Use of RangeVar for partitioned tables in autovacuum

Hi all,

I have been looking more closely at the problem in $subject, that I
have mentioned a couple of times, like here:
https://www.postgresql.org/message-id/CAB7nPqQa37OUne_rJzpmWC4EXQaLX9f27-Ma_-rSFL_3mj+HFQ@mail.gmail.com

As of HEAD, the RangeVar defined in calls of vacuum() is used for
error reporting, only in two cases: for autoanalyze and autovacuum
when reporting to users that a lock cannot be taken on a relation. The
thing is that autovacuum has the good idea to call vacuum() on only
one relation at the same time, with always a relation OID and a
RangeVar defined, so the code currently on HEAD is basically fine with
its error reporting, because get_rel_oids() will always work on the
relation OID with its RangeVar, and because code paths with manual
VACUUMs don't use the RangeVar for any reports.

While v10 is safe, I think that this is wrong in the long-term and
that may be a cause of bugs if people begin to generate reports for
manual VACUUMs, which is plausible in my opinion. The patch attached,
is what one solution would look like if we would like to make things
more robust as long as manual VACUUM commands can only specify one
relation at the same time. I have found that tracking the parent OID
by tweaking a bit get_rel_oids() was the most elegant solution. Please
note that this range of problems is something that I think is better
solved with the infrastructure that support for VACUUM with multiple
relations includes (last version here
https://www.postgresql.org/message-id/766556DD-AA3C-42F7-ACF4-5DC97F41F151@amazon.com).
So I don't think that the patch attached should be integrated, still I
am attaching it to satisfy the curiosity of anybody looking at this
message.

In conclusion, I think that the open item of $subject should be
removed from the list, and we should try to get the multi-VACUUM patch
in to cover any future problems. I'll do so if there are no
objections.

One comment on top of vacuum() is wrong by the way: in the case of a
manual VACUUM or ANALYZE, a NULL RangeVar is used if no relation is
specified in the command.

Thanks,
--
Michael