From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Anastasia Lubennikova <a.lubennikova@postgrespro.ru>
Cc: Greg Nancarrow <gregn4422@gmail.com>
Cc: Peter Smith <smithpb2250@gmail.com>
Cc: Smith, Peter <peters@fast.au.fujitsu.com>
Cc: David Steele <david@pgmasters.net>
Cc: Tsunakawa, Takayuki <tsunakawa.takay@fujitsu.com>
Cc: Haribabu Kommi <kommi.haribabu@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: Dave Cramer <pg@fastcrypt.com>
Cc: Jing Wang <jingwangian@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Cc: Elvis Pranskevichus <elprans@gmail.com>
Subject: Re: Libpq support to connect to standby server as priority
Date: Tue, 24 Nov 2020 19:59:17 -0300
Message-ID: <20201124225917.GA21884@alvherre.pgsql> (raw)
In-Reply-To: <311787.1606254559@sss.pgh.pa.us>
On 2020-Nov-24, Tom Lane wrote:
> I'm inclined to go ahead and commit the 0001 patch I posted at [1]
> (ie, change the implementation of GUC_REPORT to avoid intra-query
> reports), since that addresses a performance problem that's
> independent of the goal here. The rest of this seems to still
> be in Greg's court.
Sounded a good idea to me.
> Has anyone got an opinion about the further improvement I suggested:
>
> >> As it stands, 0001 reduces the ParameterStatus message traffic to
> >> at most one per GUC per query, but it doesn't attempt to eliminate
> >> duplicate ParameterStatus messages altogether. We could do that
> >> as a pretty simple adjustment if we're willing to expend the storage
> >> to remember the last value sent to the client. It might be worth
> >> doing, since for example the function-SET-clause case would typically
> >> lead to no net change in the GUC's value by the end of the query.
>
> On reflection this seems worth doing, since excess client traffic
> is far from free.
Agreed. If this is just a few hundred bytes of server-side local memory
per backend, it seems definitely worth it.
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Cc: alvherre@alvh.no-ip.org, tgl@sss.pgh.pa.us, a.lubennikova@postgrespro.ru, gregn4422@gmail.com, smithpb2250@gmail.com, peters@fast.au.fujitsu.com, david@pgmasters.net, tsunakawa.takay@fujitsu.com, kommi.haribabu@gmail.com, robertmhaas@gmail.com, laurenz.albe@cybertec.at, pg@fastcrypt.com, jingwangian@gmail.com, elprans@gmail.com
Subject: Re: Libpq support to connect to standby server as priority
In-Reply-To: <20201124225917.GA21884@alvherre.pgsql>
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