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Re: Wierd quirk of HS/SR, probably not fixable

From: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Wierd quirk of HS/SR, probably not fixable
Date: 2010-04-28 02:43:59
Message-ID: v2y3f0b79eb1004271943u65262e18je68fba81adbf6c77@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, Apr 28, 2010 at 4:12 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> Simon Riggs wrote:
>> On Tue, 2010-04-27 at 20:14 +0300, Heikki Linnakangas wrote:
>>> Simon Riggs wrote:
>>>> On Tue, 2010-04-27 at 18:13 +0300, Heikki Linnakangas wrote:
>>>>> Simon Riggs wrote:
>>>>>> If pg_stop_backup() is run it creates the .backup file in the archive.
>>>>>> In the absence of that file, we should be able to work out that
>>>>>> pg_stop_backup() was not run.
>>>>> It's just as likely that the file is there even though the backup didn't
>>>>> finish, though.
>>>> It's possible, but not likely. It would need to break at a very specific
>>>> place for that to be the case. Whereas the test I explained would work
>>>> for about 99% of the time between start and stop backup, except for the
>>>> caveat I explained also.
>>> I don't understand how you arrived at that figure.
>>
>> You're talking about the backup_label file, I'm talking about
>> the .backup file in the archive.
>
> Oh, the backup history file. We stopped relying on that with the
> introduction of the end-of-backup record, to make life easier for
> streaming replication, and because it's simpler anyway. I don't think we
> should go back to it.

Right.

When restore_command is not given, the backup history file would be
unavailable in the standby. We cannot regard the absence of the file
as non-run of pg_stop_backup().

Regards,

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

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