CREATE
OR REPLACE FUNCTION prevent_cycle()
RETURNS TRIGGER AS '
DECLARE
has_cycle BOOLEAN;
BEGIN
WITH RECURSIVE chain AS (SELECT id, parent_asset_id
FROM asset
WHERE id = NEW.parent_asset_id
UNION ALL
SELECT a.id, a.parent_asset_id
FROM asset a
JOIN chain c ON a.id = c.parent_asset_id)
SELECT EXISTS (SELECT 1 FROM chain WHERE id = NEW.id)
INTO has_cycle;
IF
has_cycle THEN
RAISE EXCEPTION ''Circular reference detected for asset %'', NEW.id;
END IF;
RETURN NEW;
END;
'
LANGUAGE plpgsql;
CREATE TRIGGER asset_no_cycle
BEFORE INSERT OR
UPDATE ON asset
FOR EACH ROW
WHEN (NEW.parent_asset_id IS NOT NULL)
EXECUTE FUNCTION prevent_cycle();
CREATE
OR REPLACE FUNCTION prevent_cycle()
RETURNS TRIGGER AS '
DECLARE
has_cycle BOOLEAN;
BEGIN
WITH RECURSIVE chain AS (SELECT id, parent_location_id
FROM location
WHERE id = NEW.parent_location_id
UNION ALL
SELECT a.id, a.parent_location_id
FROM location a
JOIN chain c ON a.id = c.parent_location_id)
SELECT EXISTS (SELECT 1 FROM chain WHERE id = NEW.id)
INTO has_cycle;
IF
has_cycle THEN
RAISE EXCEPTION ''Circular reference detected for location %'', NEW.id;
END IF;
RETURN NEW;
END;
'
LANGUAGE plpgsql;
CREATE TRIGGER location_no_cycle
BEFORE INSERT OR
UPDATE ON location
FOR EACH ROW
WHEN (NEW.parent_location_id IS NOT NULL)
EXECUTE FUNCTION prevent_cycle();
ALTER FUNCTION prevent_cycle RENAME TO prevent_location_cycle;
DROP TRIGGER asset_no_cycle ON asset;
CREATE
OR REPLACE FUNCTION prevent_asset_cycle()
RETURNS TRIGGER AS '
DECLARE
has_cycle BOOLEAN;
BEGIN
WITH RECURSIVE chain AS (SELECT id, parent_asset_id
FROM asset
WHERE id = NEW.parent_asset_id
UNION ALL
SELECT a.id, a.parent_asset_id
FROM asset a
JOIN chain c ON a.id = c.parent_asset_id)
SELECT EXISTS (SELECT 1 FROM chain WHERE id = NEW.id)
INTO has_cycle;
IF
has_cycle THEN
RAISE EXCEPTION ''Circular reference detected for asset %'', NEW.id;
END IF;
RETURN NEW;
END;
'
LANGUAGE plpgsql;
CREATE TRIGGER asset_no_cycle
BEFORE INSERT OR
UPDATE ON asset
FOR EACH ROW
WHEN (NEW.parent_asset_id IS NOT NULL)
EXECUTE FUNCTION prevent_asset_cycle();