Re: Update on true serializable techniques in MVCC

Robert Haas escribió:
> On Wed, Dec 16, 2009 at 10:29 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > On Wednesday 16 December 2009 16:24:42 Robert Haas wrote:
> >> >   Inserts and deletes follow the same protocol, obtaining an exclusive
> >> >   lock on the row after the one being inserted or deleted. The result
> >> >   of this locking protocol is that a range scan prevents concurrent
> >> >   inserts or delete within the range of the scan, and vice versa.
> >> >
> >> > That sounds like it should actually work.
> >>
> >> Only if you can guarantee that the database will access the rows using
> >> some particular index.  If it gets to the data some other way it might
> >> accidentally circumvent the lock.  That's kind of a killer in terms of
> >> making this work for PostgreSQL.
> > Isnt the whole topic only relevant for writing access? There you have to
> > access the index anyway.
>
> Yeah, I guess you have to insert the new tuple. I guess while you
> were at it you might check whether the next tuple is locked...

So you'd have to disable HOT updates when true serializability was
active?

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Alvaro Herrera http://www.CommandPrompt.com/
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