Re: strange error reporting

On Wed, Jan 20, 2021 at 12:19 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > I just made the mistake of trying to run pgbench without first running
> > createdb and got this:
>
> > pgbench: error: connection to database "" failed: could not connect to
> > socket "/tmp/.s.PGSQL.5432": FATAL: database "rhaas" does not exist
>
> > This looks pretty bogus because (1) I was not attempting to connect to
> > a database whose name is the empty string and (2) saying that it
> > couldn't connect to the socket is wrong, else it would not also be
> > showing a server message.
>
> I'm not sure about the empty DB name in the first part (presumably
> that's from pgbench, so what was your pgbench command exactly?).

I think it was just 'pgbench -i 40'. For sure, I didn't specify a database name.

> But the 'could not connect to socket' part is a consequence of my
> recent fiddling with libpq's connection failure reporting, see
> 52a10224e. We could discuss exactly how that ought to be spelled,
> but the idea is to consistently identify the host that we were trying
> to connect to. If you have a multi-host connection string, it's
> conceivable that "rhaas" exists on some of those hosts and not others,
> so I do not think the info is irrelevant.

I'm not saying that which socket I used is totally irrelevant although
in most cases it's going to be a lot of detail. I'm just saying that,
at least for me, when you say you can't connect to a socket, I at
least think about the return value of connect(2), which was clearly 0
here.

> Just looking at this, I wonder if we ought to drop pgbench's
> contribution to the message entirely; it seems like libpq's
> message is now fairly freestanding.

Maybe it would be better if it said:

connection to database at socket "/tmp/.s.PGSQL.5432" failed: FATAL:
database "rhaas" does not exist

--
Robert Haas
EDB: http://www.enterprisedb.com