Re: what to revert

On Wed, May 4, 2016 at 6:28 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2016-05-04 18:22:27 -0400, Robert Haas wrote:
>> On Wed, May 4, 2016 at 6:06 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> >> Some of the proposals involve fairly small tweaks to call
>> >> MaintainOldSnapshotTimeMapping() from elsewhere or only when
>> >> something changes (like crossing a minute boundary or seeing that a
>> >> new TransactionId has been assigned). If you can disentangle those
>> >> ideas, it might not look so bad.
>> >
>> > Yea, if we can do that, I'm ok. I'm doubtful about releasing with the
>> > current state, even leaving performance aside, since fixing this will
>> > result in somewhat changed semantics, and I'm doubtful about significant
>> > development at this point of the release process. If it comes down to
>> > either one of those I'm clearly in favor of the latter.
>>
>> How would the semantics change?
>
> Right now the time for computing the snapshot is relevant, if
> maintenance of xids is moved, it'll likely be tied to the time xids are
> assigned. That seems perfectly alright, but it'll change behaviour.

Not following.

>> So, I was worried about this, too. But I think there is an
>> overwhelming consensus on pgsql-release that getting a beta out early
>> trumps all, and that if that results in somewhat more post-beta1
>> change than we've traditionally had, so be it.
>
> *If* that's the policy - cool! I just don't want to see the issue
> not being fixed due to only wanting conservative changes. And the
> discussion around fixing spinlock related issues in the patch certainly
> made me think the RMT aimed to be conservative.

Understand that I am conveying what I understand the sentiment of the
community to be, not guaranteeing any specific outcome.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company