inner".sent_date IS NULL)
-> Nested Loop (cost=26.19..893.79 rows=55 width=1303)
Join Filter: ("inner".creation_date <= "outer".notif_date)
-> Merge Join (cost=26.19..60.67 rows=165 width=1307)
Merge Cond: (("outer".type_id = "inner".type_id) AND ("outer".object_id = "inner".object_id))
-> Index Scan using notification_requests_type_obj_ on notification_requests (cost=0.00..682.72 rows=14167 width=20)
Filter: (interval_id = 2889)
-> Sort (cost=26.19..26.48 rows=117 width=1299)
Sort Key: notifications.type_id, notifications.object_id
-> Seq Scan on notifications (cost=0.00..22.17 rows=117 width=1299)
-> Index Scan using acs_objects_pk on acs_objects (cost=0.00..5.03 rows=1 width=12)
Index Cond: ("outer".request_id = acs_objects.object_id)
-> Index Scan using notification_user_map_n_u_idx on notification_user_map (cost=0.00..5.16 rows=1 width=16)
Index Cond: (("outer".notification_id = notification_user_map.notification_id) AND ("outer".user_id = notification_user_map.user_id))
