On Mon, Oct 07, 2024 at 09:54:21AM +0000, Bertrand Drouvot wrote: > On Fri, Sep 20, 2024 at 01:26:49PM +0900, Michael Paquier wrote: >> This would rely on the fact that we would use the ProcNumber for the >> dshash key, and this information is not provided in pg_stat_activity. >> Perhaps we should add this information in pg_stat_activity so as it >> would be easily possible to do joins with a SQL function that returns >> a SRF with all the stats associated with a given connection slot >> (auxiliary or backend process)? > > I'm not sure that's needed. What has been done in the previous versions is > to get the stats based on the pid (see pg_stat_get_backend_io()) where the > procnumber is retrieved with something like > GetNumberFromPGProc(BackendPidGetProc(pid)).
Ah, I see. So you could just have the proc number in the key to control the upper-bound on the number of possible stats entries in the dshash. Assuming that none of this data is persisted to the stats file at shutdown and that the stats of a single entry are reset each time a new backend reuses a previous proc slot, that would be OK by me, I guess. >> The active PIDs of the live sessions are not stored in the active >> stats, why not? > > That was not needed. We can still retrieve the stats based on the pid thanks > to something like GetNumberFromPGProc(BackendPidGetProc(pid)) without having > to actually store the pid in the stats. I think that's fine because the pid > only matters at "display" time (pg_stat_get_backend_io()). Okay, per the above and the persistency of the stats. -- Michael
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