Re: ERROR: found unexpected null value in index

Peter Geoghegan <pg@bowt.ie> writes:
> On Wed, Jul 10, 2019 at 1:25 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I wonder if we'd be better off to switch over to using data directly
>> from the index entry, rather than trying to recover it from the heap.

> Maybe that problem has nothing to do with what you said, but I was
> reminded of the fact that it's far from clear how effective
> kill_prior_tuple actually is in the real world (i.e. with
> concurrency). I guess that your suggestion would make it even less
> likely that LP_DEAD hint bits would be set by
> get_actual_variable_range() scans, because there would be no
> opportunity to check the heap.

I was imagining it would still check the heap, if necessary, to verify
that it'd found a tuple passing the given snapshot.

> Wasn't one of the goals of commit
> 3ca930fc39c to make it more likely that extrema values would be killed
> by get_actual_variable_range() scans, for the benefit of future
> get_actual_variable_range() scans?

Yes, and my point was that we still need that effect in some form.  But
once we've found that there's a tuple that's "live enough" (for some
definition of that) we could pull the actual data from the index not heap.

            regards, tom lane