Hello David, Thanks for your answer.
Le 23/01/2024 à 11:41, David Rowley a écrit :
If you're using psql, if you do \timing on, how long does EXPLAIN take without ANALYZE? That also goes through executor startup and shutdown.
You are absolutely correct : the EXPLAIN without ANALYZE gives about the same results. Also, minimizing the amount of workmem in postgresql.conf changes drastically the timings. So that means memory allocation is eating up a lot of time _PER_QUERY_ ?
Since we have quite some RAM on our machines, I dedicated as much as possible to workmem (initially I was allocating 1GB) but this looks quite counterproductive (I didn't think that memory was allocated every time, I thought it was "available" for the current query but not necessarily used). Is this an issue specific to that version of PostgreSQL? (I guess no) Or can this be hardware-related? Or OS-related (both systems on which I have done tests are running Ubuntu, I will try on Debian)?
Thanks again for your inputs. Best, JC
