Creating reusable "filter_by_tags" function.

Moving the filtering-by-tag logic out of TagsFilter into a reusable function.

taiga/base/filters.py

@@ -19,6 +19,8 @@ from django.db.models import Q
 
 from rest_framework import filters
 
+from taiga.base.utils.db import filter_by_tags
+
 
 class QueryParamsFilterMixin(object):
     _special_values_dict = {
@@ -94,8 +96,6 @@ class IsProjectMemberFilterBackend(FilterBackend):
 
 
 class TagsFilter(FilterBackend):
-    FILTER_TAGS_SQL = "unpickle({table}.tags) && %s"
-
     def __init__(self, filter_name='tags'):
         self.filter_name = filter_name
 
@@ -108,7 +108,6 @@ class TagsFilter(FilterBackend):
     def filter_queryset(self, request, queryset, view):
         tags = self._get_tags_queryparams(request.QUERY_PARAMS)
         if tags:
-            where_sql = self.FILTER_TAGS_SQL.format(table=view.model._meta.db_table)
-            queryset = queryset.extra(where=[where_sql], params=[tags])
+            queryset = filter_by_tags(tags, queryset)
 
         return queryset

taiga/base/utils/db.py

@@ -0,0 +1,9 @@
+FILTER_TAGS_SQL = "unpickle({table}.tags) && %s"
+
+
+def filter_by_tags(tags, queryset):
+    """Filter a queryset of a model with pickled field named tags, by tags."""
+    table_name = queryset.model._meta.db_table
+    where_sql = FILTER_TAGS_SQL.format(table=table_name)
+
+    return queryset.extra(where=[where_sql], params=[tags])