Re: shared-memory based stats collector

At Mon, 18 Feb 2019 21:35:31 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote in <20190218(dot)213531(dot)89078771(dot)horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
> I'm trying removing pgStatPendingTabHash it does't work yet. I'll
> include it in the next version.

Done. Passed a test for the case of internittent dshash lock
failure, which causes "pending" of local stats info.

- Removed pgStatPendingTabHash. "Pending" table entries are left
in pgStatTabList after pgstat_update_stat(). There's no longer
a "pending" stats store.

- Fixed several bugs of reading/writing at-rest file.

- Transactional snapshot behaved wrongly. Fixed it.

- In this project SQL helper functions are renamed from
pgstat_fetch_stat_* to backend_fetch_stat_* because the
functions with the similar cuntion are implemented for writer
side and they have the names of pgstat_fetch_stat_*.

But some of the functions had very confusing names that don't
follow the convention.

- Split pgStatLocalContext into pgSharedStatsContext and
pgStatSnapshotContext. The former is for shared statistics and
the latter is for transactional snapshot.

- Clean up pgstat.[ch] removing stale lines, fixing bogus comments.

This version is heavily improved from the previous version.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center