>
> On Sunday, December 16, 2001, at 11:42 AM, Stephan Szabo wrote:
>
> > On Sun, 16 Dec 2001, Terrence Brannon wrote:
> >
> >> The Momjian book is excellent (in spite of some of the bonehead
> >> reviews on amazon.com). I just finished the "Numbering Rows"
> >> section and have a few questions. None of these were in the FAQ,
> >> BTW.
> >>
> >> 1 - are OIDs ever re-used if rows are deleted?
> >
> > OIDs wraparound, but they don't just fill holes, so uniqueness
> > isn't guaranteed unless you have something like a unique index
> > on oid.
>
> Where do you get this information? If I am reading the Momjian
> book correctly, it disagrees with you:
>
> Every row in POSTGRESQL is assigned a unique, normally invisible
> number called an object identification number (OID). When the
> software is initialized with initdb?, 12.1 a counter is created
> and set to approximately seventeen-thousand. 12.2 The counter is
> used to uniquely number every row. Although databases may be
> created and destroyed, the counter continues to increase. It is
> used by all databases, so identification numbers are always
> unique. No two rows in any table or in any database will ever
> have the same object ID.
The book asssume you are not going to roll over the counter. Very large
installations have been concerned about such rollover after inserting >4
billion rows. We have not gotten any actual report of it happening, but
it could theoretically happen.
-- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610)
853-3000+ If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill,
Pennsylvania19026