Re: shared-memory based stats collector

Hello. This is rebased version.

At Thu, 8 Nov 2018 16:06:49 +0100, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote in <de249c3f-79c9-b75c-79a3-5e2d008548a8(at)2ndquadrant(dot)com>
> However a quite a few extensions in contrib seem are broken now. It
> seems fixing it is as simple as including the new bestatus.h next to
> pgstat.h.

The additional 0009 does that.

At Thu, 8 Nov 2018 12:39:41 -0300, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> wrote in <20181108153941(dot)txjb6rg3y7q26ldm(at)alvherre(dot)pgsql>
> On 2018-Nov-08, Tomas Vondra wrote:
>
> > I'm not sure splitting the headers like this is needed, actually. It's true
> > we're replacing pgstat.c with something else, but it's still related to
> > stats, backing pg_stat_* system views etc. So I'd keep as much of the
> > definitions in pgstat.h, so that it's enough to include that one header
> > file. That would "unbreak" the extensions.
>
> pgstat.h includes a lot of other stuff that presumably isn't needed if
> all some .c wants is in bestatus.h, so my vote would be to make this
> change *if it's actually possible to do it*: you want the affected
> headers to compile standalone (use cpluspluscheck or similar to verify
> this), for one thing.

cpluspluscheck doesn't complain to this change. I'm afraid that I
didn't read you cleary, but I counted up files that needs only
pgstat/ only bestatus / both in $(TOPDIR). (containing contrib)

only (new) pgstat.h : 33
only bestatus.h : 47
both : 22

> > Renaming pgstat_report_* functions to bestatus_report_* seems unnecessary to
> > me too. The original names seem quite fine to me.
>
> Yeah, this probably keeps churn to a minimum.

Reverted the names. pgstat_intialize() and
pgstat_clear_snapshot() were splitted into two functions for each
pgstat.c and bestatus.c. (and pgstat_clear_snapstop() is calling
pgstat_bestatus_clear_snapshot()!, and the names of the functions
looks somewhat inconsistent. Will fix later.)

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center