On Mon, 2023-11-13 at 17:06 -0800, Benjamin Leis wrote:
> I'm looking at a pg_stat_activity dump where there are a group of active
> threads stuck for a long time in MessageQueueSend
> 7:52.394089+00 | IPC | MessageQueueSend | active |
> | 27406510 | -5892847938856697008 | SELECT ....
> Does this mean they are blocked on clients reading data or does it
> represent something blocking on the server side?
That's something on the server: a parallel worker process is waiting to
send data to the parallel leader process. Look for the "leader_pid" column
in the "pg_stat_activity" line above and see what that process is doing.
I wouldn't worry about a parellel worker in that state, as long as there
is no problem with the parallel leader.
Yours,
Laurenz Albe