CREATE TRIGGER "rtree_<t>_<c>_update1" AFTER UPDATE OF "<c>" ON "<t>"
  WHEN OLD."<i>" = NEW."<i>" AND
       (NEW."<c>" NOTNULL AND NOT ST_IsEmpty(NEW."<c>"))
BEGIN
  INSERT OR REPLACE INTO "rtree_<t>_<c>" VALUES (
    NEW."<i>",
    ST_MinX(NEW."<c>"), ST_MaxX(NEW."<c>"),
    ST_MinY(NEW."<c>"), ST_MaxY(NEW."<c>")
  );
END;