Re: Automatic free space map filling

On Thu, Mar 02, 2006 at 08:33:46AM -0500, Christopher Browne wrote:
> What is unclear to me in the discussion is whether or not this is
> invalidating the item on the TODO list...
>
> -------------------
> Create a bitmap of pages that need vacuuming

<snip>

I think this is doable, and not invalidated by anything said so far.
All this is changeing is whether to scan the whole table or just the
bits changed. Unfortunatly I don't think you can avoid scanning the
indexes :(.

Note, for this purpose you don't need to keep a bit per page. The
OS I/O system will load 64k+ (8+ pages) in one go so one bit per 8
pages would be sufficient.

The inverse is keep a list of pages where we know all tuples are
visible to everyone. I'm not sure if this can be done race condition
free. ISTM it would be possible to get the new Bitmap Index Scans to
avoid checking visiblity straight away but wait until it has been
AND/OR'd with other bitmaps and only at the end checking visibility.
But maybe that already happens...

Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.