Re: Vacuum questions

"Chris Hoover" <revoohc(at)sermonaudio(dot)com> writes:
> We have also had one test occurrence where after the upgrade, a vacuum
> full would not recover the space. However, when we bounced the
> postmaster, and then performed a vacuum full, the space was recovered.
> Any ideas on what might cause this?

Most likely, you had an open transaction lurking that was old enough
that it could still "see" the deleted data, and so VACUUM couldn't
safely reclaim the data.

VACUUM's decisions about this are cluster-wide; so even though you'd
recently created the database in question, a long-running transaction
in another database under the same postmaster could still cause the
problem.

regards, tom lane