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Date: Tue, 14 Apr 2009 14:41:50 +0900
Message-ID: <3f0b79eb0904132241p18084914g792cb8e5ab3eebb3@mail.gmail.com>
Subject: Re: New trigger option of pg_standby
From: Fujii Masao <masao.fujii@gmail.com>
To: Simon Riggs <simon@2ndquadrant.com>
Cc: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>,
	Guillaume Smet <guillaume.smet@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>,
	Peter Eisentraut <peter_e@gmx.net>,
	Kevin Grittner <Kevin.Grittner@wicourts.gov>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
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Hi,

On Mon, Apr 13, 2009 at 2:52 PM, Fujii Masao <masao.fujii@gmail.com> wrote:
> But, a lookahead nextWALfile seems to work fine.
>
> if (triggered)
> {
> =A0 =A0if (smartMode && nextWALfile exists)
> =A0 =A0 =A0 =A0exit(0)
> =A0 =A0else
> =A0 =A0{
> =A0 =A0 =A0 =A0delete trigger file
> =A0 =A0 =A0 =A0exit(1)
> =A0 =A0}
> }

Umm... in this algorithm, the trigger file remains after failover
if the nextWALfile has the invalid record which means the end
of WAL files.

I'd like to propose another simple idea; pg_standby deletes the
trigger file *whenever* the nextWALfile is a timeline history file.
A timeline history file is restored at the end of recovery, so it's
guaranteed that the trigger file is deleted whether nextWALfile
exists or not.

A timeline history file is restored also at the beginning of
recovery, so the accidentally remaining trigger file is deleted
in early warm-standby as a side-effect of this idea.

How does that sound?

Regards,

--=20
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center