[IMP] account: performances on total_invoiced field

The computation of total_invoiced field was very slow when the size of
account.invoice.report grows. This is due to usage of the field
user_currency_price_total that requires to build the full view (generates query
(id in []) for function field).

Using temporary SQL view (inspired by caf333e), directly filter the needed
items and avoid building the full table.

Fixes #6654

addons/account/partner.py

@@ -241,11 +241,46 @@ class res_partner(osv.osv):
     def _invoice_total(self, cr, uid, ids, field_name, arg, context=None):
         result = {}
         account_invoice_report = self.pool.get('account.invoice.report')
-        for partner in self.browse(cr, uid, ids, context=context):
-            domain = [('partner_id', 'child_of', partner.id), ('state', 'not in', ['draft', 'cancel'])]
-            invoice_ids = account_invoice_report.search(cr, uid, domain, context=context)
-            invoices = account_invoice_report.browse(cr, uid, invoice_ids, context=context)
-            result[partner.id] = sum(inv.user_currency_price_total for inv in invoices)
+        user = self.pool['res.users'].browse(cr, uid, uid, context=context)
+        user_currency_id = user.company_id.currency_id.id
+        for partner_id in ids:
+            all_partner_ids = self.pool['res.partner'].search(
+                cr, uid, [('id', 'child_of', partner_id)], context=context)
+
+            # searching account.invoice.report via the orm is comparatively expensive
+            # (generates queries "id in []" forcing to build the full table).
+            # In simple cases where all invoices are in the same currency than the user's company
+            # access directly these elements
+
+            # generate where clause to include multicompany rules
+            where_query = account_invoice_report._where_calc(cr, uid, [
+                ('partner_id', 'in', all_partner_ids), ('state', 'not in', ['draft', 'cancel'])
+            ], context=context)
+            account_invoice_report._apply_ir_rules(cr, uid, where_query, 'read', context=context)
+            from_clause, where_clause, where_clause_params = where_query.get_sql()
+
+            query = """ WITH currency_rate (currency_id, rate, date_start, date_end) AS (
+                                SELECT r.currency_id, r.rate, r.name AS date_start,
+                                    (SELECT name FROM res_currency_rate r2
+                                     WHERE r2.name > r.name AND
+                                           r2.currency_id = r.currency_id
+                                     ORDER BY r2.name ASC
+                                     LIMIT 1) AS date_end
+                                FROM res_currency_rate r
+                                )
+                      SELECT SUM(price_total * cr.rate) as total
+                        FROM account_invoice_report account_invoice_report, currency_rate cr
+                       WHERE %s
+                         AND cr.currency_id = %%s
+                         AND (COALESCE(account_invoice_report.date, NOW()) >= cr.date_start)
+                         AND (COALESCE(account_invoice_report.date, NOW()) < cr.date_end OR cr.date_end IS NULL)
+                    """ % where_clause
+
+            # price_total is in the currency with rate = 1
+            # total_invoice should be displayed in the current user's currency
+            cr.execute(query, where_clause_params + [user_currency_id])
+            result[partner_id] = cr.fetchone()[0]
+
         return result
 
     def _journal_item_count(self, cr, uid, ids, field_name, arg, context=None):