| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
| Cc: | Dan Ports <drkp(at)csail(dot)mit(dot)edu>, Florian Pflug <fgp(at)phlo(dot)org>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: SSI and Hot Standby |
| Date: | 2011-01-21 10:00:54 |
| Message-ID: | 1295604054.1803.9502.camel@ebony |
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| Lists: | pgsql-hackers |
On Fri, 2011-01-21 at 11:19 +0200, Heikki Linnakangas wrote:
> On 21.01.2011 11:10, Simon Riggs wrote:
> > So any xid that commits in a different sequence to the order in which
> > the xid was assigned creates a potential for unserialization? Or?
>
> It's not the order in which the xid was assigned that matters, but the
> order the transactions started and got their snapshots. The xids might
> be assigned a lot later, after the transactions have already read data.
So if a read-write transaction assigns an xid before it takes a snapshot
then we'll be OK? That seems much easier to arrange than passing chunks
of snapshot data backwards and forwards. Optionally.
--
Simon Riggs http://www.2ndQuadrant.com/books/
PostgreSQL Development, 24x7 Support, Training and Services
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