Re: pg_xlog - files are guaranteed to be sequentialy named?

From: Johannes Konert <jkonert(at)t3go(dot)de>
To: pgsql-general(at)postgresql(dot)org
Subject: Re: pg_xlog - files are guaranteed to be sequentialy named?
Date: 2007-06-13 16:42:40
Message-ID: 46701E80.9020205@t3go.de
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Greg Smith wrote:
> He's talking about wiping out the ones on the backup server, so I
> think Johannes means erasing the old archived logs on the secondary
> here. That can screw up your backup if you do it wrong, but it's not
> an all-caps worthy mistake.
yes, that's what I am talking about related to
http://www.postgresql.org/docs/8.2/interactive/continuous-archiving.html.
Sorry, if that did not came out clearly enough.
>
> On Wed, 13 Jun 2007, Johannes Konert wrote:
>> Because I do not want to rely on creation-date,
>
> No, you want to rely on creation date, because then this problem goes
> away.
Truely right...if I can gurantee, that the file-dates of my archived
WAL-files do have proper timestamps. If the timestamps once are messed
up and all have the same timestamp (due to a Windows-copy or something
else foolish), then the delete-script might delete the wrong files...
> The idea you should be working toward is that you identify when your
> last base backup was started after it's copied to the secondary, and
> then you can safely delete any archived logs file on the secondary
> from before that time. Instead of doing "ls | sort -g -r" you should
> be doing something like looping over the files in a bash shell script
> and using
> [ -ot <first xlog in base backup> ] to determine which files to delete.
right; but as I said, then I rely on file-dates.
But during the day I came out with an solution: I store the WAL-files
with the time-stamp of archiving in their file-name. Thus I can order
and delete them safely.
Your hint was the one, that helped me to find that solution - so thanks
for that, Greg.....and the others.

Regards,
Johannes

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