Re: vacuum, performance, and MVCC

On Mon, Jun 26, 2006 at 07:17:31AM -0400, Bruce Momjian wrote:
> Correct!  We use the same pointers used by normal UPDATEs, except we set
> a bit on the old tuple indicating it is a single-index tuple, and we
> don't create index entries for the new tuple.  Index scan routines will
> need to be taught about the new chains, but because only one tuple in
> the chain is visible to a single backend, the callers should not need to
> be modified.

I suppose we would also change the index_getmulti() function to return
a set of ctids plus flags so the caller knows to follow the chains,
right? And for bitmap index scans you would only remember the page in
the case of such a tuple, since you can't be sure the exact ctid you've
got is the one you want.

Seems doable.

Have a nice day,
--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.