Re: why there is not VACUUM FULL CONCURRENTLY?

Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:

> On 2024-Dec-11, Antonin Houska wrote:
>
> > Oh, it was too messy. I think I was thinking of too many things at once (such
> > as locking the old heap, the new heap and the new heap's TOAST). Also, one
> > thing that might have contributed to the confusion is that make_new_heap() has
> > the 'lockmode' argument, which receives various values from various
> > callers. However, both the new heap and its TOAST relation are eventually
> > created by heap_create_with_catalog(), and this function always leaves the new
> > relation locked in AccessExclusiveMode. Maybe this needs some refactoring.
> >
> > Therefore I reverted the changes arount make_new_heap() and simply pass NoLock
> > for lockmode in cluster.c
>
> Cool, thanks, I have pushed this. I made some additional minor changes,
> nothing earth-shattering.

It seems you accidentally fixed another problem :-) I was referring to the
'lockmode' argument of make_new_heap(). I can try to write a patch for that
but ...

> Meanwhile the patch 0004 has some seemingly trivial conflicts. If you
> want to rebase, I'd appreciate that. In the meantime I'll give a look
> at the next two other API changes.

... I can apply v06 even though I do have the commit ebd8fc7e47 in my working
tree. (And the CF bot does not complain (yet?).) Have you removed the
'lockmode' argument also from make_new_heap() and forgot to push it? This
change would probably cause a conflict with v06.

> I'm not happy with the idea of having this new command be VACUUM (FULL
> CONCURRENTLY). It's a bit of an absurd name if you ask me. Heck, even
> VACUUM (FULL) seems a bit absurd nowadays.
>
> Maybe we should have a new toplevel command. Some ideas that have been
> thrown around:
>
> - RETABLE (it's like REINDEX, but for tables)
> - ALTER TABLE <tab> SQUEEZE
> - SQUEEZE <table>
> - VACUUM (SQUEEZE)
> - VACUUM (COMPACT)
> - MAINTAIN <tab> COMPACT
> - MAINTAIN <tab> SQUEEZE

I recall that DB2 has REORG command, which also can do clustering [1]

Regardless the name of the new command, should that also handle the
non-concurrent cases? In that case we'd probably need to mark CLUSTER and
VACUUM (FULL) as deprecated.

[1] https://www.ibm.com/docs/en/db2/12.1?topic=commands-reorg-table

--
Antonin Houska
Web: https://www.cybertec-postgresql.com