Re: SSI and Hot Standby

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