Re: No heap lookups on index

David,

You can find some of this discussion in "Much Ado About COUNT(*)". Related
to that discussion, I had written a patch which added visibility information
to the indexes.

If you're interested in the patch and/or consulting, contact me offline.

-Jonah

On 1/18/06, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> David Scott <davids(at)apptechsys(dot)com> writes:
> > Is the additional overhead of keeping full tuple visibility
> > information inside of the index so odious to the Postgres community as
> > to prevent a patch with this solution from being applied back to the
> > head?
>
> This has been discussed and rejected before (multiple times). If you
> want it considered you'll have to present stronger arguments than have
> so far been made. The current consensus is that the probability of a
> net performance win is not good enough to justify the large amount of
> development effort that would be required.
>
> What sort of problems are you dealing with exactly? There has been
> some discussion of changes that would improve certain scenarios. For
> instance it might be plausible to do joins using index information and
> only go back to the heap for entries that appear to pass the join test.
>
> regards, tom lane
>
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