#464 related

arekit/contrib/utils/data/storages/row_cache.py

@@ -6,25 +6,36 @@ class RowCacheStorage(BaseRowsStorage):
     """ Row Caching storage kernel, based on python dictionary.
     """
 
-    def __init__(self):
+    def __init__(self, force_collect_columns=None):
+        """ This is a particular/related solution for the following issue:
+            https://github.com/nicolay-r/AREkit/issues/464
+            force_collect_columns: list
+                columns that supposed to be additionally considered in output.
+        """
+        assert(isinstance(force_collect_columns, list) or force_collect_columns is None)
         self.__f = None
         self.__row_cache = {}
         self.__columns = []
+        self.__force_collect_columns = [] if force_collect_columns is None else force_collect_columns
 
     @property
     def RowCache(self):
         return self.__row_cache
 
     def init_empty(self, columns_provider):
-        assert(isinstance(columns_provider, BaseColumnsProvider))
+        assert (isinstance(columns_provider, BaseColumnsProvider))
         for col_name, _ in columns_provider.get_columns_list_with_types():
             self.__columns.append(col_name)
 
+        # Expand with columns that are forced to be provided.
+        existed_set = set(self.__columns)
+        self.__columns += [c for c in self.__force_collect_columns if c not in existed_set]
+
     def iter_column_names(self):
         return iter(self.__columns)
 
     def _set_row_value(self, row_ind, column, value):
         self.__row_cache[column] = value
 
     def _begin_filling_row(self, row_ind):
-        self.__row_cache.clear()
+        self.__row_cache.clear(