From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Stas Kelvich <s.kelvich@postgrespro.ru>
To: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Global snapshots
Date: Tue, 1 May 2018 22:58:37 -0400
Message-ID: <0cec343f-a50c-a40c-a299-a4043960e26c@2ndquadrant.com> (raw)
In-Reply-To: <21BC916B-80A1-43BF-8650-3363CCDAE09C@postgrespro.ru>
References: <21BC916B-80A1-43BF-8650-3363CCDAE09C@postgrespro.ru>
On 5/1/18 12:27, Stas Kelvich wrote:
> Clock-SI is described in [5] and here I provide a small overview, which
> supposedly should be enough to catch the idea. Assume that each node runs Commit
> Sequence Number (CSN) based visibility: database tracks one counter for each
> transaction start (xid) and another counter for each transaction commit (csn).
> In such setting, a snapshot is just a single number -- a copy of current CSN at
> the moment when the snapshot was taken. Visibility rules are boiled down to
> checking whether current tuple's CSN is less than our snapshot's csn. Also it
> worth of mentioning that for the last 5 years there is an active proposal to
> switch Postgres to CSN-based visibility [6].
But that proposal has so far not succeeded. How are you overcoming the
reasons for that?
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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To: pgsql-hackers@postgresql.org
Cc: peter.eisentraut@2ndquadrant.com, s.kelvich@postgrespro.ru
Subject: Re: Global snapshots
In-Reply-To: <0cec343f-a50c-a40c-a299-a4043960e26c@2ndquadrant.com>
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