def collecting_queries_for_explain # :nodoc:
      current = Thread.current
      original, current[:available_queries_for_explain] = current[:available_queries_for_explain], []
      return yield, current[:available_queries_for_explain]
    ensure
      # Note that the return value above does not depend on this assigment.
      current[:available_queries_for_explain] = original
    end
def collecting_queries_for_explain # :nodoc:
      current = Thread.current
      original, current[:available_queries_for_explain] = current[:available_queries_for_explain], []
      return yield, current[:available_queries_for_explain]
    ensure
      # Note that the return value above does not depend on this assigment.
      current[:available_queries_for_explain] = original
    end
Relation#explain needs to be able to collect the queries regardless of
 whether auto explain is enabled. This method serves that purpose.