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Re: pg_stop_backup wait bug fix

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: pg_stop_backup wait bug fix
Date: 2008-12-03 08:24:40
Message-ID: 49364248.2090001@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-hackers
Fujii Masao wrote:
> On Wed, Dec 3, 2008 at 5:13 AM, Heikki Linnakangas
> <heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
>> Agreed, should use XLByteToPrevSeg. But I wonder if we can just replace the
>> current XLByteToSeg call with XLByteToPrevSeg? That would offset the return
>> value of the function by one byte as well, as well as the value printed to
>> the backup history file. In fact, I think the original patch got that wrong;
>> it would return the location of the *beginning* of the last xlog file.
> 
> You're right. As you say, the value (stopxlogfilename) printed to the backup
> history file is wrong. But, since the value is not used fortunately,
> any troubles
> have not come up. So, I think that we can just replace them.

Changing the return value doesn't seem like a good idea. If nothing 
else, it would be complicated to explain what it returns. I committed a 
patch that changes the waiting behavior, but not the return value or 
what's written into the backup label file,

>> I also noticed that the 2nd BackupHistoryFileName call in that function is
>> useless; histfilepath variable is already filled in earlier.
> 
> Somewhat confusingly, BackupHistoryFileName is called only once. Isn't 1st
> (which probably you thought) BackupHistoryFilePath?

Ouch, you're right. That's subtle.

> In order to prevent
> confusion, we should add new local variable (histfilename) for the backup
> history file name?

Agreed. I included that in the patch.

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

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