Re: Intermittent buildfarm failures on wrasse

I wrote:
> the vacuum in test_setup sees
> ...
>         removable cutoff: 724, older by 26 xids when operation ended
> ...

BTW, before I forget: the wording of this log message is just awful.
On first sight, I thought that it meant that we'd computed OldestXmin
a second time and discovered that it advanced by 26 xids while the VACUUM
was running.  Looking at the code, I see that's not so:

            diff = (int32) (ReadNextTransactionId() - OldestXmin);
            appendStringInfo(&buf,
                             _("removable cutoff: %u, older by %d xids when operation ended\n"),
                             OldestXmin, diff);

but good luck understanding what it actually means from the message
text alone.  I think more appropriate wording would be something like

"removable cutoff: %u, which was %d xids old when operation ended\n"

Also, is it really our practice to spell XID in lower-case in
user-facing messages?

Thoughts, better ideas?

            regards, tom lane