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@sss.pgh.pa.us> wrote in message
news:20755.1027628748@sss.pgh.pa.us...
> "Kangmo, Kim" <ilvsusie@hanafos.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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