Date: Tue, 10 Dec 2013 10:38:48 +0100
From: Andres Freund <andres@2ndquadrant.com>
To: KONDO Mitsumasa <kondo.mitsumasa@lab.ntt.co.jp>
Cc: fabriziomello@gmail.com, Robert Haas <robertmhaas@gmail.com>,
 Simon Riggs <simon@2ndquadrant.com>,
 Pgsql Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Time-Delayed Standbys
Message-ID: <20131210093848.GG27840@awork2.anarazel.de>
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On 2013-12-10 13:26:27 +0900, KONDO Mitsumasa wrote:
> (2013/12/09 20:29), Andres Freund wrote:
> >On 2013-12-09 19:51:01 +0900, KONDO Mitsumasa wrote:
> >>Add my comment. We have to consider three situations.
> >>
> >>1. PITR
> >>2. replication standby
> >>3. replication standby with restore_command
> >>
> >>I think this patch cannot delay in 1 situation.
> >
> >Why?
> 
> I have three reasons.

None of these reasons seem to be of technical nature, right?

>   1. It is written in document. Can we remove it?
>   2. Name of this feature is "Time-delayed *standbys*", not "Time-delayed
>      *recovery*". Can we change it?

I don't think that'd be a win in clarity. But perhaps somebody else has
a better suggestion?

>   3. I think it is unnessesary in master PITR. And if it can delay in master
>      PITR, it will become master at unexpected timing, not to continue to
>      recovery. It is meaningless.

"master PITR"? What's that? All PITR is based on recovery.conf and thus
not really a "master"?

Why should we prohibit using this feature in PITR? I don't see any
advantage in doing so. If somebody doesn't want the delay, they
shouldn't set it in the configuration file. End of story.

There's not really a that meaningful distinction between PITR and
replication using archive_command. Especially when using
*pause_after. I think this feature will be used in a lot of scenarios in
which PITR is currently used.

Greetings,

Andres Freund

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


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