Re: Re: [COMMITTERS] pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold <

On 2016-04-13 08:36:47 -0400, Robert Haas wrote:
> I think that a significant performance regression which affects people
> not using snapshot_too_old would be a stop-ship issue, but I disagree
> that an issue which only affects people using the feature is a
> must-fix. It may be desirable to fix it, but I don't think we should
> regard it as a hard requirement. It's reasonable to fix some kinds of
> issues after feature freeze, but not at the price of accepting
> arbitrary amounts of new code that may have problems of its own.
> Every release will have some warts.

My problem with that is that snapshot-too-old is essentially a
efficiency feature for busy and large databases. Regressing noticeably
when it's enabled in it's natural habitat seems sad.

> Of course, the real fly in the ointment here is what we're going to do
> with the atomics once we have them. But AFAICS, there's no patch for
> that, yet. I don't think that I wish to take a position on whether a
> patch that hasn't been written yet should be applied. So I think the
> next step is that you should post the patches that you think should be
> applied in final form and those should be reviewed by knowledgeable
> people. Then, based on those reviews, the RMT can decide what to do.

Well, I'm less likely to write a patch when there's no chance that it's
going to be applied. Which the rest of the thread sounds like...

Greetings,

Andres Freund