Re: checkpoints are duplicated even while the system is idle

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Thu, Oct 6, 2011 at 1:56 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I'm inclined to think that the way to deal with that is not to force out
>> useless WAL data, but to add some sort of explicit "I'm alive" heartbeat
>> signal to the walsender/walreceiver protocol. The hard part of that is
>> to figure out how to expose it where you can see it on the slave side
>> --- or do we have a status view that could handle that?

> As of 9.1, we already have something very much like this, in the
> opposite direction. See wal_receiver_status_interval and
> replication_timeout. I bet we could adapt that slightly to work in
> the other direction, too. But that'll only work with streaming
> replication - do we care about the WAL shipping case?

I can't get excited about the WAL-shipping case. The artifact that we'll
generate a checkpoint record every few minutes does not create enough
WAL volume for WAL-shipping to reliably generate a heartbeat signal.
It'd be way too long between filling up segments if that were the only
WAL data being generated.

regards, tom lane