Re: HOT chain validation in verify_heapam()

But here's one random idea: add a successor[] array and an lp_valid[]
array. In the first loop, set lp_valid[offset] = true if it passes the
check_lp() checks, and set successor[A] = B if A redirects to B or has
a CTID link to B, without matching xmin/xmax. Then, in a second loop,
iterate over the successor[] array. If successor[A] = B && lp_valid[A]
&& lp_valid[B], then check whether A.xmax = B.xmin; if so, then
complain if predecessor[B] is already set, else set predecessor[B] =
A. Then, in the third loop, iterate over the predecessor array just as
you're doing now. Then it's clear that we do the lp_valid checks
exactly once for every offset that might need them, and in order. And
it's also clear that the predecessor-based checks can never happen
unless the lp_valid checks passed for both of the offsets involved.