Re: shared-memory based stats collector

Hello.

At Wed, 20 Feb 2019 15:45:17 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote in <20190220(dot)154517(dot)24528798(dot)horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
> At Fri, 15 Feb 2019 15:53:28 -0300, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> wrote in <20190215185328(dot)GA29663(at)alvherre(dot)pgsql>
> > Talk about moving the whole file to another subdir ...
>
> Sounds reasonable. It was a searate patch at the first but
> currently melded to bloat the patch. I'm going to revert the
> separation/moving.

Done. This verison 16 looks as if the moving and splitting were
not happen. Major changes are:

- Restored old pgstats_* names. This largily shrinks the patch
size to less than a half lines of v15. More than that, it
gets easier to examine differences. (checkpointer.c and
bgwriter.c have a bit stale comments but it is an issue for
later.)

- Removed "oneshot" feature at all. This simplifies pgstat API
and let this patch far less simple.

- Moved StatsLock to LWTRANCHE_STATS, which is not necessary to
be in the main tranche.

- Fixed several bugs revealed by the shrinked size of the patch.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center