Re: Increasing the length of pg_stat_activity.current_query...

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> Greg Stark <gsstark(at)mit(dot)edu> writes:
> > The pgstat messages are indeed fixed size.
>
> No, there's a fixed maximum size.

Hm. *rereads source*

It's true, pgstat_report_activity only sends the actual size of the query, not
the full payload size.

The only problem I see in raising the size of PGSTAT_MSG_PAYLOAD is that it
also governs the size of PGSTAT_NUM_TABPURGE and PGSTAT_NUM_TABENTRIES.
There's no need to grow those arrays and risk losing them. But these message
sizes could just be left based on the 1k value while boosting the maximum size
of PGSTAT_ACTIVITY_SIZE.

That would have no downside and only benefits. The worst case is that a
machine that didn't handle UDP fragment reassembly would drop the packets that
postgres is currently dropping preemptively. Shorter queries and other packets
would be unaffected.

--
greg