Re: Heikki Linnakangas 2014-02-13 <52FCD02C.3060201@vmware.com>
> >Is removing the "test ! -f" part and hence overwriting files in the
> >archive safe, i.e. are the files the same?
>
> No. Not in general, anyway. If the old master keeps running, even
> for a moment, after the partial file was copied, it will have
> created more WAL records which are present in the old master's copy
> of the segment, but not in the standby's.
So why does PostgreSQL then ever try to archive something from the old
timeline? Isn't overwriting files on the old timeline just a very bad
idea in general? If so, it shouldn't be the responsibility of
archive_command to prevent this, but the server shouldn't be trying
that in the first place.
> You could perhaps use "diff" as part of archive_command, to check if
> archived version is identical to the one about to be archived.
Well, if that makes it into the default postgresql.conf (and docs)...
Otoh, it's still not nice that this could still be an archive command
that fails, i.e. requires admin intervention before archiving can
proceed.
Mit freundlichen Grüßen,
Christoph Berg
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