[FIX] stock_account: stock valuation report performances

Basically, computation of the `inventory_value` is now done
in batch instead of one by one.

In a real use case, the computation of the stock valuation
passed from 20+ minutes to less than a minute.

This revision contains an unusual SQL request:
`SELECT DISTINCT ON`
Basically, it returns the most recent line of table
product_price_history for each tuple
`(product_template_id, company_id)`
which is actually what we want, with good performances.

See postgresql doc for more information:
http://www.postgresql.org/docs/9.0/static/sql-select.html#SQL-DISTINCT

opw-641154

addons/stock_account/wizard/stock_valuation_history.py

@@ -46,21 +46,39 @@ def read_group(self, cr, uid, domain, fields, groupby, offset=0, limit=None, con
         if context is None:
             context = {}
         date = context.get('history_date')
-        prod_dict = {}
         if 'inventory_value' in fields:
+            group_lines = {}
+            for line in res:
+                domain = line.get('__domain', [])
+                group_lines.setdefault(str(domain), self.search(cr, uid, domain, context=context))
+            line_ids = set()
+            for ids in group_lines.values():
+                for product_id in ids:
+                    line_ids.add(product_id)
+            line_ids = list(line_ids)
+            cr.execute('SELECT id, product_id, price_unit_on_quant, company_id, quantity FROM stock_history WHERE id in %s', (tuple(line_ids),))
+            lines_rec = cr.dictfetchall()
+            lines_dict = dict((line['id'], line) for line in lines_rec)
+            product_ids = list(set(line_rec['product_id'] for line_rec in lines_rec))
+            products_rec = self.pool['product.product'].read(cr, uid, product_ids, ['cost_method', 'product_tmpl_id'], context=context)
+            products_dict = dict((product['id'], product) for product in products_rec)
+            cost_method_product_tmpl_ids = list(set(product['product_tmpl_id'][0] for product in products_rec if product['cost_method'] != 'real'))
+            cr.execute('SELECT DISTINCT ON (product_template_id, company_id) product_template_id, company_id, cost FROM product_price_history WHERE product_template_id in %s AND datetime <= %s ORDER BY product_template_id, company_id, datetime DESC', (tuple(cost_method_product_tmpl_ids), date))
+            histories = cr.dictfetchall()
+            histories_dict = {}
+            for history in histories:
+                histories_dict[(history['product_template_id'], history['company_id'])] = history['cost']
             for line in res:
-                lines = self.search(cr, uid, line.get('__domain', []), context=context)
                 inv_value = 0.0
-                product_tmpl_obj = self.pool.get("product.template")
-                lines_rec = self.browse(cr, uid, lines, context=context)
-                for line_rec in lines_rec:
-                    if line_rec.product_id.cost_method == 'real':
-                        price = line_rec.price_unit_on_quant
+                lines = group_lines.get(str(line.get('__domain', [])))
+                for line_id in lines:
+                    line_rec = lines_dict[line_id]
+                    product = products_dict[line_rec['product_id']]
+                    if product['cost_method'] == 'real':
+                        price = line_rec['price_unit_on_quant']
                     else:
-                        if not line_rec.product_id.id in prod_dict:
-                            prod_dict[line_rec.product_id.id] = product_tmpl_obj.get_history_price(cr, uid, line_rec.product_id.product_tmpl_id.id, line_rec.company_id.id, date=date, context=context)
-                        price = prod_dict[line_rec.product_id.id]
-                    inv_value += price * line_rec.quantity
+                        price = histories_dict.get((product['product_tmpl_id'][0], line_rec['company_id']), 0.0)
+                    inv_value += price * line_rec['quantity']
                 line['inventory_value'] = inv_value
         return res