Add support for transitive unit conversions

migrations/0203.sql

@@ -0,0 +1,129 @@
+DROP VIEW IF EXISTS quantity_unit_conversions_resolved;
+
+CREATE VIEW quantity_unit_conversions_resolved AS
+WITH RECURSIVE
+	single(product_id, from_qu_id, to_qu_id, factor, source)
+AS (
+	-- 1. Product "purchase to stock" conversion factor
+	SELECT
+		p.id AS product_id,
+		p.qu_id_purchase AS from_qu_id,
+		p.qu_id_stock AS to_qu_id,
+		CASE WHEN p.qu_id_stock = p.qu_id_purchase THEN 1.0 ELSE p.qu_factor_purchase_to_stock END AS factor, -- Enforce a factor of 1 when QU stock = QU purchase
+		'1 product purchase to stock factor' AS source
+	FROM products p
+	UNION -- Inversed
+	SELECT
+		p.id AS product_id,
+		p.qu_id_stock AS from_qu_id,
+		p.qu_id_purchase AS to_qu_id,
+		1 / p.qu_factor_purchase_to_stock AS factor,
+		'1 product purchase to stock factor (inversed)' AS source
+	FROM products p
+	WHERE p.qu_id_stock != p.qu_id_purchase -- => Only when QU stock is not the same as QU purchase
+
+	UNION
+
+	-- 2. Product specific QU overrides
+	SELECT
+		p.id AS product_id,
+		quc.from_qu_id AS from_qu_id,
+		quc.to_qu_id AS to_qu_id,
+		quc.factor AS factor,
+		'2 product override' AS source
+	FROM products p
+	JOIN quantity_unit_conversions quc
+		ON p.id = quc.product_id
+
+	UNION
+
+	-- 3. Default (direct) QU conversion factors
+	SELECT
+		p.id AS product_id,
+		p.qu_id_stock AS from_qu_id,
+		quc.to_qu_id AS to_qu_id,
+		quc.factor AS factor,
+		'3 default direct factor' AS source
+	FROM products p
+	JOIN quantity_unit_conversions quc
+		ON p.qu_id_stock = quc.from_qu_id
+		AND quc.product_id IS NULL
+	JOIN quantity_units qu_from
+		ON quc.from_qu_id = qu_from.id
+	JOIN quantity_units qu_to
+		ON quc.to_qu_id = qu_to.id
+
+	UNION
+
+	-- 4. Default (indirect) QU conversion factors
+	SELECT
+		p.id AS product_id,
+		(SELECT from_qu_id FROM quantity_unit_conversions WHERE to_qu_id = quc.to_qu_id AND product_id = p.id) AS from_qu_id,
+		quc.from_qu_id AS to_qu_id,
+		(SELECT factor FROM quantity_unit_conversions WHERE to_qu_id = quc.to_qu_id AND product_id = p.id) / quc.factor AS factor,
+		'4 default indirect factor' AS source
+	FROM products p
+	JOIN product_qu_relations pqr
+		ON p.id = pqr.product_id
+	JOIN quantity_unit_conversions quc
+		ON pqr.qu_id = quc.from_qu_id
+		AND quc.product_id IS NULL
+	WHERE NOT EXISTS(SELECT 1 FROM quantity_unit_conversions qucx WHERE qucx.product_id = p.id AND qucx.from_qu_id = pqr.qu_id) -- => Product override exists
+),
+	closure(depth, product_id, path, from_qu_id, to_qu_id, factor, source)
+AS (
+	SELECT
+		1 as depth, product_id,
+		-- We need to keep track of the conversion path in order to prevent infinite loops
+		'/' || from_qu_id || '/' || to_qu_id || '/',
+		from_qu_id, to_qu_id,
+		factor, source
+	FROM single
+	
+	UNION
+	
+	SELECT
+		c.depth + 1, c.product_id,
+		c.path || s.to_qu_id || '/',
+		c.from_qu_id, s.to_qu_id,
+		c.factor * s.factor,
+		c.source || ' ~~> ' || s.source
+	FROM closure c
+	JOIN single s
+		ON  c.product_id = s.product_id
+		AND c.to_qu_id = s.from_qu_id
+	WHERE
+		c.path NOT LIKE ('%/' || s.to_qu_id || '/%')
+),
+	closure_rn(row_num, product_id, from_qu_id, to_qu_id, factor, source)
+AS (
+	SELECT
+		ROW_NUMBER() OVER(PARTITION BY product_id, from_qu_id, to_qu_id ORDER BY depth ASC),
+		product_id,
+		from_qu_id,
+		to_qu_id,
+		factor,
+		source
+	FROM closure
+)
+
+SELECT DISTINCT
+	-1 AS id, -- Dummy, LessQL needs an id column
+	c.product_id,
+	c.from_qu_id,
+	qu_from.name AS from_qu_name,
+	qu_from.name_plural AS from_qu_name_plural,
+	c.to_qu_id,
+	qu_to.name AS to_qu_name,
+	qu_to.name_plural AS to_qu_name_plural,
+	factor,
+	source
+FROM closure_rn c
+	JOIN quantity_units qu_from
+		ON c.from_qu_id = qu_from.id
+	JOIN quantity_units qu_to
+		ON c.to_qu_id = qu_to.id
+WHERE
+	c.row_num = 1
+ORDER BY
+	product_id, from_qu_id, to_qu_id;