Optimized StockService->GetProductDetails performance (fixes #2283)

migrations/0221.sql

@@ -0,0 +1,48 @@
+CREATE VIEW products_last_price
+AS
+SELECT
+	product_id,
+	MAX(purchased_date) AS purchased_date,
+	price -- Bare column, ref https://www.sqlite.org/lang_select.html#bare_columns_in_an_aggregate_query
+FROM stock_log
+WHERE transaction_type IN ('purchase', 'stock-edit-new', 'inventory-correction')
+	AND IFNULL(price, 0) > 0
+	AND IFNULL(amount, 0) > 0
+	AND undone = 0
+GROUP BY product_id;
+
+DROP VIEW products_last_purchased;
+CREATE VIEW products_last_purchased
+AS
+SELECT
+	1 AS id, -- Dummy, LessQL needs an id column
+	sl.product_id,
+	sl.amount,
+	sl.best_before_date,
+	sl.purchased_date,
+	IFNULL(plp.price, 0) AS price,
+	sl.location_id,
+	sl.shopping_location_id
+	FROM stock_log sl
+	JOIN (
+		SELECT
+			s1.product_id,
+			MAX(s1.id) max_stock_id
+			FROM stock_log s1
+			JOIN (
+					SELECT
+						s.product_id,
+						MAX(s.purchased_date) max_purchased_date
+					FROM stock_log s
+					WHERE undone = 0
+						AND transaction_type in ('purchase', 'stock-edit-new', 'inventory-correction')
+					GROUP BY s.product_id) sp2
+				ON s1.product_id = sp2.product_id
+				AND s1.purchased_date = sp2.max_purchased_date
+			WHERE undone = 0
+				AND transaction_type in ('purchase', 'stock-edit-new', 'inventory-correction')
+			GROUP BY s1.product_id) sp3
+		ON sl.product_id = sp3.product_id
+		AND sl.id = sp3.max_stock_id
+	LEFT JOIN products_last_price plp
+		ON sl.product_id = plp.product_id;