| From: | Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru> |
|---|---|
| To: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Jeff Davis <pgsql(at)j-davis(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Greg Stark <stark(at)mit(dot)edu>, Andres Freund <andres(at)2ndquadrant(dot)com>, Rajeev rastogi <rajeev(dot)rastogi(at)huawei(dot)com>, Markus Wanner <markus(at)bluegap(dot)ch>, Ants Aasma <ants(at)cybertec(dot)at>, Bruce Momjian <bruce(at)momjian(dot)us>, obartunov <obartunov(at)postgrespro(dot)ru>, Teodor Sigaev <teodor(at)postgrespro(dot)ru> |
| Subject: | Re: Proposal for CSN based snapshots |
| Date: | 2016-08-10 13:34:38 |
| Message-ID: | CAPpHfdsGqb1EtmWo7wJZz=TXaBM_xwAEhfr-nNG8+c57Tm_cbQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Aug 9, 2016 at 3:16 PM, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
> (Reviving an old thread)
>
> I spent some time dusting off this old patch, to implement CSN snapshots.
> Attached is a new patch, rebased over current master, and with tons of
> comments etc. cleaned up. There's more work to be done here, I'm posting
> this to let people know I'm working on this again. And to have a backup on
> the 'net :-).
>
Great! It's very nice seeing that you're working on this patch.
After PGCON I've your patch rebased to the master, but you already did much
more.
> I switched to using a separate counter for CSNs. CSN is no longer the same
> as the commit WAL record's LSN. While I liked the conceptual simplicity of
> CSN == LSN a lot, and the fact that the standby would see the same commit
> order as master, I couldn't figure out how to make async commits to work.
>
I didn't get async commits problem at first glance. AFAICS, the difference
between sync commit and async is only that async commit doesn't wait WAL
log to flush. But async commit still receives LSN.
Could you describe it in more details?
------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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