On Thu, Apr 14, 2016 at 12:11 PM, Andres Freund <andres@anarazel.de> wrote:
> 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.
I agree that's better for back-patching. I hope it won't suck
performance-wise. In master, we might think of inventing something
new.
--
Robert Haas
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