Re: Improving connection scalability: GetSnapshotData()

From: Andres Freund <andres(at)anarazel(dot)de>
To: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Cc: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Daniel Gustafsson <daniel(at)yesql(dot)se>, Robert Haas <robertmhaas(at)gmail(dot)com>, "Jonathan S(dot) Katz" <jkatz(at)postgresql(dot)org>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Peter Geoghegan <pg(at)bowt(dot)ie>, Bruce Momjian <bruce(at)momjian(dot)us>, David Rowley <dgrowleyml(at)gmail(dot)com>
Subject: Re: Improving connection scalability: GetSnapshotData()
Date: 2020-08-12 17:38:55
Message-ID: 20200812173855.s4co5jz67z7tlnl7@alap3.anarazel.de
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Hi,

On 2020-08-12 12:24:52 +1200, Thomas Munro wrote:
> On Wed, Aug 12, 2020 at 12:19 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > On 2020-07-29 19:20:04 +1200, Thomas Munro wrote:
> > > On Wed, Jul 29, 2020 at 6:15 PM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> > > > +static inline FullTransactionId
> > > > +FullXidViaRelative(FullTransactionId rel, TransactionId xid)
> > > >
> > > > I'm struggling to find a better word for this than "relative".
> > >
> > > The best I've got is "anchor" xid. It is an xid that is known to
> > > limit nextFullXid's range while the receiving function runs.
> >
> > Thinking about it, I think that relative is a good descriptor. It's just
> > that 'via' is weird. How about: FullXidRelativeTo?
>
> WFM.

Cool, pushed.

Attached are the rebased remainder of the series. Unless somebody
protests, I plan to push 0001 after a bit more comment polishing and
wait a buildfarm cycle, then push 0002-0005 and wait again, and finally
push 0006.

There's further optimizations, particularly after 0002 and after 0006,
but that seems better done later.

Greetings,

Andres Freund

Attachment Content-Type Size
v13-0001-snapshot-scalability-Don-t-compute-global-horizo.patch text/x-diff 121.7 KB
v13-0002-snapshot-scalability-Move-PGXACT-xmin-back-to-PG.patch text/x-diff 20.3 KB
v13-0003-snapshot-scalability-Introduce-dense-array-of-in.patch text/x-diff 50.3 KB
v13-0004-snapshot-scalability-Move-PGXACT-vacuumFlags-to-.patch text/x-diff 17.5 KB
v13-0005-snapshot-scalability-Move-subxact-info-to-ProcGl.patch text/x-diff 26.2 KB
v13-0006-snapshot-scalability-cache-snapshots-using-a-xac.patch text/x-diff 11.1 KB

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