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
