Re: online tape backup

Michael Monnerie <michael.monnerie@it-management.at> writes:
> From what I understand, if I run a vacuum, the WAL logs will be
> enormous, as they do not simply store the vacuum command itself, but
> every single operation done on the db.
> If that's true, running vacuum before the base backup could be better,
> as there are less WAL logs to store, making the backup smaller, right?

You're suffering from a fundamental misconception about the nature of WAL.
Vacuum doesn't "shrink WAL", and neither does anything else; WAL is a
history of every action ever taken in the database, and so a vacuum will
just add a bunch more to that history.

            regards, tom lane