Re: tests against running server occasionally fail, postgres_fdw & tenk1

Hi,

On 2023-02-08 18:37:41 -0800, Peter Geoghegan wrote:
> On Wed, Feb 8, 2023 at 4:29 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > 2) Add a message to lazy_vacuum() or lazy_vacuum_all_indexes(), that includes
> > - num_index_scans
> > - how many indexes we'll scan
> > - how many dead tids we're working on removing
>
> It's not obvious how you can know the number of index scans at this
> point. Well, it depends on how you define "index scan".

What I mean is to show the number of times we've done lazy_vacuum() so far,
although probably 1 based. Particularly if we do implement my proposal to
turn up verbosity once we're doing more than one pass, that'll allow at least
some insight to how bad things are from the log.

> This is a good thing for performance, of course, but it also makes VACUUM
> VERBOSE show information that makes sense to users, since things actually
> happen in a way that makes a lot more sense. I'm quite happy about the fact
> that the new VACUUM VERBOSE allows users to mostly ignore obscure details
> like whether an index was scanned by amvacuumcleanup() or by ambulkdelete()
> -- stuff that basically nobody understands. That seems worth preserving.

I don't mind making the messages as similar as possible, but I do mind if I as
a postgres hacker, or an expert consultant, can't parse that detail out. We
need to be able to debug things like amvacuumcleanup() doing too much work too
often.

> As I said, I don't mind making VACUUM VERBOSE behave a little bit more
> like a progress indicator, which is how it used to work. Maybe I went
> a little too far in the direction of neatly summarizing the whole
> VACUUM operation in one go. But I doubt that I went too far with it by
> all that much. Overall, the old VACUUM VERBOSE was extremely hard to
> use, and was poorly maintained -- let's not go back to that. (See
> commit ec196930 for evidence of how sloppily it was maintained.)

I don't want to go back to that either, as I said I mostly like the new
output.

Greetings,

Andres Freund