Skip site navigation (1) Skip section navigation (2)

Re: cheaper snapshots

From: Ants Aasma <ants(dot)aasma(at)eesti(dot)ee>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Hannu Krosing <hannu(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: cheaper snapshots
Date: 2011-07-29 00:12:07
Message-ID: CA+CSw_tei7BdWmpJOPieW=L3wn3rr298FUp_H=BbfpT6tA=RkA@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Fri, Jul 29, 2011 at 2:20 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> Well, again, there are three levels:
>
> (A) synchronous_commit=off.  No waiting!
> (B) synchronous_commit=local transactions, and synchronous_commit=on
> transactions when sync rep is not in use.  Wait for xlog flush.
> (C) synchronous_commit=on transactions when sync rep IS in use.  Wait
> for xlog flush and replication.
...
> So basically, you can't be more asynchronous than the guy in front of
> you.

(A) still gives a guarantee - transactions that begin after the commit
returns see
the commited transaction. A weaker variant would say that if the commit
returns, and the server doesn't crash in the meantime, the commit would at
some point become visible. Maybe even that transactions that begin after the
commit returns become visible after that commit.

--
Ants Aasma

In response to

Responses

pgsql-hackers by date

Next:From: Robert HaasDate: 2011-07-29 00:14:53
Subject: Re: cheaper snapshots
Previous:From: Ants AasmaDate: 2011-07-28 23:54:13
Subject: Re: cheaper snapshots

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group