--- a/schema/gemma.sql	Wed Nov 14 12:54:13 2018 +0100
+++ b/schema/gemma.sql	Wed Nov 14 13:12:41 2018 +0100
@@ -533,17 +533,28 @@
 CREATE TYPE waterway.log_type AS ENUM ('info', 'warn', 'error');
 
 CREATE TABLE waterway.import_logs (
-    import_id int NOT NULL REFERENCES waterway.imports(id),
+    import_id int NOT NULL REFERENCES waterway.imports(id) ON DELETE CASCADE,
     time timestamp NOT NULL DEFAULT now(),
     kind waterway.log_type NOT NULL DEFAULT 'info',
     msg TEXT NOT NULL
 );
 
 CREATE TABLE waterway.track_imports (
-    import_id int      NOT NULL REFERENCES waterway.imports(id),
+    import_id int      NOT NULL REFERENCES waterway.imports(id) ON DELETE CASCADE,
     relation  regclass NOT NULL,
     key       int      NOT NULL,
     UNIQUE (relation, key)
 );
 
+CREATE FUNCTION waterway.del_import() RETURNS trigger AS
+$$
+BEGIN
+    EXECUTE format('DELETE FROM %I WHERE id = $1', OLD.relation) USING OLD.key;
+END;
+$$
+LANGUAGE plpgsql;
+
+CREATE TRIGGER delete_import AFTER DELETE ON waterway.track_imports
+   FOR EACH ROW EXECUTE PROCEDURE waterway.del_import();
+
 COMMIT;