Simon Riggs <simon@2ndquadrant.com> writes:
> The cause here is data changing underneath the user. Your patch solves
> the most obvious error, but it still allows other problems if applying
> the backup block changes data. If the backup block doesn't do anything
> at all then we don't need to apply it either.
This is nonsense. What applying the backup block does is to apply the
change that the WAL record would otherwise have applied, except we
decided to make it store a full-page image instead.
regards, tom lane