Re: Suspicious behaviour on applying XLOG_HEAP2_VISIBLE.

On 2016-04-14 11:50:58 -0400, Robert Haas wrote:
> On Wed, Apr 13, 2016 at 9:58 PM, Andres Freund <andres@anarazel.de> wrote:
> > We've recently discussed a very similar issue around
> > http://www.postgresql.org/message-id/20160227002958.peftvmcx4dxwe244@alap3.anarazel.de
> >
> > Unfortunately Simon over in that thread disagreed there about fixing
> > this by always emitting a commit record when nmsgs > 0 in
> > RecordTransactionCommit().  I think this thread is a pretty strong hint
> > that we actually should do so.
> 
> Yes.  I'm pretty confident that you had the right idea there, and that
> Simon's objection was off-base.

The easiest way to achieve that seems to be to just assign an xid if
that's the case; while it's not necessarily safe/efficient to do so at
the point the invalidation message was queued, I think it should be safe
to do so at commit time. Seems less invasive to backpatch than to either
support commit records without xids, or a separate record just
transporting invalidation messages.

Although a separate record with invalidations is going to be needed to
support logical decoding of running xacts anyway...

- Andres