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From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
To: Andreas Pflug <pgadmin@pse-consulting.de>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Warm Standby restore_command documentation
Date: Mon, 20 Apr 2009 11:32:23 +0300
Message-ID: <49EC3317.7090209@enterprisedb.com> (raw)
In-Reply-To: <49E4D643.3050707@pse-consulting.de>
References: <3f0b79eb0903242329j12865d55s348f5c873a956e71@mail.gmail.com>
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	<3f0b79eb0904022042g35b8e3cah9432ff764e721a3@mail.gmail.com>
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	<3f0b79eb0904071817u5c32254ei61f7e68e54669d9e@mail.gmail.com>
	<49DDEE72.6030803@enterprisedb.com>
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	<49E4D643.3050707@pse-consulting.de>

Andreas Pflug wrote:
> I've been following the thread with growing lack of understanding why
> this is so hardly discussed, and I went back to the documentation of
> what the restore_command should do (
> http://www.postgresql.org/docs/8.3/static/warm-standby.html )
> 
> While the algorithm presented in the pseudocode isn't dealing too good
> with a situation where the trigger is set while the restore_command is
> sleeping (this should be handled better in a real implementation), the
> code says
> 
> "Restore all wal files. If no more wal files are present, stop restoring
> if the trigger is set; otherwise wait for a new wal file".
> 
> Since pg_standby is meant as implementation of restore_command, it has
> to follow the directive stated above; *anything else is a bug*.
> pg_standby currently does *not* obey this directive, and has that
> documented, but a documented bug still is a bug.

I think you're interpreting the chapter too strongly. The provided 
pseudo-code is just an example of a suitable restore_command, it doesn't 
say that pg_standby behaves exactly like that.

I agree we should change the default behavior, though.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com



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