At Mon, 12 Feb 2018 22:28:15 +0900, Michael Paquier <mich...@paquier.xyz> wrote 
in <20180212132815.gb18...@paquier.xyz>
> On Fri, Feb 09, 2018 at 05:08:23PM +0900, Kyotaro HORIGUCHI wrote:
> > > postgres: max_wal_senders must be less than max_connections
> > 
> > I think that we can safely increase the fallback value to 20 with
> > which regtests are known not to fail. I believe that is
> > preferable than explicitly reducing max_wal_senders in the
> > generated config file. I confirmed that tegtest won't fail with
> > the value. (Except with permanent failure of dynamic shared
> > memory)
> I would vote for just removing the minimum check at 10 connections as
> you do.  It is not worth the code complication in initdb to decrease
> max_wal_senders if max_connections is set to 10, which does not happen

Definitely. The another rationale for the value is that regtest
fails with the numbers less than 20. So it's not 11 but
20. Currently regtest should succeed with that number of
connections as written in parallel_schedule and I've read (in
Robert's mail, but I haven't confirmed) that tests for parallel
scans are designed to use up to 20 connections.

> even on definitely-not-decent hardware of those days like a RPI
> (memories from my hamster, RIP, which set max_connections to 100). 

I believe it is the minimal box where anyone casulally try to run
PostgreSQL as is.


Kyotaro Horiguchi
NTT Open Source Software Center

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