Re: Recovery target 'immediate'

From: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Magnus Hagander <magnus(at)hagander(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Recovery target 'immediate'
Date: 2013-04-26 16:25:12
Message-ID: 517AAA68.6040006@vmware.com
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On 26.04.2013 19:05, Simon Riggs wrote:
> On 26 April 2013 16:38, Robert Haas<robertmhaas(at)gmail(dot)com> wrote:
>> On Fri, Apr 26, 2013 at 11:35 AM, Simon Riggs<simon(at)2ndquadrant(dot)com> wrote:
>>> Given that I was describing how we might implement Heikki's
>>> suggestion, I find this comment confusing.
>>>
>>> Please explain.
>>
>> Heikki's suggestion is simply to have a mode that stops as soon as
>> consistency is reached. The server already knows (from the backup
>> label) what the consistency point is, so there's no need to add a
>> restore point or anything else to the WAL stream to implement what
>> he's talking about.
>
> Using restore points just puts into use the facility that is already
> best practice to use, put there for just this kind of situation.
> I guess you could do recovery_target_name = '$consistent'
>
> Doing it the other way means you need to add a new kind of recovery
> target to the API just for this.
> recovery_target_immediate = on

Sounds good to me.

Actually, from a usability point of view I think would be nice to have
just one setting, "recovery_target". It's already somewhat confusing to
have recovery_target_xid, recovery_target_time, and
recovery_target_name, which are mutually exclusive, and
recovery_target_inclusive which is just a modifier for the others. Maybe
something like:

recovery_target = 'xid 1234'
recovery_target = 'xid 1234 exclusive'
recovery_target = '2013-04-22 12:33'
recovery_target = '2013-04-22 12:33 exclusive'
recovery_target = 'consistent'
recovery_target = 'name: daily backup'

- Heikki

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