def delete_by_query(query)
      rsp = post("<delete><query>#{query}</query></delete>")
      success?(rsp.body) or log_error(rsp.body)
    end
def delete_by_query(query)
      rsp = post("<delete><query>#{query}</query></delete>")
      success?(rsp.body) or log_error(rsp.body)
    end
deletes documents matching <tt>query</tt> from the index