Re: wake up logical workers after ALTER SUBSCRIPTION

I spent some more time on the prevent-unnecessary-wakeups patch for
logical/worker.c that I've been alluding to in this thread, and I found a
few more places where we depend on the worker periodically waking up.  This
seems to be a common technique, so I'm beginning to wonder whether these
changes are worthwhile.  I think there's a good chance it would become a
game of whac-a-mole.

-- 
Nathan Bossart
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