Re: is pg_stat_activity "transactional"? How fast does it update?

On 6/10/25 08:46, Dominique Devienne wrote:
> On Tue, Jun 10, 2025 at 4:27 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Dominique Devienne <ddevienne(at)gmail(dot)com> writes:
>>> So when and how fast does pg_stat_activity update, in the face of a
>>> PQfinish?
>>
>> The shared state underlying pg_stat_activity is updated
>> immediately when something changes. However ...
>>
>> PQfinish is asynchronous: it sends a "goodbye" message and then
>> closes the connection without waiting for a response. So
>> depending on system load, the associated backend could still be
>> alive for some milliseconds. There might be other client
>> libraries that do that differently.
>>
>> Another thing that might be biting you is that a backend inspecting
>> pg_stat_activity() takes a snapshot of the view's contents and then
>> holds onto that snapshot until end of transaction. You can get
>> around that with pg_stat_clear_snapshot().
>
> Many thanks Tom. Didn't know either of those facts. --DD
>

For more detail see:

https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-STATS-VIEWS

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com