Re: Per query FDW network stat collection

On Tue, Aug 24, 2021 at 5:12 PM Ilya Gladyshev
<i(dot)gladyshev(at)postgrespro(dot)ru> wrote:
>
> I have implemented per query network stat collection for FDW. It is done
> in a similar way to how buffer and WAL stats are collected and it can be
> seen with a new NETWORK option for explain command:
>
> explain (analyze, network) insert into itrtest values (2, 'blah');
>
> QUERY PLAN
> -----------------------------------------------------------------------------------------------
> Insert on itrtest (cost=0.00..0.01 rows=0 width=0) (actual
> time=0.544..0.544 rows=0 loops=1)
> Network: FDW bytes sent=197 received=72, wait_time=0.689
> [...]

It sound like a really useful metric to have.

However I'm not sure that having a new "network" option is the best
way for that. It seems confusing as IIUC it won't be catching all
network activity (like fe/be activity, or network disk...) but only
FDW activity. I think it would be better to have those information
retrieved when using the verbose option rather than a new one.
Similarly, I'm afraid that INSTRUMENT_NETWORK could be misleading,
although I don't have any better proposal right now.