I've attached a small patch that remove unused parameter 'rel' from the static function lookup_var_attr_stats() in extended_stats.c
While exploring src/backend/statistics, I noticed that there are several other parameters which appear to be unused. However, since the discussion around import/export statistics [1] attribute_stats.c is still ongoing and many functions from other files are non-static, those parameters may yet prove useful. Therefore, I'm only removing the parameter from this static function.