diff --git a/shopelectro/context.py b/shopelectro/context.py
index eceb304c..6022899a 100644
--- a/shopelectro/context.py
+++ b/shopelectro/context.py
@@ -62,16 +62,18 @@ def merge_products_context(products):
 
 class ObjectsComposition:
 
-    super = object()
+    super: 'ObjectsComposition' = None
 
     # TODO - resolve objects good piping
-    def __or__(self, other):
-        self.super = other
-        return self
+    def __or__(self, other: 'ObjectsComposition'):
+        other.super = self
+        return other
 
 
 class AbstractContext(ObjectsComposition):
 
+    super: 'AbstractContext' = None
+
     def __init__(
         self,
         # TODO slug maybe part of url_kwargs
@@ -108,7 +110,11 @@ def get_context_data(self) -> typing.Dict[str, typing.Any]:
         raise NotImplementedError
 
 
+# TODO make it ABC or smth
 class ProductsListContext(AbstractContext):
+
+    super: 'ProductsListContext' = None
+
     @property
     def products(self) -> QuerySet:
         raise NotImplementedError
@@ -188,12 +194,49 @@ def get_context_data(self):
         }
 
 
+class DBTemplateContext(AbstractContext):
+    """Processes some page data fields as templates with each own context."""
+
+    @property
+    @lru_cache(maxsize=1)
+    def page(self):
+        page = self.super.page
+        context = self.get_super_context_data()
+
+        def template_context(page, tag_titles, tags):
+            return {
+                'page': page,
+                'tag_titles': tag_titles,
+                'tags': tags,
+            }
+
+        tags = context['tags']
+        if tags:
+            # TODO - move to QuerySet
+            tag_titles = models.serialize_tags_to_title(tags)
+            page.get_template_render_context = partial(
+                template_context, page, tag_titles, tags
+            )
+
+        return page
+
+    @lru_cache(maxsize=1)
+    def get_super_context_data(self):
+        """Just for cache."""
+        return self.super.get_context_data()
+
+    @lru_cache(maxsize=1)
+    def get_context_data(self):
+        return {
+            **self.get_super_context_data(),
+            'page': self.page,
+        }
+
+
 # class PaginatedCatalogContext:
 #     ...
 #
 #
-# class DBTemplateContext:
-#     ...
 #
 #
 # class CatalogView:
diff --git a/shopelectro/models.py b/shopelectro/models.py
index 427e0d83..1d2ca44f 100644
--- a/shopelectro/models.py
+++ b/shopelectro/models.py
@@ -326,6 +326,9 @@ def serialize_tags(
     type_delimiter: str,
     group_delimiter: str,
 ) -> str:
+    if not tags:
+        return ''
+
     group_tags_map = tags.get_group_tags_pairs()
 
     _, tags_by_group = zip(*group_tags_map)
diff --git a/shopelectro/views/catalog.py b/shopelectro/views/catalog.py
index 7a102dbf..bda3cf8f 100644
--- a/shopelectro/views/catalog.py
+++ b/shopelectro/views/catalog.py
@@ -189,8 +189,12 @@ def get_products(self) -> QuerySet:
 
     def get_context_data(self, **kwargs):
         """Add sorting options and view_types in context."""
-        context_ = context.TaggedCategoryContext() | context.CategoryContext(
-            self.object.slug, kwargs, self.request
+        context_ = (
+            context.CategoryContext(
+                self.object.slug, self.kwargs, self.request
+            )
+            | context.TaggedCategoryContext()
+            | context.DBTemplateContext()
         )
         return {
             **super().get_context_data(**kwargs),
@@ -198,43 +202,7 @@ def get_context_data(self, **kwargs):
         }
 
 
-class DBContextCategoryPage(CategoryPage):
-    """Process db page data as db context."""
-
-    def get_tags(self) -> typing.Optional[models.TagQuerySet]:
-
-        @lru_cache(maxsize=64)
-        def get_tags(request_tags_: str):
-            slugs = models.Tag.parse_url_tags(request_tags_)
-            return models.Tag.objects.filter(slug__in=slugs)
-
-        request_tags = self.kwargs.get('tags')
-        if not request_tags:
-            return None
-        return get_tags(request_tags)
-
-    def get_object(self, queryset=None):
-        page = super().get_object(queryset)
-
-        def template_context(page, tag_titles, tags):
-            return {
-                'page': page,
-                'tag_titles': tag_titles,
-                'tags': tags,
-            }
-
-        tags = self.get_tags()
-        if tags:
-            # TODO - move to QuerySet
-            tag_titles = models.serialize_tags_to_title(tags)
-            page.get_template_render_context = partial(
-                template_context, page, tag_titles, tags
-            )
-
-        return page
-
-
-class SortingCategoryPage(DBContextCategoryPage):
+class SortingCategoryPage(CategoryPage):
 
     def get_products(self) -> QuerySet:
         sorting_index = int(self.kwargs.get('sorting', 0))