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@candle.pha.pa.us               |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026