Store connection user_ids Auto Action

We are using a field called myconnections to store the user_ids of a users connections so that we can we can pass the array via REST. We update it with a code action but it doesn't seem to be working and I can't see why. The result of the following code is that nothing is ever stored in the field;

$user_id = $user->id;
if($user_id){
   $db   = JFactory::getDBO();
   $query = "SELECT id FROM #__comprofiler WHERE user_id = ".$user_id;
   $db->setQuery($query);
   $check_id = $db->loadResult();

   if($check_id){
        $query = "SELECT (REPLACE(REPLACE(asset,'.connection',''),'profile.','')) AS asset_user_id FROM #__comprofiler_plugin_activity WHERE user_id = ".$user_id;
        $db->setQuery($query);
        $cb_myconnections = $db->loadColumn();

        if($cb_myconnections){ $cb_myconnections = implode('|*|',$cb_myconnections); }

       $profile = new stdClass();
       $profile->id = $check_id;
       $profile->cb_myconnections = $cb_myconnections;
       $db->updateObject('#__comprofiler', $profile,'id');
   }
}

You shouldn't need to store them at all. Use a CB Query Field and query for that information then substitute your query field into your outbound REST usage (I assume you're using a Request action here?). The below for example will give you a comma separated list of user ids.

Query: Output: Multiple Rows
Columns: Single Column
Delimiter: Comma

Now you don't need to deal with duplicate data issues or synchronization issues.