Re: patch to allow disable of WAL recycling

Hi,

So here is the last set of benchmark results, this time from ext4 on a
small SATA-based RAID (3 x 7.2k). As before, I'm only attaching PDFs
with the simple charts, full results are available in the git repository
[1]. Overall the numbers are rather boring, with almost no difference
between the two setups.

That being said, I'm not opposed to introducing the GUC. I'm not going
to pretend my tests represents all possible HW configs and workloads,
and I have no trouble believing that it may be quite beneficial in some
cases.

The one comment about the code is that we usually use the actual default
value in the config sample. But the patch does this:

+#wal_recycle = off # do not recycle WAL files

while the GUC is defined like this:

{
{"wal_recycle", PGC_SUSET, WAL_SETTINGS,
gettext_noop("WAL recycling enabled."),
NULL
},
&wal_recycle,
true,
NULL, NULL, NULL
},

So the default is actually "on" which makes the commented-out config
sample rather confusing.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services