diff --git a/taiga/projects/custom_attributes/migrations/0008_auto_20160728_0540.py b/taiga/projects/custom_attributes/migrations/0008_auto_20160728_0540.py
new file mode 100644
index 00000000..6f2d86f7
--- /dev/null
+++ b/taiga/projects/custom_attributes/migrations/0008_auto_20160728_0540.py
@@ -0,0 +1,118 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.2 on 2016-07-28 05:40
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('custom_attributes', '0007_auto_20160208_1751'),
+    ]
+
+    operations = [
+        # Function: Remove a key in a json field
+        migrations.RunSQL(
+            """
+            CREATE OR REPLACE FUNCTION "json_object_delete_keys"("json" json, VARIADIC "keys_to_delete" text[])
+                               RETURNS json
+                              LANGUAGE sql
+                             IMMUTABLE
+                                STRICT
+                                    AS $function$
+                       SELECT COALESCE ((SELECT ('{' || string_agg(to_json("key") || ':' || "value", ',') || '}')
+                                           FROM json_each("json")
+                                          WHERE "key" <> ALL ("keys_to_delete")),
+                                        '{}')::json $function$;
+            """,
+            reverse_sql="""DROP FUNCTION IF EXISTS "json_object_delete_keys"("json" json, VARIADIC "keys_to_delete" text[])
+                                           CASCADE;"""
+        ),
+
+        # Function: Romeve a key in the json field of *_custom_attributes_values.values
+        migrations.RunSQL(
+            """
+            CREATE OR REPLACE FUNCTION "clean_key_in_custom_attributes_values"()
+                               RETURNS trigger
+                                    AS $clean_key_in_custom_attributes_values$
+                               DECLARE
+                                       key text;
+                                       project_id int;
+                                       object_id int;
+                                       attribute text;
+                                       tablename text;
+                                       custom_attributes_tablename text;
+                                 BEGIN
+                                       key := OLD.id::text;
+                                       project_id := OLD.project_id;
+                                       attribute := TG_ARGV[0]::text;
+                                       tablename := TG_ARGV[1]::text;
+                                       custom_attributes_tablename := TG_ARGV[2]::text;
+
+                                       EXECUTE 'UPDATE ' || quote_ident(custom_attributes_tablename) || '
+                                                   SET attributes_values = json_object_delete_keys(attributes_values, ' || quote_literal(key) || ')
+                                                  FROM ' || quote_ident(tablename) || '
+                                                 WHERE ' || quote_ident(tablename) || '.project_id = ' || project_id || '
+                                                   AND ' || quote_ident(custom_attributes_tablename) || '.' || quote_ident(attribute) || ' = ' || quote_ident(tablename) || '.id';
+                                       RETURN NULL;
+                                   END; $clean_key_in_custom_attributes_values$
+                              LANGUAGE plpgsql;
+
+            """
+        ),
+
+        # Trigger: Clean userstorycustomattributes values before remove a userstorycustomattribute
+        migrations.RunSQL(
+            """
+            DROP TRIGGER IF EXISTS "update_userstorycustomvalues_after_remove_userstorycustomattribute"
+                                               ON custom_attributes_userstorycustomattribute
+                                          CASCADE;
+
+            CREATE TRIGGER "update_userstorycustomvalues_after_remove_userstorycustomattribute"
+           AFTER DELETE ON custom_attributes_userstorycustomattribute
+              FOR EACH ROW
+         EXECUTE PROCEDURE clean_key_in_custom_attributes_values('user_story_id', 'userstories_userstory', 'custom_attributes_userstorycustomattributesvalues');
+            """
+        ),
+
+        # Trigger: Clean taskcustomattributes values before remove a taskcustomattribute
+        migrations.RunSQL(
+            """
+            DROP TRIGGER IF EXISTS "update_taskcustomvalues_after_remove_taskcustomattribute"
+                                               ON custom_attributes_taskcustomattribute
+                                          CASCADE;
+
+            CREATE TRIGGER "update_taskcustomvalues_after_remove_taskcustomattribute"
+           AFTER DELETE ON custom_attributes_taskcustomattribute
+              FOR EACH ROW
+         EXECUTE PROCEDURE clean_key_in_custom_attributes_values('task_id', 'tasks_task', 'custom_attributes_taskcustomattributesvalues');
+            """
+        ),
+
+        # Trigger: Clean issuecustomattributes values before remove a issuecustomattribute
+        migrations.RunSQL(
+            """
+            DROP TRIGGER IF EXISTS "update_issuecustomvalues_after_remove_issuecustomattribute"
+                                               ON custom_attributes_issuecustomattribute
+                                          CASCADE;
+
+            CREATE TRIGGER "update_issuecustomvalues_after_remove_issuecustomattribute"
+           AFTER DELETE ON custom_attributes_issuecustomattribute
+              FOR EACH ROW
+         EXECUTE PROCEDURE clean_key_in_custom_attributes_values('issue_id', 'issues_issue', 'custom_attributes_issuecustomattributesvalues');
+            """
+        ),
+        migrations.AlterIndexTogether(
+            name='issuecustomattributesvalues',
+            index_together=set([('issue',)]),
+        ),
+        migrations.AlterIndexTogether(
+            name='taskcustomattributesvalues',
+            index_together=set([('task',)]),
+        ),
+        migrations.AlterIndexTogether(
+            name='userstorycustomattributesvalues',
+            index_together=set([('user_story',)]),
+        ),
+    ]
diff --git a/taiga/projects/custom_attributes/models.py b/taiga/projects/custom_attributes/models.py
index d7e4e32c..5fe3c6a0 100644
--- a/taiga/projects/custom_attributes/models.py
+++ b/taiga/projects/custom_attributes/models.py
@@ -101,6 +101,7 @@ class UserStoryCustomAttributesValues(AbstractCustomAttributesValues):
     class Meta(AbstractCustomAttributesValues.Meta):
         verbose_name = "user story ustom attributes values"
         verbose_name_plural = "user story custom attributes values"
+        index_together = [("user_story",)]
 
     @property
     def project(self):
@@ -116,6 +117,7 @@ class TaskCustomAttributesValues(AbstractCustomAttributesValues):
     class Meta(AbstractCustomAttributesValues.Meta):
         verbose_name = "task ustom attributes values"
         verbose_name_plural = "task custom attributes values"
+        index_together = [("task",)]
 
     @property
     def project(self):
@@ -131,6 +133,7 @@ class IssueCustomAttributesValues(AbstractCustomAttributesValues):
     class Meta(AbstractCustomAttributesValues.Meta):
         verbose_name = "issue ustom attributes values"
         verbose_name_plural = "issue custom attributes values"
+        index_together = [("issue",)]
 
     @property
     def project(self):