Hannu Krosing <hannu@skype.net> writes:
> But if we do need to consider the kernel-level behaviour mentioned, then
> the whole PITR thing becomes an impossibility. Consider the case when we
> get a torn page during the initial copy with tar/cpio/rsync/whatever,
> and no WAL record updates it.
The only way the backup program could read a torn page is if the
database is writing that page concurrently, in which case there must
be a WAL record for the action.
This was all thought through carefully when the PITR mechanism was
designed, and it is solid -- as long as we are doing full-page writes.
Unfortunately, certain people forced that feature into 8.1 without
adequate review of the system's assumptions ...
regards, tom lane
