On 2 May 2017 at 13:12, Simon Riggs <simon@2ndquadrant.com> wrote:
> What I suggest is that with logical decoding in mind we do this
> 1. Inject a new record XLOG_SNAPSHOT_START at the start of
> LogStandbySnapshot(). We start logical decoding from there.
> 2. Record any transactions that end
> 3. Now the full XLOG_RUNNING_XACTS record arrives. We apply all xacts
> that are seen as running, minus any ended between 1 and 3
>
> This avoids the problems for the race but without holding locks while
> we log XLOG_RUNNING_XACTS, something that was considered painful for
> Hot Standby.
Sounds like a sensible solution to me. It avoids the need for a rather
undesirable interlock between xlog and shmem commit.
-- Craig Ringer http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services
