Simon Riggs <simon@2ndQuadrant.com> writes:
> On Fri, 2011-01-21 at 11:19 +0200, Heikki Linnakangas wrote:
>> 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.
No, that idea is DOA from a performance standpoint. We sweated blood to
avoid having to assign XIDs to read-only transactions, and we're not
going back. If SSI requires that, SSI is not getting committed.
regards, tom lane
