remove explicit user permissions from messages where group already has access

db/migrate/20160112025852_remove_users_from_topic_allowed_users.rb

@@ -0,0 +1,20 @@
+class RemoveUsersFromTopicAllowedUsers < ActiveRecord::Migration
+
+  # historically we added admins automatically to a message if they
+  # responded, despite them being in the group the message is targetted at
+  # this causes inbox bloat for pretty much no reason
+  def up
+    sql = <<SQL
+    DELETE FROM topic_allowed_users tu
+    USING topic_allowed_groups tg
+    JOIN group_users gu ON gu.group_id = tg.group_id
+    WHERE tu.user_id = gu.user_id AND tg.topic_id = tu.topic_id
+SQL
+
+    execute sql
+  end
+
+  def down
+    # can not be reversed but can be replayed if needed
+  end
+end