asset: cachezeit verkürzt

asset.py

@@ -8,7 +8,7 @@ from trytond.transaction import Transaction
 from trytond.pool import Pool
 from trytond.pyson import Eval, Bool, And, If, Date
 from trytond.report import Report
-from trytond.cache import Cache
+from trytond.cache import MemoryCache
 
 from decimal import Decimal
 from datetime import time
@@ -120,7 +120,7 @@ class Asset(SymbolMixin, ModelSQL, ModelView):
         readonly=True, model_name='investment.rate'),
         'get_rate_data')
 
-    _asset_cache = Cache('investment.asset.values', duration=6*3600, context=False)
+    _asset_cache = MemoryCache('investment.asset.values', duration=600, context=False)
 
     @classmethod
     def __register__(cls, module_name):
@@ -164,17 +164,6 @@ class Asset(SymbolMixin, ModelSQL, ModelView):
                 AssetSourceRel.create(to_create)
             asset_table.drop_column('updtsource')
 
-    @classmethod
-    def values_cache_clear(cls, id_assets, names):
-        """ set cache-values to None
-        """
-        for fname in names:
-            for id1 in id_assets:
-                cls._asset_cache.set('%(fname)s-%(id)d' % {
-                    'fname': fname,
-                    'id': id1,
-                    }, None)
-
     @classmethod
     def view_attributes(cls):
         return super().view_attributes() + [