Re: ctid access is slow

--- "Jim C. Nasby" <jnasby(at)pervasive(dot)com> wrote:

> On Wed, Aug 24, 2005 at 09:26:10AM +0930, Jeff
> Eckermann wrote:
> > The ctid value can be useful in a multi user
> application, to check whether a
> > record has been changed by another user, before
> committing changes.
> > Whenever a record is updated the ctid value will
> be changed, so by storing
> > the ctid value when first fetching the record,
> that can be compared with the
> > current ctid value before doing the update.
>
> I believe that's not necessarily true. If you select
> a tuple and it's
> ctid and it's updated more than once with a vacuum
> in-between I believe
> it could end up back in the same position, which
> would mean the same
> ctid.

True. But the probability of that happening would
generally be low enough not to bother the designers of
most applications.

> --
> Jim C. Nasby, Sr. Engineering Consultant
> jnasby(at)pervasive(dot)com
> Pervasive Software http://pervasive.com
> 512-569-9461
>

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