Re: Automatic free space map filling

On Mon, May 01, 2006 at 10:24:50PM +0200, Dawid Kuroczko wrote:
> VACUUM table WHERE some_col > now()-'1 hour'::interval;
>
> I.e. Let vacuum run "piggyback" on some index. This would allow
> for a quick vacuum of a fraction of a large table. Especially when
> the table is large, and only some data (new data) are being modified.
>
> The vacuum for such a table would:
> 1. scan the index accoriding to the where criteria and create bitmap
> of blocks to look at.
> 2. go through these blocks and vacuum them.
>
> Hmm, another perhaps silly idea -- a special index kind for tracking
> tuple deaths. Ie -- something like whenever tuple is updated/deleted,
> insert an entry into such index, using last session the tuple is visible
> for as a key. Then, perhaps, vacuum could scan such an index and
> find tuples which are candidates for removal. I lack the knowledge of
> PostgreSQL's internals, so forgive me if I am writing something
> completely insane. :)

There is a TODO to create a 'dead space map' which would cover #2 and
probably eliminate any use for #1.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461