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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Michael Paquier <michael@paquier.xyz>
Cc: Tsunakawa, Takayuki <tsunakawa.takay@jp.fujitsu.com>
Cc: Dave Cramer <pg@fastcrypt.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: laurenz.albe@cybertec.at <laurenz.albe@cybertec.at>
Cc: Haribabu Kommi <kommi.haribabu@gmail.com>
Cc: Jing Wang <jingwangian@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Libpq support to connect to standby server as priority
Date: Mon, 14 Jan 2019 21:53:17 -0500
Message-ID: <30679.1547520797@sss.pgh.pa.us> (raw)
In-Reply-To: <20190115024855.GC1433@paquier.xyz>
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	<20190115024855.GC1433@paquier.xyz>

Michael Paquier <michael@paquier.xyz> writes:
> On Tue, Jan 15, 2019 at 02:00:57AM +0000, Tsunakawa, Takayuki wrote:
>> The original desire should have been the ability to connect to a
>> primary or a standby.  So, I think we should go back to the original
>> thinking (and not complicate the feature), and create a read only
>> GUC_REPORT variable, say, server_role, that identifies whether the
>> server is a primary or a standby. 

> From the point of view of making sure that a client is really
> connected to  a primary or a standby, this is the best idea around.

There are a couple of issues here:

1. Are you sure there are no use-cases for testing transaction_read_only
as such?

2. What will the fallback implementation be, when connecting to a server
too old to have the variable you want?

			regards, tom lane




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  Cc: tgl@sss.pgh.pa.us, michael@paquier.xyz, tsunakawa.takay@jp.fujitsu.com, pg@fastcrypt.com, robertmhaas@gmail.com, laurenz.albe@cybertec.at, kommi.haribabu@gmail.com, jingwangian@gmail.com
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