class PgConn::SchemaMethods

def column_list_query(schema, relation)
  relation_clause = relation ? "relname = '#{relation}'" : nil
  [
      %(
        select  '#{schema}' || '.' || c.relname || '.' || a.attname
        from    pg_class c
        join    pg_attribute a on a.attrelid = c.oid
        where   relnamespace::regnamespace::text = '#{schema}'
        and     a.attnum > 0
      ),
      relation_clause
  ].compact.join(" and ")
end