Date: Thu, 12 Dec 2013 12:05:05 +0100
From: Andres Freund <andres@2ndquadrant.com>
To: Simon Riggs <simon@2ndQuadrant.com>
Cc: KONDO Mitsumasa <kondo.mitsumasa@lab.ntt.co.jp>,
 Pavel Stehule <pavel.stehule@gmail.com>,
 =?iso-8859-1?Q?Fabr=EDzio?= Mello <fabriziomello@gmail.com>,
 Robert Haas <robertmhaas@gmail.com>,
 Pgsql Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Time-Delayed Standbys
Message-ID: <20131212110505.GA14510@alap2.anarazel.de>
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On 2013-12-12 09:09:21 +0000, Simon Riggs wrote:
> >>     * Add functionality (I propose)
> >>     We can set negative number at min_standby_apply_delay. I think that
> >> this feature
> >>     is for world wide replication situation. For example, master server is
> >> in
> >>     Japan and slave server is in San Francisco. Japan time fowards than
> >> San
> >>     Francisco time
> >>     . And if we want to delay in this situation, it can need negative

> > This is because local time is recorded in XLOG. And it has big cost for
> > calculating global time.

Uhm? Isn't the timestamp in commit records actually a TimestampTz? And
thus essentially stored as UTC? I don't think this problem actually
exists?

> My suggestion would be to add the TZ to the checkpoint record. This
> way all users of WAL can see the TZ of the master and act accordingly.
> I'll do a separate patch for that.

Intuitively I'd say that might be useful - but I am not reall sure what
for. And we don't exactly have a great interface for looking at a
checkpoint's data. Maybe add it to the control file instead?

Greetings,

Andres Freund

-- 
 Andres Freund	                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


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