Attached is a patch to remove the lock protection for
HeapTupleSatisfiesVacuum() in index code. The basic idea is: if we can do
a pin/lock/unlock sequence on a page, then without locking again, we are
gauranteed that there is no vacuum process acting on the same page.
According to buffer pool access rule #4, we then can examine/change the
hints bit safely.
Regards,
Qingqing
