Re: Feature improvement: can we add queryId for pg_catalog.pg_stat_activity view?

On Thu, Apr 8, 2021 at 08:47:48AM +0800, Julien Rouhaud wrote:
> On Wed, Apr 07, 2021 at 07:38:35PM -0400, Bruce Momjian wrote:
> > On Wed, Apr 7, 2021 at 07:01:25PM -0400, Tom Lane wrote:
> > > Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > > > Uh, I think your patch missed a few things. First, you use "%zd"
> > > > (size_t) for the printf string, but calls to pgstat_get_my_queryid() in
> > > > src/backend/utils/error/elog.c used "%ld". Which is correct? I see
> > > > pgstat_get_my_queryid() as returning uint64, but I didn't think a uint64
> > > > fits in a BIGINT SQL column.
> > >
> > > Neither is correct. Project standard these days for printing [u]int64
> > > is to write "%lld" or "%llu", with an explicit (long long) cast on
> > > the printf argument.
> >
> > Yep, got it. The attached patch fixes all the calls to use %lld, and
> > adds casts. In implementing cvslog, I noticed that internally we pass
> > the hash as uint64, but output as int64, which I think is a requirement
> > for how pg_stat_statements has output it, and the use of bigint. Is
> > that OK?
>
> Indeed, this is due to how we expose the value in SQL. The original discussion
> is at
> https://www.postgresql.org/message-id/CAH2-WzkueMfAmY3onoXLi+g67SJoKY65Cg9Z1QOhSyhCEU8w3g@mail.gmail.com.
> As far as I know this is OK, as we want to show consistent values everywhere.

OK, yes, I do remember the discussion. I was wondering if there should
be a C comment about this anywhere.

> > I am also confused about the inconsistency of calling the GUC
> > compute_query_id (with underscore), but pg_stat_activity.queryid. If we
> > make it pg_stat_activity.query_id, it doesn't match most of the other
> > *id columsns in the table, leader_pid, usesysid, backend_xid. Is that
> > OK?I know I suggested pg_stat_activity.query_id, but maybe I was wrong.
>
> Mmm, most of the columns in pg_stat_activity do have a "_", so using query_id
> would make more sense.

OK, let me work on a patch to change that part.

> @@ -2967,6 +2967,10 @@ write_csvlog(ErrorData *edata)
>
> appendStringInfoChar(&buf, '\n');
>
> + /* query id */
> + appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_queryid());
> + appendStringInfoChar(&buf, ',');
> +
>
> /* If in the syslogger process, try to write messages direct to file */
> if (MyBackendType == B_LOGGER)
> write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
>
> Unless I'm missing something this will output the query id in the next log
> line? The new code should be added before the newline is output, and the comma
> should also be output before the queryid.

Yes, correct, updated patch attached.

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

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