Adding index flag showing tuple status

I am looking at adding an index tuple flag to indicate when a heap tuple
is expired so the index code can skip looking up the heap tuple.

The problem is that I can't figure out how be sure that the heap tuple
doesn't need to be looked at by _any_ backend. Right now, we update the
transaction commit flags in the heap tuple to prevent a pg_log lookup,
but that is not enough because some transactions may still see that heap
tuple as visible.

Vacuum has a complex test that looks a currently running transactions
and stuff. Do I have to duplicate that test in the new code? Seems I
do.

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026