From: Tom Lane <tgl@sss.pgh.pa.us>
To: Bruce Momjian <bruce@momjian.us>
cc: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>,
        tsunakawa.takay@jp.fujitsu.com, GavinFlower@archidevsys.co.nz,
        robertmhaas@gmail.com, ideriha.takeshi@jp.fujitsu.com,
        pgsql-hackers@lists.postgresql.org, alvherre@alvh.no-ip.org,
        andres@anarazel.de, michael.paquier@gmail.com, david@pgmasters.net,
        Jim.Nasby@bluetreble.com, craig@2ndquadrant.com
Subject: Re: Protect syscache from bloating with negative cache entries
In-reply-to: <20190124144732.GD8334@momjian.us>
References: <20190121.172255.226467552.horiguchi.kyotaro@lab.ntt.co.jp>
 <20190123.173502.237450969.horiguchi.kyotaro@lab.ntt.co.jp>
 <20190123232145.GA8334@momjian.us>
 <20190124.183924.13894464.horiguchi.kyotaro@lab.ntt.co.jp>
 <20190124144732.GD8334@momjian.us>
Comments: In-reply-to Bruce Momjian <bruce@momjian.us>
	message dated "Thu, 24 Jan 2019 09:47:32 -0500"
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Date: Thu, 24 Jan 2019 09:59:52 -0500
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Bruce Momjian <bruce@momjian.us> writes:
> On Thu, Jan 24, 2019 at 06:39:24PM +0900, Kyotaro HORIGUCHI wrote:
>> I also thought that there's some other features that is useful if
>> it could be turned on remotely so the remote GUC feature but it
>> was too complex...

> Well, I am thinking if we want to do something like this, we should do
> it for all GUCs, not just for this one, so I suggest we not do this now
> either.

I will argue hard that we should not do it at all, ever.

There is already a mechanism for broadcasting global GUC changes:
apply them to postgresql.conf (or use ALTER SYSTEM) and SIGHUP.
I do not think we need something that can remotely change a GUC's
value in just one session.  The potential for bugs, misuse, and
just plain confusion is enormous, and the advantage seems minimal.

			regards, tom lane