This notifies when a failed request can be retried.
CREATE OR REPLACE RULE file_location_insert_rename_rule AS ON INSERT TO file_location DO NOTIFY rename_data_changed;
CREATE OR REPLACE RULE new_pending_request_rule AS ON INSERT TO pending_request DO NOTIFY new_pending_request;
+CREATE OR REPLACE RULE pending_request_update_rule AS ON UPDATE TO pending_request WHERE new.start IS NULL AND new.failed IS NULL DO SELECT pg_notify('new_pending_request', '');
CREATE OR REPLACE RULE pending_request_ignore_duplicate AS ON INSERT TO pending_request WHERE (EXISTS (SELECT 1 FROM pending_request WHERE (((((pending_request.aid = new.aid) AND (pending_request.eid = new.eid)) AND (pending_request.fid = new.fid)) AND (pending_request.ed2k = new.ed2k)) AND (pending_request.size = new.size)))) DO INSTEAD NOTHING;