On Fri, Feb 26, 2010 at 12:36 AM, Gokulakannan Somasundaram
<gokul007@gmail.com> wrote:
To be a bit more concrete: the typical sort of failure that you could
get from broken btree operators is failure of transitivity, that is
the comparators report A < B and B < C for some A, B, C, but do not say
that A < C when those two values are compared directly. I don't see any
convenient way to detect that as a byproduct of normal index operations,
because you wouldn't typically have a reason to make all three
comparisons in close proximity. Indeed, the searching and sorting
algorithms do their best to avoid making "redundant" comparisons of that
kind.
It definitely affects current indexes. We can't completely avoid bad user functions. That is why it is important to put limits on how much damage they can do. That's the motivation for the idea I mentioned before, of double-checking visibility data in an IndexTuple before letting it survive a VACUUM.
