Re: [HACKERS] getting rid of SnapshotNow

On Fri, Jul 19, 2013 at 12:29 PM, Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:
> Robert Haas escribió:
>> On Fri, Jul 19, 2013 at 1:27 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
>> > Why not tell people to use SnapshotDirty if they need a
>> > not-guaranteed-consistent result?  At least then it's pretty obvious
>> > that you're getting some randomness in with your news.
>
>> On further reflection, I think perhaps pgrowlocks should just register
>> a fresh MVCC snapshot and use that.  Using SnapshotDirty would return
>> TIDs of unseen tuples, which does not seem to be what is wanted there.
>
> I think seeing otherwise invisible rows is useful in pgrowlocks.  It
> helps observe the effects on tuples written by concurrent transactions
> during experimentation.  But then, maybe this functionality belongs in
> pageinspect instead.

It does seem like it should be useful, at least as an option.  But I
feel like changing that ought to be separate from getting rid of
SnapshotNow.  It seems like too big of a behavior change to pass off
as a harmless tweak.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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