add visual order to product_paint table (#445)

* add visual order to product_paint table

* rename

migrations/000.521.sql

@@ -0,0 +1,30 @@
+ALTER TABLE product_paint ADD COLUMN visual_order NUMERIC DEFAULT NULL;
+
+-- Contraint of visual_order per product_id
+ALTER TABLE product_paint ADD CONSTRAINT visual_order_per_productid UNIQUE (product_id, visual_order);
+
+-- Create function that will automatically assign a sequential visual_order to new rows if the visual_order is not provided
+-- in the insert.
+CREATE OR REPLACE FUNCTION enforce_sequential_visual_order()
+RETURNS TRIGGER AS $$
+DECLARE
+    max_visual_order INT;
+BEGIN
+    -- Get the current max value of visual_order for the given product_id
+    SELECT COALESCE(MAX(visual_order), -1) INTO max_visual_order
+    FROM product_paint
+    WHERE product_id = NEW.product_id;
+
+    -- Set visual_order to the next sequential number
+    NEW.visual_order := max_visual_order + 1;
+
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Activate the trigger
+CREATE TRIGGER enforce_sequential_visual_order
+BEFORE INSERT ON product_paint
+FOR EACH ROW
+WHEN (NEW.visual_order IS NULL) -- Only auto-assign if visual_order is not provided
+EXECUTE FUNCTION enforce_sequential_visual_order();