Re: System username in pg_stat_activity

Hi,

On 2024-02-16 21:41:41 +0100, Magnus Hagander wrote:
> > Maybe I am missing something, but why aren't we just getting the value from
> > the leader's entry, instead of copying it?
>
> The answer to that would be "because I didn't think of it" :)

:)


> Were you thinking of something like the attached?

> @@ -435,6 +438,22 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
>                  {
>                      values[29] = Int32GetDatum(leader->pid);
>                      nulls[29] = false;
> +
> +                    /*
> +                     * The authenticated user in a parallel worker is the same as the one in
> +                     * the leader, so look it up there.
> +                     */
> +                    if (leader->backendId)
> +                    {
> +                        LocalPgBackendStatus *leaderstat =
pgstat_get_local_beentry_by_backend_id(leader->backendId);
> +
> +                        if (leaderstat->backendStatus.st_auth_method != uaReject &&
leaderstat->backendStatus.st_auth_method!= uaImplicitReject)
 
> +                        {
> +                            nulls[31] = nulls[32] = false;
> +                            values[31] =
CStringGetTextDatum(hba_authname(leaderstat->backendStatus.st_auth_method));
> +                            values[32] = CStringGetTextDatum(leaderstat->backendStatus.st_auth_identity);
> +                        }
> +                    }

Mostly, yes.

I only skimmed the patch, but it sure looks to me that we could end up with
none of the branches setting 31,32, so I think you'd have to make sure to
handle that case.

Greetings,

Andres Freund