Robert Haas <robertmhaas@gmail.com> writes:
> No, I wasn't thinking about a tuple descriptor mismatch. I was
> imagining that the page contents themselves might be in flux while
> we're trying to read from it.
Oh, gotcha. Yes, that's a horribly plausible idea. All it'd take is
one WAL replay routine that hasn't been upgraded to acquire sufficient
buffer locks. Pre-hot-standby, there was no reason for them to be
careful about locking.
On the other hand, if that were the cause, you'd expect the symptoms
to be a bit more variable...
regards, tom lane
