rate: optimize for speed

rate.py

@@ -22,15 +22,14 @@ class Rate(SymbolMixin, ModelSQL, ModelView):
         depends=['asset_digits'])
 
     asset_digits = fields.Function(fields.Integer(string='Digits',
-        readonly=True), 'on_change_with_asset_digits')
+        readonly=True), 'get_rate_data')
     currency = fields.Function(fields.Many2One(string='Currency',
         readonly=True, model_name='currency.currency'),
-        'on_change_with_currency')
+        'get_rate_data')
     uom = fields.Function(fields.Many2One(string='Uom',
-        readonly=True, model_name='product.uom'),
-        'on_change_with_uom')
+        readonly=True, model_name='product.uom'), 'get_rate_data')
     symbol = fields.Function(fields.Char(string='Symbol',
-        readonly=True), 'on_change_with_symbol')
+        readonly=True), 'get_rate_data')
 
     @classmethod
     def __setup__(cls):
@@ -53,31 +52,39 @@ class Rate(SymbolMixin, ModelSQL, ModelView):
         IrDate = Pool().get('ir.date')
         return IrDate.today()
 
-    def on_change_with_symbol(self, name=None):
-        """ symbol:%
+    @classmethod
+    def get_rate_data(cls, rates, names):
+        """ speed up: get values for rate
         """
-        return '%'
+        pool = Pool()
+        Asset = pool.get('investment.asset')
+        tab_asset = Asset.__table__()
+        tab_rate = cls.__table__()
+        cursor = Transaction().connection.cursor()
 
-    @fields.depends('asset', '_parent_asset.uom')
-    def on_change_with_uom(self, name=None):
-        """ get unit of asset
-        """
-        if self.asset:
-            return self.asset.uom.id
+        query = tab_asset.join(tab_rate,
+                condition=tab_asset.id==tab_rate.asset,
+            ).select(
+                tab_rate.id,
+                tab_asset.uom,
+                tab_asset.currency,
+                tab_asset.currency_digits,
+                where=tab_rate.id.in_([x.id for x in rates]),
+            )
+        cursor.execute(*query)
+        records = cursor.fetchall()
 
-    @fields.depends('asset', '_parent_asset.currency')
-    def on_change_with_currency(self, name=None):
-        """ get currency
-        """
-        if self.asset:
-            return self.asset.currency.id
+        result = {x:{y.id: None for y in rates} for x in names}
+        for record in records:
+            r1 = {
+                'symbol': '%',
+                'uom': record[1],
+                'currency': record[2],
+                'asset_digits': record[3],
+                }
 
-    @fields.depends('asset', '_parent_asset.currency_digits')
-    def on_change_with_asset_digits(self, name=None):
-        """ get digits for asset
-        """
-        if self.asset:
-            return self.asset.currency_digits
-        return 4
+            for n in names:
+                result[n][record[0]] = r1[n]
+        return result
 
 # Rate