Re: patch to allow disable of WAL recycling

Peter,

Thanks for your feedback. I'm happy to change the name of the tunable or to
update the man page in any way. I have already posted an updated patch
with changes to the man page which I think may address your concerns there,
but please let me know if that still needs more work. It looks like Kyotaro
already did some exploration, and tuning the min/max for the WAL size won't
solve this problem. Just let me know if there is anything else here which
you think I should look into.

Thanks again,
Jerry

On Tue, Jul 17, 2018 at 1:12 PM, Peter Eisentraut <
peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:

> On 17.07.18 00:04, Jerry Jelinek wrote:
> > There have been quite a few comments since last week, so at this point I
> > am uncertain how to proceed with this change. I don't think I saw
> > anything concrete in the recent emails that I can act upon.
>
> The outcome of this could be multiple orthogonal patches that affect the
> WAL file allocation behavior somehow. I think your original idea of
> skipping recycling on a COW file system is sound. But I would rather
> frame the option as "preallocating files is obviously useless on a COW
> file system" rather than "this will make things mysteriously faster with
> uncertain trade-offs".
>
> The actual implementation could use another round of consideration. I
> wonder how this should interact with min_wal_size. Wouldn't
> min_wal_size = 0 already do what we need (if you could set it to 0,
> which is currently not possible)? Should the new setting be something
> like min_wal_size = -1? Or even if it's a new setting, it might be
> better to act on it in XLOGfileslop(), so these things are kept closer
> together.
>
> --
> Peter Eisentraut http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>