| From: | Craig Ringer <craig(at)2ndquadrant(dot)com> |
|---|---|
| To: | Bruce Momjian <bruce(at)momjian(dot)us> |
| Cc: | Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Kevin Grittner <kgrittn(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Alfred Perlstein <alfred(at)freebsd(dot)org>, Geoff Winkless <pgsqladmin(at)geoff(dot)dj>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Why we lost Uber as a user |
| Date: | 2016-08-17 14:39:16 |
| Message-ID: | CAMsr+YEej2hxCoz965E4cvRyCk=2rOSf910U0Gtyzso7VhqVww@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 17 August 2016 at 21:35, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>
> > I saw from the Uber article that they weren't going to per-row logical
> > replication but _statement_ replication, which is very hard to do
> > because typical SQL doesn't record what concurrent transactions
> > committed before a new statement's transaction snapshot is taken, and
> > doesn't record lock order for row updates blocked by concurrent activity
> > --- both of which affect the final result from the query.
>
> I assume they can do SQL-level replication when there is no other
> concurrent activity on the table, and row-based in other cases?
I don't know, but wouldn't want to assume that. A quick search suggests
they probably define that away as nondeterministic behaviour that's allowed
to cause master/replica differences, but no time to look deeply.
--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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