Re: Allow wal_keep_segments to keep all segments

Simon Riggs wrote:
> On Wed, 2010-06-02 at 15:20 -0400, Bruce Momjian wrote:
>
> > The attached patch allows wal_keep_segments = -1 to keep all segements;
> > this is particularly useful for taking a base backup, where you need all
> > the WAL files during startup of the standby. I have documented this
> > usage in the patch as well.
> >
> > I am thinking of applying this after 9.0 beta2 if there is no objection.
>
> It's not clear to me why "keep all files until server breaks" is a good
> setting. Surely you would set this parameter to the size of your disk.
> Why allow it to go higher?

Well, the -1 allows them to set it temporarily without having to compute
their free disk space. Frankly, because the disk space varies, it is
impossible to know exactly how large the disk is at the time it would
fill up.

I think the normal computation would be:

1) How long is my file system backup and restore to standby
going to take
2) How often do I generate a 16MB WAL file

You would do some computation to figure that out, then maybe multiply it
by 10x and set that for wal_keep_segments. I figured allowing a simple
-1 would be easier.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ None of us is going to be here forever. +