Message-ID: <496F5502.4020907@enterprisedb.com>
Date: Thu, 15 Jan 2009 17:23:46 +0200
From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Organization: EnterpriseDB
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To: Fujii Masao <masao.fujii@gmail.com>
CC: Bruce Momjian <bruce@momjian.us>, Randy Isbell <jisbell@cisco.com>,
	pgsql-bugs@postgresql.org
Subject: Re: BUG #4566: pg_stop_backup() reports incorrect STOP WAL
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References: <200901150150.n0F1oV113850@momjian.us>	
	<496F2795.70105@enterprisedb.com>
	<3f0b79eb0901150615g133f845erc39faf19793d5977@mail.gmail.com>
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Fujii Masao wrote:
> On Thu, Jan 15, 2009 at 9:09 PM, Heikki Linnakangas
> <heikki.linnakangas@enterprisedb.com> wrote:
>> 1. The proposed patch would remove the "+ 1". Seems like an unnecessary API
>> change, and I don't recall any reason why the new definition would be
>> better.
> 
> My patch doesn't change the return value of pg_stop_backup(), it's still
> the same as the return value of pg_switch_xlog(). 

Oh, ok.

> Only a part of backup
> history file (the file name including stop wal location) is changed.
> Currently, the file name is wrong if stop wal location indicates a boundary
> byte. This would confuse the user, I think.

Hmm, I guess that would make it less confusing. Seems quite dangerous to 
change the meaning now, however :-(. A program (or person) that knows 
its current meaning would currently wait for STOP WAL filename - 1 file 
to be archived. If we change the meaning, the same program would 
determine that the backup is safe, even if the last xlog file hasn't yet 
been archived. So I think this is not back-portable.

Should we change it in HEAD? I'm leaning towards no, on the grounds that 
tools/people would then have to know the version it's dealing with to 
interpret the value correctly, and because pg_stop_backup() now waits 
for the last xlog file to be archived before returning, there's little 
need to look at that file.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com