> It has been suggested in past to add such a visibility to index
> tuple header so
> that index and heaps can be cleaned out of order. In such a case
> other backround
It seems to me that the benefit of this wouldn't be all that impressive
*when accessing the cache*, which is the problem this discussion is about.
Disk access would occur more commonly with large tables, which I'll ignore.
Let's say total scan time for a query on a very dirty table is 100ms. It
seems safe to assume that the scan time for the index would be *roughly*
half that of the heap. If visibilty could be determined by looking at just
the index tuple, you'd cut you query scan time down to 50ms. When the clean
table case is 7ms total scan time, the difference between 50 and 100 ms is
not much of an issue; either way, it's still way to high!
> However increasing index footprint seems to be a tough sell.
And rightly so, IMO.
Glen Parker