Horton

Re: walsender performance regression due to logical decoding on standby changes

Jeff Davis <pgsql@j-davis.com>

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From: Jeff Davis <pgsql@j-davis.com>
To: Andres Freund <andres@anarazel.de>, pgsql-hackers@postgresql.org, "Drouvot, Bertrand" <bertranddrouvot.pg@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>
Date: 2023-05-09T20:38:24Z
Lists: pgsql-hackers 
On Tue, 2023-05-09 at 12:02 -0700, Andres Freund wrote:
> I don't think the approach of not having any sort of "registry" of
> whether
> anybody is waiting for the replay position to be updated is
> feasible. Iterating over all walsenders slots is just too expensive -

Would it work to use a shared counter for the waiters (or, two
counters, one for physical and one for logical), and just early exit if
the count is zero?

Regards,
	Jeff Davis

Commits

  1. Optimize walsender wake up logic using condition variables

  2. For cascading replication, wake physical and logical walsenders separately