Re: tuple concurrently updated

How do you think about my suggestion to not versioning system catalogs?

p.s. It's unbelivable that I got a reply from legendary Tom Lane. :)

Best,
Kim.

"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote in message
news:20755(dot)1027628748(at)sss(dot)pgh(dot)pa(dot)us(dot)(dot)(dot)
> "Kangmo, Kim" <ilvsusie(at)hanafos(dot)com> writes:
> > If the index on the same class,
> > two concurrent CREATE INDEX command can update pg_class.relpages
> > at the same time.
>
> Or try to, anyway. The problem here is that the code that updates
> system catalogs is not prepared to cope with concurrent updates
> to the same tuple.
>
> > I guess that is not a bug of pgsql, but a weak point of
> > MVCC DBMS.
>
> No, it's not a limitation of MVCC per se, it's only an implementation
> shortcut for catalog updates. Fixing this across all system catalog
> updates seems more trouble than it's worth. It'd be nice if the
> concurrent-CREATE-INDEX case worked, though.
>
> regards, tom lane
>
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