--- /dev/null
+BEGIN;
+
+-- SELECT evergreen.upgrade_deps_block_check('1XXX', :eg_version);
+
+ALTER TABLE action_trigger.event_definition
+ ADD COLUMN retention_interval INTERVAL;
+
+CREATE OR REPLACE FUNCTION action_trigger.check_valid_retention_interval()
+ RETURNS TRIGGER AS $_$
+BEGIN
+
+ /*
+ * 1. Retention intervals are alwyas allowed on active hooks.
+ * 2. On passive hooks, retention intervals are only allowed
+ * when the event definition has a max_delay value and the
+ * retention_interval value is greater than the difference
+ * beteween the delay and max_delay values.
+ */
+ PERFORM TRUE FROM action_trigger.hook
+ WHERE key = NEW.hook AND NOT passive;
+
+ IF FOUND THEN
+ RETURN NEW;
+ END IF;
+
+ IF NEW.max_delay IS NOT NULL THEN
+ IF EXTRACT(EPOCH FROM NEW.retention_interval) >
+ ABS(EXTRACT(EPOCH FROM (NEW.max_delay - NEW.delay))) THEN
+ RETURN NEW; -- all good
+ ELSE
+ RAISE EXCEPTION 'retention_interval is too short';
+ END IF;
+ ELSE
+ RAISE EXCEPTION 'retention_interval requires max_delay';
+ END IF;
+END;
+$_$ LANGUAGE PLPGSQL;
+
+CREATE CONSTRAINT TRIGGER is_valid_retention_interval
+ AFTER INSERT OR UPDATE ON action_trigger.event_definition
+ FOR EACH ROW WHEN (NEW.retention_interval IS NOT NULL)
+ EXECUTE PROCEDURE action_trigger.check_valid_retention_interval();
+
+CREATE OR REPLACE FUNCTION action_trigger.purge_events() RETURNS VOID AS $_$
+/**
+ * Deleting expired events without simultaneously deleting their outputs
+ * creates orphaned outputs. Deleting their outputs and all of the events
+ * linking back to them, plus any outputs those events link to is messy and
+ * inefficient. It's simpler to handle them in 2 sweeping steps.
+ *
+ * 1. Delete expired events.
+ * 2. Delete orphaned event outputs.
+ *
+ * This has the added benefit of removing outputs that may have been
+ * orphaned by some other process. Such outputs are not usuable by
+ * the system.
+ *
+ * This does not guarantee that all events within an event group are
+ * purged at the same time. In such cases, the remaining events will
+ * be purged with the next instance of the purge (or soon thereafter).
+ * This is another nod toward efficiency over completeness of old
+ * data that's circling the bit bucket anyway.
+ */
+BEGIN
+
+ DELETE FROM action_trigger.event WHERE id IN (
+ SELECT evt.id
+ FROM action_trigger.event evt
+ JOIN action_trigger.event_definition def ON (def.id = evt.event_def)
+ WHERE def.retention_interval IS NOT NULL
+ AND evt.state <> 'pending'
+ AND evt.update_time < (NOW() - def.retention_interval)
+ );
+
+ WITH linked_outputs AS (
+ SELECT templates.id AS id FROM (
+ SELECT DISTINCT(template_output) AS id
+ FROM action_trigger.event WHERE template_output IS NOT NULL
+ UNION
+ SELECT DISTINCT(error_output) AS id
+ FROM action_trigger.event WHERE error_output IS NOT NULL
+ UNION
+ SELECT DISTINCT(async_output) AS id
+ FROM action_trigger.event WHERE async_output IS NOT NULL
+ ) templates
+ ) DELETE FROM action_trigger.event_output
+ WHERE id NOT IN (SELECT id FROM linked_outputs);
+
+END;
+$_$ LANGUAGE PLPGSQL;
+
+
+/* -- UNDO --
+
+BEGIN;
+DROP FUNCTION IF EXISTS action_trigger.purge_events();
+DROP TRIGGER IF EXISTS is_valid_retention_interval ON action_trigger.event_definition;
+DROP FUNCTION IF EXISTS action_trigger.check_valid_retention_interval();
+ALTER TABLE action_trigger.event_definition DROP COLUMN retention_interval;
+COMMIT;
+
+*/
+
+COMMIT;
+