Improve history handling on backend.

backend/resources/migrations/0009.history.improvements.up.sql

@@ -0,0 +1,42 @@
+DROP TRIGGER page_on_update_tgr ON pages;
+
+CREATE OR REPLACE FUNCTION handle_page_update()
+  RETURNS TRIGGER AS $pagechange$
+  BEGIN
+    --- Update projects modified_at attribute when a
+    --- page of that project is modified.
+    UPDATE projects SET modified_at = clock_timestamp()
+      WHERE id = OLD.project;
+
+    RETURN NEW;
+  END;
+$pagechange$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE FUNCTION handle_page_history()
+  RETURNS TRIGGER AS $pagehistory$
+  BEGIN
+    INSERT INTO pages_history (page, "user", created_at,
+                               modified_at, data, version)
+      VALUES (NEW.id, NEW."user", NEW.modified_at,
+              NEW.modified_at, NEW.data, NEW.version);
+
+    RETURN NEW;
+  END;
+$pagehistory$ LANGUAGE plpgsql;
+
+
+CREATE TRIGGER page_on_insert_tgr
+  AFTER INSERT ON pages
+  FOR EACH ROW
+  EXECUTE PROCEDURE handle_page_history();
+
+CREATE TRIGGER page_on_update_tgr
+  AFTER UPDATE ON pages
+  FOR EACH ROW
+  EXECUTE PROCEDURE handle_page_update();
+
+CREATE TRIGGER page_on_update_history_tgr
+  AFTER UPDATE ON pages
+  FOR EACH ROW
+  WHEN (OLD.data IS DISTINCT FROM NEW.data)
+  EXECUTE PROCEDURE handle_page_history();