[check_postgres] Schema check is taking longer... why?

[Aleksey Tsalolikhin]

Our same schema check used to take under 10 seconds to run, but now
takes 8 - 45 seconds, and the time really varies.

Server and network loads appear the same, database load appears the
same...   what might make the schema check take longer?  What should I
look at?

Thanks,
-at