Simon Riggs wrote:
On Fri, 2009-05-15 at 22:56 +0900, Fujii Masao wrote:
OK, I probably understood your point. The timeline history files whose
timeline ID is larger than that of an oldest backup must not be deleted
from the archive. On the other hand, the smaller or equal one can be
deleted. Not all history files are necessary. So, if we don't keep older
backup, we probably can delete all files in the archive before
pg_start_backup().
Is my understanding right?
Heikki is right in one sense: if you do pg_start_backup() then for
*that* backup you do not need earlier files.
However, as you have pointed out, if you have *multiple* backups then
deleting history files may cause problems with an earlier backup.
It's standard practice to have >1 backup, so there is potential for
error and minimum is we must document that.
Rather than explaining the problem and the rules by which we can work
out exactly which history files to keep, I think it is safer to say that
we must keep all history files.
This whole area is unfortunately way too fragile. We need some way of
managing these facilities that hides a lot of these details and is
therefore less likely to produce shot feet, IMNSHO. I get very nervous
every time I have to touch it.
cheers
andrew
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