Re: Automatic free space map filling

Ühel kenal päeval, R, 2006-03-03 kell 11:37, kirjutas Tom Lane:
> Alvaro Herrera <alvherre@commandprompt.com> writes:
> > So for you it would certainly help a lot to be able to vacuum the first
> > X pages of the big table, stop, release locks, create new transaction,
> > continue with the next X pages, lather, rinse, repeat.
> 
> > This is perfectly doable, it only needs enough motivation from a
> > knowledgeable person.
> 
> Bruce and I were discussing this the other day; it'd be pretty easy to
> make plain VACUUM start a fresh transaction immediately after it
> finishes a scan heap/clean indexes/clean heap cycle.  

Do you mean the full (scan heap/clean indexes/clean heap) cycle or some
smaller cycles inside each step ?

If you mean the full cycle, then it is probably not worth it, as even a
single 'clean index' pass can take hours on larger tables.

> The infrastructure
> for this (in particular, session-level locks that won't be lost by
> closing the xact) is all there.  You'd have to figure out how often to
> start a new xact ... every cycle is probably too often, at least for
> smaller maintenance_work_mem settings ... but it'd not be hard or
> involve any strange changes in system semantics.

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Hannu