Re: Proposal for CSN based snapshots

On 06/18/2014 12:41 AM, Robert Haas wrote:
> On Mon, Jun 16, 2014 at 12:58 AM, Craig Ringer <craig@2ndquadrant.com> wrote:
>> > On 05/30/2014 11:14 PM, Heikki Linnakangas wrote:
>>> >> Yeah. To recap, the failure mode is that if the master crashes and
>>> >> restarts, the transaction becomes visible in the master even though it
>>> >> was never replicated.
>> >
>> > Wouldn't another pg_clog bit for the transaction be able to sort that out?
> How?

A flag to indicate that the tx is locally committed but hasn't been
confirmed by a streaming synchronous replica, so it must not become
visible until the replica confirms it or SR is disabled.

Then scan pg_clog on start / replica connect and ask the replica to
confirm local commit for those tx's.

No?

-- Craig Ringer                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services